The goal of this documentation is to comprehensively explain the Node.js\nAPI, both from a reference as well as a conceptual point of view. Each\nsection describes a built-in module or high-level concept.
\nWhere appropriate, property types, method arguments, and the arguments\nprovided to event handlers are detailed in a list underneath the topic\nheading.
", "miscs": [ { "textRaw": "Contributing", "name": "contributing", "desc": "If errors are found in this documentation, please submit an issue\nor see the contributing guide for directions on how to submit a patch.
\nEvery file is generated based on the corresponding .md file in the\ndoc/api/ folder in Node.js's source tree. The documentation is generated\nusing the tools/doc/generate.js program. An HTML template is located at\ndoc/template.html.
Throughout the documentation are indications of a section's\nstability. The Node.js API is still somewhat changing, and as it\nmatures, certain parts are more reliable than others. Some are so\nproven, and so relied upon, that they are unlikely to ever change at\nall. Others are brand new and experimental, or known to be hazardous\nand in the process of being redesigned.
\nThe stability indices are as follows:
\n\n\n\nStability: 0 - Deprecated. The feature may emit warnings. Backward\ncompatibility is not guaranteed.
\n
\n\n\nStability: 1 - Experimental. This feature is still under active development\nand subject to non-backward compatible changes or removal in any future\nversion. Use of the feature is not recommended in production environments.\nExperimental features are not subject to the Node.js Semantic Versioning\nmodel.
\n
\n\nStability: 2 - Stable. Compatibility with the npm ecosystem is a high\npriority.
\n
Caution must be used when making use of Experimental features, particularly\nwithin modules that may be used as dependencies (or dependencies of\ndependencies) within a Node.js application. End users may not be aware that\nexperimental features are being used, and therefore may experience unexpected\nfailures or behavior changes when API modifications occur. To help avoid such\nsurprises, Experimental features may require a command-line flag to\nexplicitly enable them, or may cause a process warning to be emitted.\nBy default, such warnings are printed to stderr and may be handled by\nattaching a listener to the 'warning' event.
Every .html document has a corresponding .json document presenting\nthe same information in a structured manner. This feature is\nexperimental, and added for the benefit of IDEs and other utilities that\nwish to do programmatic things with the documentation.
System calls like open(2) and read(2) define the interface between user programs\nand the underlying operating system. Node.js functions\nwhich simply wrap a syscall,\nlike fs.open(), will document that. The docs link to the corresponding man\npages (short for manual pages) which describe how the syscalls work.
Most Unix syscalls have Windows equivalents, but behavior may differ on Windows\nrelative to Linux and macOS. For an example of the subtle ways in which it's\nsometimes impossible to replace Unix syscall semantics on Windows, see Node.js\nissue 4760.
", "type": "misc", "displayName": "Syscalls and man pages" } ] }, { "textRaw": "Usage", "name": "Usage", "introduced_in": "v0.10.0", "type": "misc", "desc": "node [options] [V8 options] [script.js | -e \"script\" | - ] [arguments]
Please see the Command Line Options document for information about\ndifferent options and ways to run scripts with Node.js.
\nAn example of a web server written with Node.js which responds with\n'Hello, World!':
Commands displayed in this document are shown starting with $ or >\nto replicate how they would appear in a user's terminal.\nDo not include the $ and > characters. They are there to\nindicate the start of each command.
There are many tutorials and examples that follow this\nconvention: $ or > for commands run as a regular user, and #\nfor commands that should be executed as an administrator.
Lines that don’t start with $ or > character are typically showing\nthe output of the previous command.
Firstly, make sure to have downloaded and installed Node.js.\nSee this guide for further install information.
\nNow, create an empty project folder called projects, then navigate into it.\nThe project folder can be named based on the user's current project title, but\nthis example will use projects as the project folder.
Linux and Mac:
\n$ mkdir ~/projects\n$ cd ~/projects\nWindows CMD:
\n> mkdir %USERPROFILE%\\projects\n> cd %USERPROFILE%\\projects\nWindows PowerShell:
\n> mkdir $env:USERPROFILE\\projects\n> cd $env:USERPROFILE\\projects\nNext, create a new source file in the projects\nfolder and call it hello-world.js.
In Node.js it is considered good style to use\nhyphens (-) or underscores (_) to separate\nmultiple words in filenames.
Open hello-world.js in any preferred text editor and\npaste in the following content:
const http = require('http');\n\nconst hostname = '127.0.0.1';\nconst port = 3000;\n\nconst server = http.createServer((req, res) => {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/plain');\n res.end('Hello, World!\\n');\n});\n\nserver.listen(port, hostname, () => {\n console.log(`Server running at http://${hostname}:${port}/`);\n});\nSave the file, go back to the terminal window enter the following command:
\n$ node hello-world.js\nAn output like this should appear in the terminal to indicate Node.js\nserver is running:
\nServer running at http://127.0.0.1:3000/\nNow, open any preferred web browser and visit http://127.0.0.1:3000.
If the browser displays the string Hello, World!, that indicates\nthe server is working.
Many of the examples in the documentation can be run similarly.
" }, { "textRaw": "C++ Addons", "name": "C++ Addons", "introduced_in": "v0.10.0", "type": "misc", "desc": "Node.js Addons are dynamically-linked shared objects, written in C++, that\ncan be loaded into Node.js using the require() function, and used\njust as if they were an ordinary Node.js module. They are used primarily to\nprovide an interface between JavaScript running in Node.js and C/C++ libraries.
At the moment, the method for implementing Addons is rather complicated,\ninvolving knowledge of several components and APIs:
\nV8: the C++ library Node.js currently uses to provide the\nJavaScript implementation. V8 provides the mechanisms for creating objects,\ncalling functions, etc. V8's API is documented mostly in the\nv8.h header file (deps/v8/include/v8.h in the Node.js source\ntree), which is also available online.
libuv: The C library that implements the Node.js event loop, its worker\nthreads and all of the asynchronous behaviors of the platform. It also\nserves as a cross-platform abstraction library, giving easy, POSIX-like\naccess across all major operating systems to many common system tasks, such\nas interacting with the filesystem, sockets, timers, and system events. libuv\nalso provides a pthreads-like threading abstraction that may be used to\npower more sophisticated asynchronous Addons that need to move beyond the\nstandard event loop. Addon authors are encouraged to think about how to\navoid blocking the event loop with I/O or other time-intensive tasks by\noff-loading work via libuv to non-blocking system operations, worker threads\nor a custom use of libuv's threads.
\nInternal Node.js libraries. Node.js itself exports a number of C++ APIs\nthat Addons can use — the most important of which is the\nnode::ObjectWrap class.
Node.js includes a number of other statically linked libraries including\nOpenSSL. These other libraries are located in the deps/ directory in the\nNode.js source tree. Only the libuv, OpenSSL, V8 and zlib symbols are\npurposefully re-exported by Node.js and may be used to various extents by\nAddons.\nSee Linking to Node.js' own dependencies for additional information.
All of the following examples are available for download and may\nbe used as the starting-point for an Addon.
", "miscs": [ { "textRaw": "Hello world", "name": "hello_world", "desc": "This \"Hello world\" example is a simple Addon, written in C++, that is the\nequivalent of the following JavaScript code:
\nmodule.exports.hello = () => 'world';\nFirst, create the file hello.cc:
// hello.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid Method(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(\n isolate, \"world\", NewStringType::kNormal).ToLocalChecked());\n}\n\nvoid Initialize(Local<Object> exports) {\n NODE_SET_METHOD(exports, \"hello\", Method);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)\n\n} // namespace demo\nNote that all Node.js Addons must export an initialization function following\nthe pattern:
\nvoid Initialize(Local<Object> exports);\nNODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)\nThere is no semi-colon after NODE_MODULE as it's not a function (see\nnode.h).
The module_name must match the filename of the final binary (excluding\nthe .node suffix).
In the hello.cc example, then, the initialization function is Initialize\nand the addon module name is addon.
When building addons with node-gyp, using the macro NODE_GYP_MODULE_NAME as\nthe first parameter of NODE_MODULE() will ensure that the name of the final\nbinary will be passed to NODE_MODULE().
There are environments in which Node.js addons may need to be loaded multiple\ntimes in multiple contexts. For example, the Electron runtime runs multiple\ninstances of Node.js in a single process. Each instance will have its own\nrequire() cache, and thus each instance will need a native addon to behave\ncorrectly when loaded via require(). From the addon's perspective, this means\nthat it must support multiple initializations.
A context-aware addon can be constructed by using the macro\nNODE_MODULE_INITIALIZER, which expands to the name of a function which Node.js\nwill expect to find when it loads an addon. An addon can thus be initialized as\nin the following example:
using namespace v8;\n\nextern \"C\" NODE_MODULE_EXPORT void\nNODE_MODULE_INITIALIZER(Local<Object> exports,\n Local<Value> module,\n Local<Context> context) {\n /* Perform addon initialization steps here. */\n}\nAnother option is to use the macro NODE_MODULE_INIT(), which will also\nconstruct a context-aware addon. Unlike NODE_MODULE(), which is used to\nconstruct an addon around a given addon initializer function,\nNODE_MODULE_INIT() serves as the declaration of such an initializer to be\nfollowed by a function body.
The following three variables may be used inside the function body following an\ninvocation of NODE_MODULE_INIT():
Local<Object> exports,Local<Value> module, andLocal<Context> contextThe choice to build a context-aware addon carries with it the responsibility of\ncarefully managing global static data. Since the addon may be loaded multiple\ntimes, potentially even from different threads, any global static data stored\nin the addon must be properly protected, and must not contain any persistent\nreferences to JavaScript objects. The reason for this is that JavaScript\nobjects are only valid in one context, and will likely cause a crash when\naccessed from the wrong context or from a different thread than the one on which\nthey were created.
\nThe context-aware addon can be structured to avoid global static data by\nperforming the following steps:
\nv8::Persistent<v8::Object> which will hold a weak\nreference to the addon's exports object. The callback associated with the weak\nreference will then destroy the instance of the class.v8::Persistent<v8::Object> is set to the exports object.v8::External, andv8::External to all methods exposed to JavaScript by passing it\nto the v8::FunctionTemplate constructor which creates the native-backed\nJavaScript functions. The v8::FunctionTemplate constructor's third parameter\naccepts the v8::External.This will ensure that the per-addon-instance data reaches each binding that can\nbe called from JavaScript. The per-addon-instance data must also be passed into\nany asynchronous callbacks the addon may create.
\nThe following example illustrates the implementation of a context-aware addon:
\n#include <node.h>\n\nusing namespace v8;\n\nclass AddonData {\n public:\n AddonData(Isolate* isolate, Local<Object> exports):\n call_count(0) {\n // Link the existence of this object instance to the existence of exports.\n exports_.Reset(isolate, exports);\n exports_.SetWeak(this, DeleteMe, WeakCallbackType::kParameter);\n }\n\n ~AddonData() {\n if (!exports_.IsEmpty()) {\n // Reset the reference to avoid leaking data.\n exports_.ClearWeak();\n exports_.Reset();\n }\n }\n\n // Per-addon data.\n int call_count;\n\n private:\n // Method to call when \"exports\" is about to be garbage-collected.\n static void DeleteMe(const WeakCallbackInfo<AddonData>& info) {\n delete info.GetParameter();\n }\n\n // Weak handle to the \"exports\" object. An instance of this class will be\n // destroyed along with the exports object to which it is weakly bound.\n v8::Persistent<v8::Object> exports_;\n};\n\nstatic void Method(const v8::FunctionCallbackInfo<v8::Value>& info) {\n // Retrieve the per-addon-instance data.\n AddonData* data =\n reinterpret_cast<AddonData*>(info.Data().As<External>()->Value());\n data->call_count++;\n info.GetReturnValue().Set((double)data->call_count);\n}\n\n// Initialize this addon to be context-aware.\nNODE_MODULE_INIT(/* exports, module, context */) {\n Isolate* isolate = context->GetIsolate();\n\n // Create a new instance of AddonData for this instance of the addon.\n AddonData* data = new AddonData(isolate, exports);\n // Wrap the data in a v8::External so we can pass it to the method we expose.\n Local<External> external = External::New(isolate, data);\n\n // Expose the method \"Method\" to JavaScript, and make sure it receives the\n // per-addon-instance data we created above by passing `external` as the\n // third parameter to the FunctionTemplate constructor.\n exports->Set(context,\n String::NewFromUtf8(isolate, \"method\", NewStringType::kNormal)\n .ToLocalChecked(),\n FunctionTemplate::New(isolate, Method, external)\n ->GetFunction(context).ToLocalChecked()).FromJust();\n}\nOnce the source code has been written, it must be compiled into the binary\naddon.node file. To do so, create a file called binding.gyp in the\ntop-level of the project describing the build configuration of the module\nusing a JSON-like format. This file is used by node-gyp — a tool written\nspecifically to compile Node.js Addons.
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [ \"hello.cc\" ]\n }\n ]\n}\nA version of the node-gyp utility is bundled and distributed with\nNode.js as part of npm. This version is not made directly available for\ndevelopers to use and is intended only to support the ability to use the\nnpm install command to compile and install Addons. Developers who wish to\nuse node-gyp directly can install it using the command\nnpm install -g node-gyp. See the node-gyp installation instructions for\nmore information, including platform-specific requirements.
Once the binding.gyp file has been created, use node-gyp configure to\ngenerate the appropriate project build files for the current platform. This\nwill generate either a Makefile (on Unix platforms) or a vcxproj file\n(on Windows) in the build/ directory.
Next, invoke the node-gyp build command to generate the compiled addon.node\nfile. This will be put into the build/Release/ directory.
When using npm install to install a Node.js Addon, npm uses its own bundled\nversion of node-gyp to perform this same set of actions, generating a\ncompiled version of the Addon for the user's platform on demand.
Once built, the binary Addon can be used from within Node.js by pointing\nrequire() to the built addon.node module:
// hello.js\nconst addon = require('./build/Release/addon');\n\nconsole.log(addon.hello());\n// Prints: 'world'\nPlease see the examples below for further information or\nhttps://github.com/arturadib/node-qt for an example in production.
\nBecause the exact path to the compiled Addon binary can vary depending on how\nit is compiled (i.e. sometimes it may be in ./build/Debug/), Addons can use\nthe bindings package to load the compiled module.
Note that while the bindings package implementation is more sophisticated\nin how it locates Addon modules, it is essentially using a try-catch pattern\nsimilar to:
try {\n return require('./build/Release/addon.node');\n} catch (err) {\n return require('./build/Debug/addon.node');\n}\nNode.js uses a number of statically linked libraries such as V8, libuv and\nOpenSSL. All Addons are required to link to V8 and may link to any of the\nother dependencies as well. Typically, this is as simple as including\nthe appropriate #include <...> statements (e.g. #include <v8.h>) and\nnode-gyp will locate the appropriate headers automatically. However, there\nare a few caveats to be aware of:
When node-gyp runs, it will detect the specific release version of Node.js\nand download either the full source tarball or just the headers. If the full\nsource is downloaded, Addons will have complete access to the full set of\nNode.js dependencies. However, if only the Node.js headers are downloaded, then\nonly the symbols exported by Node.js will be available.
node-gyp can be run using the --nodedir flag pointing at a local Node.js\nsource image. Using this option, the Addon will have access to the full set of\ndependencies.
The filename extension of the compiled Addon binary is .node (as opposed\nto .dll or .so). The require() function is written to look for\nfiles with the .node file extension and initialize those as dynamically-linked\nlibraries.
When calling require(), the .node extension can usually be\nomitted and Node.js will still find and initialize the Addon. One caveat,\nhowever, is that Node.js will first attempt to locate and load modules or\nJavaScript files that happen to share the same base name. For instance, if\nthere is a file addon.js in the same directory as the binary addon.node,\nthen require('addon') will give precedence to the addon.js file\nand load it instead.
Each of the examples illustrated in this document make direct use of the\nNode.js and V8 APIs for implementing Addons. It is important to understand\nthat the V8 API can, and has, changed dramatically from one V8 release to the\nnext (and one major Node.js release to the next). With each change, Addons may\nneed to be updated and recompiled in order to continue functioning. The Node.js\nrelease schedule is designed to minimize the frequency and impact of such\nchanges but there is little that Node.js can do currently to ensure stability\nof the V8 APIs.
\nThe Native Abstractions for Node.js (or nan) provide a set of tools that\nAddon developers are recommended to use to keep compatibility between past and\nfuture releases of V8 and Node.js. See the nan examples for an\nillustration of how it can be used.
N-API is an API for building native Addons. It is independent from\nthe underlying JavaScript runtime (e.g. V8) and is maintained as part of\nNode.js itself. This API will be Application Binary Interface (ABI) stable\nacross versions of Node.js. It is intended to insulate Addons from\nchanges in the underlying JavaScript engine and allow modules\ncompiled for one version to run on later versions of Node.js without\nrecompilation. Addons are built/packaged with the same approach/tools\noutlined in this document (node-gyp, etc.). The only difference is the\nset of APIs that are used by the native code. Instead of using the V8\nor Native Abstractions for Node.js APIs, the functions available\nin the N-API are used.
\nCreating and maintaining an addon that benefits from the ABI stability\nprovided by N-API carries with it certain\nimplementation considerations.
\nTo use N-API in the above \"Hello world\" example, replace the content of\nhello.cc with the following. All other instructions remain the same.
// hello.cc using N-API\n#include <node_api.h>\n\nnamespace demo {\n\nnapi_value Method(napi_env env, napi_callback_info args) {\n napi_value greeting;\n napi_status status;\n\n status = napi_create_string_utf8(env, \"world\", NAPI_AUTO_LENGTH, &greeting);\n if (status != napi_ok) return nullptr;\n return greeting;\n}\n\nnapi_value init(napi_env env, napi_value exports) {\n napi_status status;\n napi_value fn;\n\n status = napi_create_function(env, nullptr, 0, Method, nullptr, &fn);\n if (status != napi_ok) return nullptr;\n\n status = napi_set_named_property(env, exports, \"hello\", fn);\n if (status != napi_ok) return nullptr;\n return exports;\n}\n\nNAPI_MODULE(NODE_GYP_MODULE_NAME, init)\n\n} // namespace demo\nThe functions available and how to use them are documented in the\nsection titled C/C++ Addons - N-API.
", "type": "misc", "displayName": "N-API" }, { "textRaw": "Addon examples", "name": "addon_examples", "desc": "Following are some example Addons intended to help developers get started. The\nexamples make use of the V8 APIs. Refer to the online V8 reference\nfor help with the various V8 calls, and V8's Embedder's Guide for an\nexplanation of several concepts used such as handles, scopes, function\ntemplates, etc.
\nEach of these examples using the following binding.gyp file:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [ \"addon.cc\" ]\n }\n ]\n}\nIn cases where there is more than one .cc file, simply add the additional\nfilename to the sources array:
\"sources\": [\"addon.cc\", \"myexample.cc\"]\nOnce the binding.gyp file is ready, the example Addons can be configured and\nbuilt using node-gyp:
$ node-gyp configure build\nAddons will typically expose objects and functions that can be accessed from\nJavaScript running within Node.js. When functions are invoked from JavaScript,\nthe input arguments and return value must be mapped to and from the C/C++\ncode.
\nThe following example illustrates how to read function arguments passed from\nJavaScript and how to return a result:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Exception;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\n// This is the implementation of the \"add\" method\n// Input arguments are passed using the\n// const FunctionCallbackInfo<Value>& args struct\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n // Check the number of arguments passed.\n if (args.Length() < 2) {\n // Throw an Error that is passed back to JavaScript\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate,\n \"Wrong number of arguments\",\n NewStringType::kNormal).ToLocalChecked()));\n return;\n }\n\n // Check the argument types\n if (!args[0]->IsNumber() || !args[1]->IsNumber()) {\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate,\n \"Wrong arguments\",\n NewStringType::kNormal).ToLocalChecked()));\n return;\n }\n\n // Perform the operation\n double value =\n args[0].As<Number>()->Value() + args[1].As<Number>()->Value();\n Local<Number> num = Number::New(isolate, value);\n\n // Set the return value (using the passed in\n // FunctionCallbackInfo<Value>&)\n args.GetReturnValue().Set(num);\n}\n\nvoid Init(Local<Object> exports) {\n NODE_SET_METHOD(exports, \"add\", Add);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\nOnce compiled, the example Addon can be required and used from within Node.js:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconsole.log('This should be eight:', addon.add(3, 5));\nIt is common practice within Addons to pass JavaScript functions to a C++\nfunction and execute them from there. The following example illustrates how\nto invoke such callbacks:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Null;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid RunCallback(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n Local<Function> cb = Local<Function>::Cast(args[0]);\n const unsigned argc = 1;\n Local<Value> argv[argc] = {\n String::NewFromUtf8(isolate,\n \"hello world\",\n NewStringType::kNormal).ToLocalChecked() };\n cb->Call(context, Null(isolate), argc, argv).ToLocalChecked();\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", RunCallback);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\nNote that this example uses a two-argument form of Init() that receives\nthe full module object as the second argument. This allows the Addon\nto completely overwrite exports with a single function instead of\nadding the function as a property of exports.
To test it, run the following JavaScript:
\n// test.js\nconst addon = require('./build/Release/addon');\n\naddon((msg) => {\n console.log(msg);\n// Prints: 'hello world'\n});\nNote that, in this example, the callback function is invoked synchronously.
", "type": "module", "displayName": "Callbacks" }, { "textRaw": "Object factory", "name": "object_factory", "desc": "Addons can create and return new objects from within a C++ function as\nillustrated in the following example. An object is created and returned with a\nproperty msg that echoes the string passed to createObject():
// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n Local<Object> obj = Object::New(isolate);\n obj->Set(context,\n String::NewFromUtf8(isolate,\n \"msg\",\n NewStringType::kNormal).ToLocalChecked(),\n args[0]->ToString(context).ToLocalChecked())\n .FromJust();\n\n args.GetReturnValue().Set(obj);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", CreateObject);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\nTo test it in JavaScript:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj1 = addon('hello');\nconst obj2 = addon('world');\nconsole.log(obj1.msg, obj2.msg);\n// Prints: 'hello world'\nAnother common scenario is creating JavaScript functions that wrap C++\nfunctions and returning those back to JavaScript:
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid MyFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(\n isolate, \"hello world\", NewStringType::kNormal).ToLocalChecked());\n}\n\nvoid CreateFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n Local<Context> context = isolate->GetCurrentContext();\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, MyFunction);\n Local<Function> fn = tpl->GetFunction(context).ToLocalChecked();\n\n // omit this to make it anonymous\n fn->SetName(String::NewFromUtf8(\n isolate, \"theFunction\", NewStringType::kNormal).ToLocalChecked());\n\n args.GetReturnValue().Set(fn);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, \"exports\", CreateFunction);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, Init)\n\n} // namespace demo\nTo test:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst fn = addon();\nconsole.log(fn());\n// Prints: 'hello world'\nIt is also possible to wrap C++ objects/classes in a way that allows new\ninstances to be created using the JavaScript new operator:
// addon.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Local;\nusing v8::Object;\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\nThen, in myobject.h, the wrapper class inherits from node::ObjectWrap:
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Local<v8::Object> exports);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif\nIn myobject.cc, implement the various methods that are to be exposed.\nBelow, the method plusOne() is exposed by adding it to the constructor's\nprototype:
// myobject.cc\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Local<Object> exports) {\n Isolate* isolate = exports->GetIsolate();\n\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, \"plusOne\", PlusOne);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\n exports->Set(context, String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked(),\n tpl->GetFunction(context).ToLocalChecked()).FromJust();\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> result =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(result);\n }\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo\nTo build this example, the myobject.cc file must be added to the\nbinding.gyp:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [\n \"addon.cc\",\n \"myobject.cc\"\n ]\n }\n ]\n}\nTest it with:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj = new addon.MyObject(10);\nconsole.log(obj.plusOne());\n// Prints: 11\nconsole.log(obj.plusOne());\n// Prints: 12\nconsole.log(obj.plusOne());\n// Prints: 13\nThe destructor for a wrapper object will run when the object is\ngarbage-collected. For destructor testing, there are command-line flags that\ncan be used to make it possible to force garbage collection. These flags are\nprovided by the underlying V8 JavaScript engine. They are subject to change\nor removal at any time. They are not documented by Node.js or V8, and they\nshould never be used outside of testing.
", "type": "module", "displayName": "Wrapping C++ objects" }, { "textRaw": "Factory of wrapped objects", "name": "factory_of_wrapped_objects", "desc": "Alternatively, it is possible to use a factory pattern to avoid explicitly\ncreating object instances using the JavaScript new operator:
const obj = addon.createObject();\n// instead of:\n// const obj = new addon.Object();\nFirst, the createObject() method is implemented in addon.cc:
// addon.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid InitAll(Local<Object> exports, Local<Object> module) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(module, \"exports\", CreateObject);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\nIn myobject.h, the static method NewInstance() is added to handle\ninstantiating the object. This method takes the place of using new in\nJavaScript:
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif\nThe implementation in myobject.cc is similar to the previous example:
// myobject.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, \"plusOne\", PlusOne);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(instance);\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Context> context = isolate->GetCurrentContext();\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n\n args.GetReturnValue().Set(instance);\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo\nOnce again, to build this example, the myobject.cc file must be added to the\nbinding.gyp:
{\n \"targets\": [\n {\n \"target_name\": \"addon\",\n \"sources\": [\n \"addon.cc\",\n \"myobject.cc\"\n ]\n }\n ]\n}\nTest it with:
\n// test.js\nconst createObject = require('./build/Release/addon');\n\nconst obj = createObject(10);\nconsole.log(obj.plusOne());\n// Prints: 11\nconsole.log(obj.plusOne());\n// Prints: 12\nconsole.log(obj.plusOne());\n// Prints: 13\n\nconst obj2 = createObject(20);\nconsole.log(obj2.plusOne());\n// Prints: 21\nconsole.log(obj2.plusOne());\n// Prints: 22\nconsole.log(obj2.plusOne());\n// Prints: 23\nIn addition to wrapping and returning C++ objects, it is possible to pass\nwrapped objects around by unwrapping them with the Node.js helper function\nnode::ObjectWrap::Unwrap. The following examples shows a function add()\nthat can take two MyObject objects as input arguments:
// addon.cc\n#include <node.h>\n#include <node_object_wrap.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n MyObject* obj1 = node::ObjectWrap::Unwrap<MyObject>(\n args[0]->ToObject(context).ToLocalChecked());\n MyObject* obj2 = node::ObjectWrap::Unwrap<MyObject>(\n args[1]->ToObject(context).ToLocalChecked());\n\n double sum = obj1->value() + obj2->value();\n args.GetReturnValue().Set(Number::New(isolate, sum));\n}\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(exports, \"createObject\", CreateObject);\n NODE_SET_METHOD(exports, \"add\", Add);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, InitAll)\n\n} // namespace demo\nIn myobject.h, a new public method is added to allow access to private values\nafter unwrapping the object.
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n inline double value() const { return value_; }\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif\nThe implementation of myobject.cc is similar to before:
// myobject.cc\n#include <node.h>\n#include \"myobject.h\"\n\nnamespace demo {\n\nusing v8::Context;\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::NewStringType;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(\n isolate, \"MyObject\", NewStringType::kNormal).ToLocalChecked());\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n Local<Context> context = isolate->GetCurrentContext();\n constructor.Reset(isolate, tpl->GetFunction(context).ToLocalChecked());\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Context> context = isolate->GetCurrentContext();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ?\n 0 : args[0]->NumberValue(context).FromMaybe(0);\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n args.GetReturnValue().Set(instance);\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Context> context = isolate->GetCurrentContext();\n Local<Object> instance =\n cons->NewInstance(context, argc, argv).ToLocalChecked();\n\n args.GetReturnValue().Set(instance);\n}\n\n} // namespace demo\nTest it with:
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconst obj1 = addon.createObject(10);\nconst obj2 = addon.createObject(20);\nconst result = addon.add(obj1, obj2);\n\nconsole.log(result);\n// Prints: 30\nAn AtExit hook is a function that is invoked after the Node.js event loop\nhas ended but before the JavaScript VM is terminated and Node.js shuts down.\nAtExit hooks are registered using the node::AtExit API.
callback <void (*)(void*)>\nA pointer to the function to call at exit.args <void*>\nA pointer to pass to the callback at exit.Registers exit hooks that run after the event loop has ended but before the VM\nis killed.
\nAtExit takes two parameters: a pointer to a callback function to run at exit,\nand a pointer to untyped context data to be passed to that callback.
Callbacks are run in last-in first-out order.
\nThe following addon.cc implements AtExit:
// addon.cc\n#include <assert.h>\n#include <stdlib.h>\n#include <node.h>\n\nnamespace demo {\n\nusing node::AtExit;\nusing v8::HandleScope;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\n\nstatic char cookie[] = \"yum yum\";\nstatic int at_exit_cb1_called = 0;\nstatic int at_exit_cb2_called = 0;\n\nstatic void at_exit_cb1(void* arg) {\n Isolate* isolate = static_cast<Isolate*>(arg);\n HandleScope scope(isolate);\n Local<Object> obj = Object::New(isolate);\n assert(!obj.IsEmpty()); // assert VM is still alive\n assert(obj->IsObject());\n at_exit_cb1_called++;\n}\n\nstatic void at_exit_cb2(void* arg) {\n assert(arg == static_cast<void*>(cookie));\n at_exit_cb2_called++;\n}\n\nstatic void sanity_check(void*) {\n assert(at_exit_cb1_called == 1);\n assert(at_exit_cb2_called == 2);\n}\n\nvoid init(Local<Object> exports) {\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb1, exports->GetIsolate());\n AtExit(sanity_check);\n}\n\nNODE_MODULE(NODE_GYP_MODULE_NAME, init)\n\n} // namespace demo\nTest in JavaScript by running:
\n// test.js\nrequire('./build/Release/addon');\nN-API (pronounced N as in the letter, followed by API)\nis an API for building native Addons. It is independent from\nthe underlying JavaScript runtime (ex V8) and is maintained as part of\nNode.js itself. This API will be Application Binary Interface (ABI) stable\nacross versions of Node.js. It is intended to insulate Addons from\nchanges in the underlying JavaScript engine and allow modules\ncompiled for one major version to run on later major versions of Node.js without\nrecompilation. The ABI Stability guide provides a more in-depth explanation.
\nAddons are built/packaged with the same approach/tools\noutlined in the section titled C++ Addons.\nThe only difference is the set of APIs that are used by the native code.\nInstead of using the V8 or Native Abstractions for Node.js APIs,\nthe functions available in the N-API are used.
\nAPIs exposed by N-API are generally used to create and manipulate\nJavaScript values. Concepts and operations generally map to ideas specified\nin the ECMA262 Language Specification. The APIs have the following\nproperties:
\nnapi_status. This\nstatus indicates whether the API call succeeded or failed.napi_value.napi_get_last_error_info. More information can be found in the error\nhandling section Error Handling.The N-API is a C API that ensures ABI stability across Node.js versions\nand different compiler levels. A C++ API can be easier to use.\nTo support using C++, the project maintains a\nC++ wrapper module called\nnode-addon-api.\nThis wrapper provides an inlineable C++ API. Binaries built\nwith node-addon-api will depend on the symbols for the N-API C-based\nfunctions exported by Node.js. node-addon-api is a more\nefficient way to write code that calls N-API. Take, for example, the\nfollowing node-addon-api code. The first section shows the\nnode-addon-api code and the second section shows what actually gets\nused in the addon.
Object obj = Object::New(env);\nobj[\"foo\"] = String::New(env, \"bar\");\nnapi_status status;\nnapi_value object, string;\nstatus = napi_create_object(env, &object);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\n\nstatus = napi_create_string_utf8(env, \"bar\", NAPI_AUTO_LENGTH, &string);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\n\nstatus = napi_set_named_property(env, object, \"foo\", string);\nif (status != napi_ok) {\n napi_throw_error(env, ...);\n return;\n}\nThe end result is that the addon only uses the exported C APIs. As a result,\nit still gets the benefits of the ABI stability provided by the C API.
\nWhen using node-addon-api instead of the C APIs, start with the API\ndocs\nfor node-addon-api.
Although N-API provides an ABI stability guarantee, other parts of Node.js do\nnot, and any external libraries used from the addon may not. In particular,\nnone of the following APIs provide an ABI stability guarantee across major\nversions:
\nthe Node.js C++ APIs available via any of
\n#include <node.h>\n#include <node_buffer.h>\n#include <node_version.h>\n#include <node_object_wrap.h>\nthe libuv APIs which are also included with Node.js and available via
\n#include <uv.h>\nthe V8 API available via
\n#include <v8.h>\nThus, for an addon to remain ABI-compatible across Node.js major versions, it\nmust make use exclusively of N-API by restricting itself to using
\n#include <node_api.h>\nand by checking, for all external libraries that it uses, that the external\nlibrary makes ABI stability guarantees similar to N-API.
", "type": "misc", "displayName": "Implications of ABI Stability" }, { "textRaw": "Usage", "name": "usage", "desc": "In order to use the N-API functions, include the file\nnode_api.h\nwhich is located in the src directory in the node development tree:
#include <node_api.h>\nThis will opt into the default NAPI_VERSION for the given release of Node.js.\nIn order to ensure compatibility with specific versions of N-API, the version\ncan be specified explicitly when including the header:
#define NAPI_VERSION 3\n#include <node_api.h>\nThis restricts the N-API surface to just the functionality that was available in\nthe specified (and earlier) versions.
\nSome of the N-API surface is considered experimental and requires explicit\nopt-in to access those APIs:
\n#define NAPI_EXPERIMENTAL\n#include <node_api.h>\nIn this case the entire API surface, including any experimental APIs, will be\navailable to the module code.
", "type": "misc", "displayName": "Usage" }, { "textRaw": "N-API Version Matrix", "name": "n-api_version_matrix", "desc": "| \n | 1 | \n2 | \n3 | \n4 | \n5 | \n
|---|---|---|---|---|---|
| v6.x | \n\n | \n | v6.14.2* | \n\n | \n |
| v8.x | \nv8.0.0* | \nv8.10.0* | \nv8.11.2 | \n\n | \n |
| v9.x | \nv9.0.0* | \nv9.3.0* | \nv9.11.0* | \n\n | \n |
| v10.x | \n\n | \n | v10.0.0 | \nv10.16.0 | \nv10.17.0 | \n
| v11.x | \n\n | \n | v11.0.0 | \nv11.8.0 | \n\n |
| v12.x | \n\n | \n | \n | v12.0.0 | \n\n |
| v13.x | \n\n | \n | \n | \n | \n |
* Indicates that the N-API version was released as experimental
", "type": "misc", "displayName": "N-API Version Matrix" }, { "textRaw": "Basic N-API Data Types", "name": "basic_n-api_data_types", "desc": "N-API exposes the following fundamental datatypes as abstractions that are\nconsumed by the various APIs. These APIs should be treated as opaque,\nintrospectable only with other N-API calls.
", "modules": [ { "textRaw": "napi_status", "name": "napi_status", "desc": "Integral status code indicating the success or failure of a N-API call.\nCurrently, the following status codes are supported.
\ntypedef enum {\n napi_ok,\n napi_invalid_arg,\n napi_object_expected,\n napi_string_expected,\n napi_name_expected,\n napi_function_expected,\n napi_number_expected,\n napi_boolean_expected,\n napi_array_expected,\n napi_generic_failure,\n napi_pending_exception,\n napi_cancelled,\n napi_escape_called_twice,\n napi_handle_scope_mismatch,\n napi_callback_scope_mismatch,\n napi_queue_full,\n napi_closing,\n napi_bigint_expected,\n napi_date_expected,\n} napi_status;\nIf additional information is required upon an API returning a failed status,\nit can be obtained by calling napi_get_last_error_info.
typedef struct {\n const char* error_message;\n void* engine_reserved;\n uint32_t engine_error_code;\n napi_status error_code;\n} napi_extended_error_info;\nerror_message: UTF8-encoded string containing a VM-neutral description of\nthe error.engine_reserved: Reserved for VM-specific error details. This is currently\nnot implemented for any VM.engine_error_code: VM-specific error code. This is currently\nnot implemented for any VM.error_code: The N-API status code that originated with the last error.See the Error Handling section for additional information.
", "type": "module", "displayName": "napi_extended_error_info" }, { "textRaw": "napi_env", "name": "napi_env", "desc": "napi_env is used to represent a context that the underlying N-API\nimplementation can use to persist VM-specific state. This structure is passed\nto native functions when they're invoked, and it must be passed back when\nmaking N-API calls. Specifically, the same napi_env that was passed in when\nthe initial native function was called must be passed to any subsequent\nnested N-API calls. Caching the napi_env for the purpose of general reuse is\nnot allowed.
This is an opaque pointer that is used to represent a JavaScript value.
", "type": "module", "displayName": "napi_value" }, { "textRaw": "napi_threadsafe_function", "name": "napi_threadsafe_function", "stability": 2, "stabilityText": "Stable", "desc": "This is an opaque pointer that represents a JavaScript function which can be\ncalled asynchronously from multiple threads via\nnapi_call_threadsafe_function().
A value to be given to napi_release_threadsafe_function() to indicate whether\nthe thread-safe function is to be closed immediately (napi_tsfn_abort) or\nmerely released (napi_tsfn_release) and thus available for subsequent use via\nnapi_acquire_threadsafe_function() and napi_call_threadsafe_function().
typedef enum {\n napi_tsfn_release,\n napi_tsfn_abort\n} napi_threadsafe_function_release_mode;\nA value to be given to napi_call_threadsafe_function() to indicate whether\nthe call should block whenever the queue associated with the thread-safe\nfunction is full.
typedef enum {\n napi_tsfn_nonblocking,\n napi_tsfn_blocking\n} napi_threadsafe_function_call_mode;\nThis is an abstraction used to control and modify the lifetime of objects\ncreated within a particular scope. In general, N-API values are created within\nthe context of a handle scope. When a native method is called from\nJavaScript, a default handle scope will exist. If the user does not explicitly\ncreate a new handle scope, N-API values will be created in the default handle\nscope. For any invocations of code outside the execution of a native method\n(for instance, during a libuv callback invocation), the module is required to\ncreate a scope before invoking any functions that can result in the creation\nof JavaScript values.
\nHandle scopes are created using napi_open_handle_scope and are destroyed\nusing napi_close_handle_scope. Closing the scope can indicate to the GC\nthat all napi_values created during the lifetime of the handle scope are no\nlonger referenced from the current stack frame.
For more details, review the Object Lifetime Management.
", "type": "module", "displayName": "napi_handle_scope" }, { "textRaw": "napi_escapable_handle_scope", "name": "napi_escapable_handle_scope", "desc": "Escapable handle scopes are a special type of handle scope to return values\ncreated within a particular handle scope to a parent scope.
", "type": "module", "displayName": "napi_escapable_handle_scope" }, { "textRaw": "napi_ref", "name": "napi_ref", "desc": "This is the abstraction to use to reference a napi_value. This allows for\nusers to manage the lifetimes of JavaScript values, including defining their\nminimum lifetimes explicitly.
For more details, review the Object Lifetime Management.
", "type": "module", "displayName": "napi_ref" } ], "type": "module", "displayName": "N-API Memory Management types" }, { "textRaw": "N-API Callback types", "name": "n-api_callback_types", "modules": [ { "textRaw": "napi_callback_info", "name": "napi_callback_info", "desc": "Opaque datatype that is passed to a callback function. It can be used for\ngetting additional information about the context in which the callback was\ninvoked.
", "type": "module", "displayName": "napi_callback_info" }, { "textRaw": "napi_callback", "name": "napi_callback", "desc": "Function pointer type for user-provided native functions which are to be\nexposed to JavaScript via N-API. Callback functions should satisfy the\nfollowing signature:
\ntypedef napi_value (*napi_callback)(napi_env, napi_callback_info);\nFunction pointer type for add-on provided functions that allow the user to be\nnotified when externally-owned data is ready to be cleaned up because the\nobject with which it was associated with, has been garbage-collected. The user\nmust provide a function satisfying the following signature which would get\ncalled upon the object's collection. Currently, napi_finalize can be used for\nfinding out when objects that have external data are collected.
typedef void (*napi_finalize)(napi_env env,\n void* finalize_data,\n void* finalize_hint);\nFunction pointer used with functions that support asynchronous\noperations. Callback functions must statisfy the following signature:
\ntypedef void (*napi_async_execute_callback)(napi_env env, void* data);\nImplementations of this type of function should avoid making any N-API calls\nthat could result in the execution of JavaScript or interaction with\nJavaScript objects. Most often, any code that needs to make N-API\ncalls should be made in napi_async_complete_callback instead.
Function pointer used with functions that support asynchronous\noperations. Callback functions must statisfy the following signature:
\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\nFunction pointer used with asynchronous thread-safe function calls. The callback\nwill be called on the main thread. Its purpose is to use a data item arriving\nvia the queue from one of the secondary threads to construct the parameters\nnecessary for a call into JavaScript, usually via napi_call_function, and then\nmake the call into JavaScript.
The data arriving from the secondary thread via the queue is given in the data\nparameter and the JavaScript function to call is given in the js_callback\nparameter.
N-API sets up the environment prior to calling this callback, so it is\nsufficient to call the JavaScript function via napi_call_function rather than\nvia napi_make_callback.
Callback functions must satisfy the following signature:
\ntypedef void (*napi_threadsafe_function_call_js)(napi_env env,\n napi_value js_callback,\n void* context,\n void* data);\n[in] env: The environment to use for API calls, or NULL if the thread-safe\nfunction is being torn down and data may need to be freed.[in] js_callback: The JavaScript function to call, or NULL if the\nthread-safe function is being torn down and data may need to be freed. It may\nalso be NULL if the thread-safe function was created without js_callback.[in] context: The optional data with which the thread-safe function was\ncreated.[in] data: Data created by the secondary thread. It is the responsibility of\nthe callback to convert this native data to JavaScript values (with N-API\nfunctions) that can be passed as parameters when js_callback is invoked. This\npointer is managed entirely by the threads and this callback. Thus this callback\nshould free the data.N-API uses both return values and JavaScript exceptions for error handling.\nThe following sections explain the approach for each case.
", "modules": [ { "textRaw": "Return values", "name": "return_values", "desc": "All of the N-API functions share the same error handling pattern. The\nreturn type of all API functions is napi_status.
The return value will be napi_ok if the request was successful and\nno uncaught JavaScript exception was thrown. If an error occurred AND\nan exception was thrown, the napi_status value for the error\nwill be returned. If an exception was thrown, and no error occurred,\nnapi_pending_exception will be returned.
In cases where a return value other than napi_ok or\nnapi_pending_exception is returned, napi_is_exception_pending\nmust be called to check if an exception is pending.\nSee the section on exceptions for more details.
The full set of possible napi_status values is defined\nin napi_api_types.h.
The napi_status return value provides a VM-independent representation of\nthe error which occurred. In some cases it is useful to be able to get\nmore detailed information, including a string representing the error as well as\nVM (engine)-specific information.
In order to retrieve this information napi_get_last_error_info\nis provided which returns a napi_extended_error_info structure.\nThe format of the napi_extended_error_info structure is as follows:
typedef struct napi_extended_error_info {\n const char* error_message;\n void* engine_reserved;\n uint32_t engine_error_code;\n napi_status error_code;\n};\nerror_message: Textual representation of the error that occurred.engine_reserved: Opaque handle reserved for engine use only.engine_error_code: VM specific error code.error_code: n-api status code for the last error.napi_get_last_error_info returns the information for the last\nN-API call that was made.
Do not rely on the content or format of any of the extended information as it\nis not subject to SemVer and may change at any time. It is intended only for\nlogging purposes.
", "modules": [ { "textRaw": "napi_get_last_error_info", "name": "napi_get_last_error_info", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status\nnapi_get_last_error_info(napi_env env,\n const napi_extended_error_info** result);\n[in] env: The environment that the API is invoked under.[out] result: The napi_extended_error_info structure with more\ninformation about the error.Returns napi_ok if the API succeeded.
This API retrieves a napi_extended_error_info structure with information\nabout the last error that occurred.
The content of the napi_extended_error_info returned is only valid up until\nan n-api function is called on the same env.
Do not rely on the content or format of any of the extended information as it\nis not subject to SemVer and may change at any time. It is intended only for\nlogging purposes.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_get_last_error_info" } ], "type": "module", "displayName": "Return values" }, { "textRaw": "Exceptions", "name": "exceptions", "desc": "Any N-API function call may result in a pending JavaScript exception. This is\nobviously the case for any function that may cause the execution of\nJavaScript, but N-API specifies that an exception may be pending\non return from any of the API functions.
\nIf the napi_status returned by a function is napi_ok then no\nexception is pending and no additional action is required. If the\nnapi_status returned is anything other than napi_ok or\nnapi_pending_exception, in order to try to recover and continue\ninstead of simply returning immediately, napi_is_exception_pending\nmust be called in order to determine if an exception is pending or not.
In many cases when an N-API function is called and an exception is\nalready pending, the function will return immediately with a\nnapi_status of napi_pending_exception. However, this is not the case\nfor all functions. N-API allows a subset of the functions to be\ncalled to allow for some minimal cleanup before returning to JavaScript.\nIn that case, napi_status will reflect the status for the function. It\nwill not reflect previous pending exceptions. To avoid confusion, check\nthe error status after every function call.
When an exception is pending one of two approaches can be employed.
\nThe first approach is to do any appropriate cleanup and then return so that\nexecution will return to JavaScript. As part of the transition back to\nJavaScript the exception will be thrown at the point in the JavaScript\ncode where the native method was invoked. The behavior of most N-API calls\nis unspecified while an exception is pending, and many will simply return\nnapi_pending_exception, so it is important to do as little as possible\nand then return to JavaScript where the exception can be handled.
The second approach is to try to handle the exception. There will be cases\nwhere the native code can catch the exception, take the appropriate action,\nand then continue. This is only recommended in specific cases\nwhere it is known that the exception can be safely handled. In these\ncases napi_get_and_clear_last_exception can be used to get and\nclear the exception. On success, result will contain the handle to\nthe last JavaScript Object thrown. If it is determined, after\nretrieving the exception, the exception cannot be handled after all\nit can be re-thrown it with napi_throw where error is the\nJavaScript Error object to be thrown.
The following utility functions are also available in case native code\nneeds to throw an exception or determine if a napi_value is an instance\nof a JavaScript Error object: napi_throw_error,\nnapi_throw_type_error, napi_throw_range_error and\nnapi_is_error.
The following utility functions are also available in case native\ncode needs to create an Error object: napi_create_error,\nnapi_create_type_error, and napi_create_range_error,\nwhere result is the napi_value that refers to the newly created\nJavaScript Error object.
The Node.js project is adding error codes to all of the errors\ngenerated internally. The goal is for applications to use these\nerror codes for all error checking. The associated error messages\nwill remain, but will only be meant to be used for logging and\ndisplay with the expectation that the message can change without\nSemVer applying. In order to support this model with N-API, both\nin internal functionality and for module specific functionality\n(as its good practice), the throw_ and create_ functions\ntake an optional code parameter which is the string for the code\nto be added to the error object. If the optional parameter is NULL\nthen no code will be associated with the error. If a code is provided,\nthe name associated with the error is also updated to be:
originalName [code]\nwhere originalName is the original name associated with the error\nand code is the code that was provided. For example, if the code\nis 'ERR_ERROR_1' and a TypeError is being created the name will be:
TypeError [ERR_ERROR_1]\nNAPI_EXTERN napi_status napi_throw(napi_env env, napi_value error);\n[in] env: The environment that the API is invoked under.[in] error: The JavaScript value to be thrown.Returns napi_ok if the API succeeded.
This API throws the JavaScript value provided.
", "type": "module", "displayName": "napi_throw" }, { "textRaw": "napi_throw_error", "name": "napi_throw_error", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_throw_error(napi_env env,\n const char* code,\n const char* msg);\n[in] env: The environment that the API is invoked under.[in] code: Optional error code to be set on the error.[in] msg: C string representing the text to be associated with\nthe error.Returns napi_ok if the API succeeded.
This API throws a JavaScript Error with the text provided.
NAPI_EXTERN napi_status napi_throw_type_error(napi_env env,\n const char* code,\n const char* msg);\n[in] env: The environment that the API is invoked under.[in] code: Optional error code to be set on the error.[in] msg: C string representing the text to be associated with\nthe error.Returns napi_ok if the API succeeded.
This API throws a JavaScript TypeError with the text provided.
NAPI_EXTERN napi_status napi_throw_range_error(napi_env env,\n const char* code,\n const char* msg);\n[in] env: The environment that the API is invoked under.[in] code: Optional error code to be set on the error.[in] msg: C string representing the text to be associated with\nthe error.Returns napi_ok if the API succeeded.
This API throws a JavaScript RangeError with the text provided.
NAPI_EXTERN napi_status napi_is_error(napi_env env,\n napi_value value,\n bool* result);\n[in] env: The environment that the API is invoked under.[in] value: The napi_value to be checked.[out] result: Boolean value that is set to true if napi_value represents\nan error, false otherwise.Returns napi_ok if the API succeeded.
This API queries a napi_value to check if it represents an error object.
NAPI_EXTERN napi_status napi_create_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] code: Optional napi_value with the string for the error code to\nbe associated with the error.[in] msg: napi_value that references a JavaScript String to be\nused as the message for the Error.[out] result: napi_value representing the error created.Returns napi_ok if the API succeeded.
This API returns a JavaScript Error with the text provided.
NAPI_EXTERN napi_status napi_create_type_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] code: Optional napi_value with the string for the error code to\nbe associated with the error.[in] msg: napi_value that references a JavaScript String to be\nused as the message for the Error.[out] result: napi_value representing the error created.Returns napi_ok if the API succeeded.
This API returns a JavaScript TypeError with the text provided.
NAPI_EXTERN napi_status napi_create_range_error(napi_env env,\n napi_value code,\n napi_value msg,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] code: Optional napi_value with the string for the error code to\nbe associated with the error.[in] msg: napi_value that references a JavaScript String to be\nused as the message for the Error.[out] result: napi_value representing the error created.Returns napi_ok if the API succeeded.
This API returns a JavaScript RangeError with the text provided.
napi_status napi_get_and_clear_last_exception(napi_env env,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[out] result: The exception if one is pending, NULL otherwise.Returns napi_ok if the API succeeded.
This API returns true if an exception is pending.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_get_and_clear_last_exception" }, { "textRaw": "napi_is_exception_pending", "name": "napi_is_exception_pending", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_is_exception_pending(napi_env env, bool* result);\n[in] env: The environment that the API is invoked under.[out] result: Boolean value that is set to true if an exception is pending.Returns napi_ok if the API succeeded.
This API returns true if an exception is pending.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_is_exception_pending" }, { "textRaw": "napi_fatal_exception", "name": "napi_fatal_exception", "meta": { "added": [ "v9.10.0" ], "napiVersion": [ 3 ], "changes": [] }, "desc": "napi_status napi_fatal_exception(napi_env env, napi_value err);\n[in] env: The environment that the API is invoked under.[in] err: The error that is passed to 'uncaughtException'.Trigger an 'uncaughtException' in JavaScript. Useful if an async\ncallback throws an exception with no way to recover.
In the event of an unrecoverable error in a native module, a fatal error can be\nthrown to immediately terminate the process.
", "modules": [ { "textRaw": "napi_fatal_error", "name": "napi_fatal_error", "meta": { "added": [ "v8.2.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_NO_RETURN void napi_fatal_error(const char* location,\n size_t location_len,\n const char* message,\n size_t message_len);\n[in] location: Optional location at which the error occurred.[in] location_len: The length of the location in bytes, or\nNAPI_AUTO_LENGTH if it is null-terminated.[in] message: The message associated with the error.[in] message_len: The length of the message in bytes, or\nNAPI_AUTO_LENGTH if it is\nnull-terminated.The function call does not return, the process will be terminated.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_fatal_error" } ], "type": "module", "displayName": "Fatal Errors" } ], "type": "misc", "displayName": "Error Handling" }, { "textRaw": "Object Lifetime management", "name": "object_lifetime_management", "desc": "As N-API calls are made, handles to objects in the heap for the underlying\nVM may be returned as napi_values. These handles must hold the\nobjects 'live' until they are no longer required by the native code,\notherwise the objects could be collected before the native code was\nfinished using them.
As object handles are returned they are associated with a\n'scope'. The lifespan for the default scope is tied to the lifespan\nof the native method call. The result is that, by default, handles\nremain valid and the objects associated with these handles will be\nheld live for the lifespan of the native method call.
\nIn many cases, however, it is necessary that the handles remain valid for\neither a shorter or longer lifespan than that of the native method.\nThe sections which follow describe the N-API functions that can be used\nto change the handle lifespan from the default.
", "modules": [ { "textRaw": "Making handle lifespan shorter than that of the native method", "name": "making_handle_lifespan_shorter_than_that_of_the_native_method", "desc": "It is often necessary to make the lifespan of handles shorter than\nthe lifespan of a native method. For example, consider a native method\nthat has a loop which iterates through the elements in a large array:
\nfor (int i = 0; i < 1000000; i++) {\n napi_value result;\n napi_status status = napi_get_element(env, object, i, &result);\n if (status != napi_ok) {\n break;\n }\n // do something with element\n}\nThis would result in a large number of handles being created, consuming\nsubstantial resources. In addition, even though the native code could only\nuse the most recent handle, all of the associated objects would also be\nkept alive since they all share the same scope.
\nTo handle this case, N-API provides the ability to establish a new 'scope' to\nwhich newly created handles will be associated. Once those handles\nare no longer required, the scope can be 'closed' and any handles associated\nwith the scope are invalidated. The methods available to open/close scopes are\nnapi_open_handle_scope and napi_close_handle_scope.
N-API only supports a single nested hierarchy of scopes. There is only one\nactive scope at any time, and all new handles will be associated with that\nscope while it is active. Scopes must be closed in the reverse order from\nwhich they are opened. In addition, all scopes created within a native method\nmust be closed before returning from that method.
\nTaking the earlier example, adding calls to napi_open_handle_scope and\nnapi_close_handle_scope would ensure that at most a single handle\nis valid throughout the execution of the loop:
for (int i = 0; i < 1000000; i++) {\n napi_handle_scope scope;\n napi_status status = napi_open_handle_scope(env, &scope);\n if (status != napi_ok) {\n break;\n }\n napi_value result;\n status = napi_get_element(env, object, i, &result);\n if (status != napi_ok) {\n break;\n }\n // do something with element\n status = napi_close_handle_scope(env, scope);\n if (status != napi_ok) {\n break;\n }\n}\nWhen nesting scopes, there are cases where a handle from an\ninner scope needs to live beyond the lifespan of that scope. N-API supports an\n'escapable scope' in order to support this case. An escapable scope\nallows one handle to be 'promoted' so that it 'escapes' the\ncurrent scope and the lifespan of the handle changes from the current\nscope to that of the outer scope.
\nThe methods available to open/close escapable scopes are\nnapi_open_escapable_handle_scope and\nnapi_close_escapable_handle_scope.
The request to promote a handle is made through napi_escape_handle which\ncan only be called once.
NAPI_EXTERN napi_status napi_open_handle_scope(napi_env env,\n napi_handle_scope* result);\n[in] env: The environment that the API is invoked under.[out] result: napi_value representing the new scope.Returns napi_ok if the API succeeded.
This API open a new scope.
", "type": "module", "displayName": "napi_open_handle_scope" }, { "textRaw": "napi_close_handle_scope", "name": "napi_close_handle_scope", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_close_handle_scope(napi_env env,\n napi_handle_scope scope);\n[in] env: The environment that the API is invoked under.[in] scope: napi_value representing the scope to be closed.Returns napi_ok if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the\nreverse order from which they were created.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_close_handle_scope" }, { "textRaw": "napi_open_escapable_handle_scope", "name": "napi_open_escapable_handle_scope", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\n napi_open_escapable_handle_scope(napi_env env,\n napi_handle_scope* result);\n[in] env: The environment that the API is invoked under.[out] result: napi_value representing the new scope.Returns napi_ok if the API succeeded.
This API open a new scope from which one object can be promoted\nto the outer scope.
", "type": "module", "displayName": "napi_open_escapable_handle_scope" }, { "textRaw": "napi_close_escapable_handle_scope", "name": "napi_close_escapable_handle_scope", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\n napi_close_escapable_handle_scope(napi_env env,\n napi_handle_scope scope);\n[in] env: The environment that the API is invoked under.[in] scope: napi_value representing the scope to be closed.Returns napi_ok if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the\nreverse order from which they were created.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_close_escapable_handle_scope" }, { "textRaw": "napi_escape_handle", "name": "napi_escape_handle", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_escape_handle(napi_env env,\n napi_escapable_handle_scope scope,\n napi_value escapee,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] scope: napi_value representing the current scope.[in] escapee: napi_value representing the JavaScript Object to be\nescaped.[out] result: napi_value representing the handle to the escaped\nObject in the outer scope.Returns napi_ok if the API succeeded.
This API promotes the handle to the JavaScript object so that it is valid\nfor the lifetime of the outer scope. It can only be called once per scope.\nIf it is called more than once an error will be returned.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_escape_handle" } ], "type": "module", "displayName": "Making handle lifespan shorter than that of the native method" }, { "textRaw": "References to objects with a lifespan longer than that of the native method", "name": "references_to_objects_with_a_lifespan_longer_than_that_of_the_native_method", "desc": "In some cases an addon will need to be able to create and reference objects\nwith a lifespan longer than that of a single native method invocation. For\nexample, to create a constructor and later use that constructor\nin a request to creates instances, it must be possible to reference\nthe constructor object across many different instance creation requests. This\nwould not be possible with a normal handle returned as a napi_value as\ndescribed in the earlier section. The lifespan of a normal handle is\nmanaged by scopes and all scopes must be closed before the end of a native\nmethod.
N-API provides methods to create persistent references to an object.\nEach persistent reference has an associated count with a value of 0\nor higher. The count determines if the reference will keep\nthe corresponding object live. References with a count of 0 do not\nprevent the object from being collected and are often called 'weak'\nreferences. Any count greater than 0 will prevent the object\nfrom being collected.
\nReferences can be created with an initial reference count. The count can\nthen be modified through napi_reference_ref and\nnapi_reference_unref. If an object is collected while the count\nfor a reference is 0, all subsequent calls to\nget the object associated with the reference napi_get_reference_value\nwill return NULL for the returned napi_value. An attempt to call\nnapi_reference_ref for a reference whose object has been collected\nwill result in an error.
References must be deleted once they are no longer required by the addon. When\na reference is deleted it will no longer prevent the corresponding object from\nbeing collected. Failure to delete a persistent reference will result in\na 'memory leak' with both the native memory for the persistent reference and\nthe corresponding object on the heap being retained forever.
\nThere can be multiple persistent references created which refer to the same\nobject, each of which will either keep the object live or not based on its\nindividual count.
", "modules": [ { "textRaw": "napi_create_reference", "name": "napi_create_reference", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_create_reference(napi_env env,\n napi_value value,\n int initial_refcount,\n napi_ref* result);\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing the Object to which we want\na reference.[in] initial_refcount: Initial reference count for the new reference.[out] result: napi_ref pointing to the new reference.Returns napi_ok if the API succeeded.
This API create a new reference with the specified reference count\nto the Object passed in.
NAPI_EXTERN napi_status napi_delete_reference(napi_env env, napi_ref ref);\n[in] env: The environment that the API is invoked under.[in] ref: napi_ref to be deleted.Returns napi_ok if the API succeeded.
This API deletes the reference passed in.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_delete_reference" }, { "textRaw": "napi_reference_ref", "name": "napi_reference_ref", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_reference_ref(napi_env env,\n napi_ref ref,\n int* result);\n[in] env: The environment that the API is invoked under.[in] ref: napi_ref for which the reference count will be incremented.[out] result: The new reference count.Returns napi_ok if the API succeeded.
This API increments the reference count for the reference\npassed in and returns the resulting reference count.
", "type": "module", "displayName": "napi_reference_ref" }, { "textRaw": "napi_reference_unref", "name": "napi_reference_unref", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_reference_unref(napi_env env,\n napi_ref ref,\n int* result);\n[in] env: The environment that the API is invoked under.[in] ref: napi_ref for which the reference count will be decremented.[out] result: The new reference count.Returns napi_ok if the API succeeded.
This API decrements the reference count for the reference\npassed in and returns the resulting reference count.
", "type": "module", "displayName": "napi_reference_unref" }, { "textRaw": "napi_get_reference_value", "name": "napi_get_reference_value", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_get_reference_value(napi_env env,\n napi_ref ref,\n napi_value* result);\nthe napi_value passed in or out of these methods is a handle to the\nobject to which the reference is related.
[in] env: The environment that the API is invoked under.[in] ref: napi_ref for which we requesting the corresponding Object.[out] result: The napi_value for the Object referenced by the\nnapi_ref.Returns napi_ok if the API succeeded.
If still valid, this API returns the napi_value representing the\nJavaScript Object associated with the napi_ref. Otherwise, result\nwill be NULL.
While a Node.js process typically releases all its resources when exiting,\nembedders of Node.js, or future Worker support, may require addons to register\nclean-up hooks that will be run once the current Node.js instance exits.
\nN-API provides functions for registering and un-registering such callbacks.\nWhen those callbacks are run, all resources that are being held by the addon\nshould be freed up.
", "modules": [ { "textRaw": "napi_add_env_cleanup_hook", "name": "napi_add_env_cleanup_hook", "meta": { "added": [ "v10.2.0" ], "napiVersion": [ 3 ], "changes": [] }, "desc": "NODE_EXTERN napi_status napi_add_env_cleanup_hook(napi_env env,\n void (*fun)(void* arg),\n void* arg);\nRegisters fun as a function to be run with the arg parameter once the\ncurrent Node.js environment exits.
A function can safely be specified multiple times with different\narg values. In that case, it will be called multiple times as well.\nProviding the same fun and arg values multiple times is not allowed\nand will lead the process to abort.
The hooks will be called in reverse order, i.e. the most recently added one\nwill be called first.
\nRemoving this hook can be done by using napi_remove_env_cleanup_hook.\nTypically, that happens when the resource for which this hook was added\nis being torn down anyway.
NAPI_EXTERN napi_status napi_remove_env_cleanup_hook(napi_env env,\n void (*fun)(void* arg),\n void* arg);\nUnregisters fun as a function to be run with the arg parameter once the\ncurrent Node.js environment exits. Both the argument and the function value\nneed to be exact matches.
The function must have originally been registered\nwith napi_add_env_cleanup_hook, otherwise the process will abort.
N-API modules are registered in a manner similar to other modules\nexcept that instead of using the NODE_MODULE macro the following\nis used:
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)\nThe next difference is the signature for the Init method. For a N-API\nmodule it is as follows:
napi_value Init(napi_env env, napi_value exports);\nThe return value from Init is treated as the exports object for the module.\nThe Init method is passed an empty object via the exports parameter as a\nconvenience. If Init returns NULL, the parameter passed as exports is\nexported by the module. N-API modules cannot modify the module object but can\nspecify anything as the exports property of the module.
To add the method hello as a function so that it can be called as a method\nprovided by the addon:
napi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n napi_property_descriptor desc =\n {\"hello\", NULL, Method, NULL, NULL, NULL, napi_default, NULL};\n status = napi_define_properties(env, exports, 1, &desc);\n if (status != napi_ok) return NULL;\n return exports;\n}\nTo set a function to be returned by the require() for the addon:
napi_value Init(napi_env env, napi_value exports) {\n napi_value method;\n napi_status status;\n status = napi_create_function(env, \"exports\", NAPI_AUTO_LENGTH, Method, NULL, &method);\n if (status != napi_ok) return NULL;\n return method;\n}\nTo define a class so that new instances can be created (often used with\nObject Wrap):
\n// NOTE: partial example, not all referenced code is included\nnapi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n napi_property_descriptor properties[] = {\n { \"value\", NULL, NULL, GetValue, SetValue, NULL, napi_default, NULL },\n DECLARE_NAPI_METHOD(\"plusOne\", PlusOne),\n DECLARE_NAPI_METHOD(\"multiply\", Multiply),\n };\n\n napi_value cons;\n status =\n napi_define_class(env, \"MyObject\", New, NULL, 3, properties, &cons);\n if (status != napi_ok) return NULL;\n\n status = napi_create_reference(env, cons, 1, &constructor);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"MyObject\", cons);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\nIf the module will be loaded multiple times during the lifetime of the Node.js\nprocess, use the NAPI_MODULE_INIT macro to initialize the module:
NAPI_MODULE_INIT() {\n napi_value answer;\n napi_status result;\n\n status = napi_create_int64(env, 42, &answer);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"answer\", answer);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\nThis macro includes NAPI_MODULE, and declares an Init function with a\nspecial name and with visibility beyond the addon. This will allow Node.js to\ninitialize the module even if it is loaded multiple times.
There are a few design considerations when declaring a module that may be loaded\nmultiple times. The documentation of context-aware addons provides more\ndetails.
\nThe variables env and exports will be available inside the function body\nfollowing the macro invocation.
For more details on setting properties on objects, see the section on\nWorking with JavaScript Properties.
\nFor more details on building addon modules in general, refer to the existing\nAPI.
", "type": "misc", "displayName": "Module registration" }, { "textRaw": "Working with JavaScript Values", "name": "working_with_javascript_values", "desc": "N-API exposes a set of APIs to create all types of JavaScript values.\nSome of these types are documented under\nSection 6\nof the ECMAScript Language Specification.
\nFundamentally, these APIs are used to do one of the following:\n1. Create a new JavaScript object\n2. Convert from a primitive C type to an N-API value\n3. Convert from N-API value to a primitive C type\n4. Get global instances including undefined and null
N-API values are represented by the type napi_value.\nAny N-API call that requires a JavaScript value takes in a napi_value.\nIn some cases, the API does check the type of the napi_value up-front.\nHowever, for better performance, it's better for the caller to make sure that\nthe napi_value in question is of the JavaScript type expected by the API.
typedef enum {\n // ES6 types (corresponds to typeof)\n napi_undefined,\n napi_null,\n napi_boolean,\n napi_number,\n napi_string,\n napi_symbol,\n napi_object,\n napi_function,\n napi_external,\n napi_bigint,\n} napi_valuetype;\nDescribes the type of a napi_value. This generally corresponds to the types\ndescribed in\nSection 6.1 of\nthe ECMAScript Language Specification.\nIn addition to types in that section, napi_valuetype can also represent\nFunctions and Objects with external data.
A JavaScript value of type napi_external appears in JavaScript as a plain\nobject such that no properties can be set on it, and no prototype.
typedef enum {\n napi_int8_array,\n napi_uint8_array,\n napi_uint8_clamped_array,\n napi_int16_array,\n napi_uint16_array,\n napi_int32_array,\n napi_uint32_array,\n napi_float32_array,\n napi_float64_array,\n napi_bigint64_array,\n napi_biguint64_array,\n} napi_typedarray_type;\nThis represents the underlying binary scalar datatype of the TypedArray.\nElements of this enum correspond to\nSection 22.2 of the ECMAScript Language Specification.
napi_status napi_create_array(napi_env env, napi_value* result)\n[in] env: The environment that the N-API call is invoked under.[out] result: A napi_value representing a JavaScript Array.Returns napi_ok if the API succeeded.
This API returns an N-API value corresponding to a JavaScript Array type.\nJavaScript arrays are described in\nSection 22.1 of the ECMAScript Language Specification.
napi_status napi_create_array_with_length(napi_env env,\n size_t length,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] length: The initial length of the Array.[out] result: A napi_value representing a JavaScript Array.Returns napi_ok if the API succeeded.
This API returns an N-API value corresponding to a JavaScript Array type.\nThe Array's length property is set to the passed-in length parameter.\nHowever, the underlying buffer is not guaranteed to be pre-allocated by the VM\nwhen the array is created - that behavior is left to the underlying VM\nimplementation.\nIf the buffer must be a contiguous block of memory that can be\ndirectly read and/or written via C, consider using\nnapi_create_external_arraybuffer.
JavaScript arrays are described in\nSection 22.1 of the ECMAScript Language Specification.
", "type": "module", "displayName": "napi_create_array_with_length" }, { "textRaw": "napi_create_arraybuffer", "name": "napi_create_arraybuffer", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_create_arraybuffer(napi_env env,\n size_t byte_length,\n void** data,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] length: The length in bytes of the array buffer to create.[out] data: Pointer to the underlying byte buffer of the ArrayBuffer.[out] result: A napi_value representing a JavaScript ArrayBuffer.Returns napi_ok if the API succeeded.
This API returns an N-API value corresponding to a JavaScript ArrayBuffer.\nArrayBuffers are used to represent fixed-length binary data buffers. They are\nnormally used as a backing-buffer for TypedArray objects.\nThe ArrayBuffer allocated will have an underlying byte buffer whose size is\ndetermined by the length parameter that's passed in.\nThe underlying buffer is optionally returned back to the caller in case the\ncaller wants to directly manipulate the buffer. This buffer can only be\nwritten to directly from native code. To write to this buffer from JavaScript,\na typed array or DataView object would need to be created.
JavaScript ArrayBuffer objects are described in\nSection 24.1 of the ECMAScript Language Specification.
napi_status napi_create_buffer(napi_env env,\n size_t size,\n void** data,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] size: Size in bytes of the underlying buffer.[out] data: Raw pointer to the underlying buffer.[out] result: A napi_value representing a node::Buffer.Returns napi_ok if the API succeeded.
This API allocates a node::Buffer object. While this is still a\nfully-supported data structure, in most cases using a TypedArray will suffice.
napi_status napi_create_buffer_copy(napi_env env,\n size_t length,\n const void* data,\n void** result_data,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] size: Size in bytes of the input buffer (should be the same as the\nsize of the new buffer).[in] data: Raw pointer to the underlying buffer to copy from.[out] result_data: Pointer to the new Buffer's underlying data buffer.[out] result: A napi_value representing a node::Buffer.Returns napi_ok if the API succeeded.
This API allocates a node::Buffer object and initializes it with data copied\nfrom the passed-in buffer. While this is still a fully-supported data\nstructure, in most cases using a TypedArray will suffice.
napi_status napi_create_date(napi_env env,\n double time,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] time: ECMAScript time value in milliseconds since 01 January, 1970 UTC.[out] result: A napi_value representing a JavaScript Date.Returns napi_ok if the API succeeded.
This API allocates a JavaScript Date object.
JavaScript Date objects are described in\nSection 20.3 of the ECMAScript Language Specification.
napi_status napi_create_external(napi_env env,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] data: Raw pointer to the external data.[in] finalize_cb: Optional callback to call when the external value\nis being collected.[in] finalize_hint: Optional hint to pass to the finalize callback\nduring collection.[out] result: A napi_value representing an external value.Returns napi_ok if the API succeeded.
This API allocates a JavaScript value with external data attached to it. This\nis used to pass external data through JavaScript code, so it can be retrieved\nlater by native code. The API allows the caller to pass in a finalize callback,\nin case the underlying native resource needs to be cleaned up when the external\nJavaScript value gets collected.
\nThe created value is not an object, and therefore does not support additional\nproperties. It is considered a distinct value type: calling napi_typeof() with\nan external value yields napi_external.
napi_status\nnapi_create_external_arraybuffer(napi_env env,\n void* external_data,\n size_t byte_length,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] external_data: Pointer to the underlying byte buffer of the\nArrayBuffer.[in] byte_length: The length in bytes of the underlying buffer.[in] finalize_cb: Optional callback to call when the ArrayBuffer is\nbeing collected.[in] finalize_hint: Optional hint to pass to the finalize callback\nduring collection.[out] result: A napi_value representing a JavaScript ArrayBuffer.Returns napi_ok if the API succeeded.
This API returns an N-API value corresponding to a JavaScript ArrayBuffer.\nThe underlying byte buffer of the ArrayBuffer is externally allocated and\nmanaged. The caller must ensure that the byte buffer remains valid until the\nfinalize callback is called.
JavaScript ArrayBuffers are described in\nSection 24.1 of the ECMAScript Language Specification.
napi_status napi_create_external_buffer(napi_env env,\n size_t length,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] length: Size in bytes of the input buffer (should be the same as\nthe size of the new buffer).[in] data: Raw pointer to the underlying buffer to copy from.[in] finalize_cb: Optional callback to call when the ArrayBuffer is\nbeing collected.[in] finalize_hint: Optional hint to pass to the finalize callback\nduring collection.[out] result: A napi_value representing a node::Buffer.Returns napi_ok if the API succeeded.
This API allocates a node::Buffer object and initializes it with data\nbacked by the passed in buffer. While this is still a fully-supported data\nstructure, in most cases using a TypedArray will suffice.
For Node.js >=4 Buffers are Uint8Arrays.
napi_status napi_create_object(napi_env env, napi_value* result)\n[in] env: The environment that the API is invoked under.[out] result: A napi_value representing a JavaScript Object.Returns napi_ok if the API succeeded.
This API allocates a default JavaScript Object.\nIt is the equivalent of doing new Object() in JavaScript.
The JavaScript Object type is described in\nSection 6.1.7 of the\nECMAScript Language Specification.
napi_status napi_create_symbol(napi_env env,\n napi_value description,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] description: Optional napi_value which refers to a JavaScript\nString to be set as the description for the symbol.[out] result: A napi_value representing a JavaScript Symbol.Returns napi_ok if the API succeeded.
This API creates a JavaScript Symbol object from a UTF8-encoded C string.
The JavaScript Symbol type is described in\nSection 19.4\nof the ECMAScript Language Specification.
napi_status napi_create_typedarray(napi_env env,\n napi_typedarray_type type,\n size_t length,\n napi_value arraybuffer,\n size_t byte_offset,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] type: Scalar datatype of the elements within the TypedArray.[in] length: Number of elements in the TypedArray.[in] arraybuffer: ArrayBuffer underlying the typed array.[in] byte_offset: The byte offset within the ArrayBuffer from which to\nstart projecting the TypedArray.[out] result: A napi_value representing a JavaScript TypedArray.Returns napi_ok if the API succeeded.
This API creates a JavaScript TypedArray object over an existing\nArrayBuffer. TypedArray objects provide an array-like view over an\nunderlying data buffer where each element has the same underlying binary scalar\ndatatype.
It's required that (length * size_of_element) + byte_offset should\nbe <= the size in bytes of the array passed in. If not, a RangeError exception\nis raised.
JavaScript TypedArray objects are described in\nSection 22.2 of the ECMAScript Language Specification.
napi_status napi_create_dataview(napi_env env,\n size_t byte_length,\n napi_value arraybuffer,\n size_t byte_offset,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] length: Number of elements in the DataView.[in] arraybuffer: ArrayBuffer underlying the DataView.[in] byte_offset: The byte offset within the ArrayBuffer from which to\nstart projecting the DataView.[out] result: A napi_value representing a JavaScript DataView.Returns napi_ok if the API succeeded.
This API creates a JavaScript DataView object over an existing ArrayBuffer.\nDataView objects provide an array-like view over an underlying data buffer,\nbut one which allows items of different size and type in the ArrayBuffer.
It is required that byte_length + byte_offset is less than or equal to the\nsize in bytes of the array passed in. If not, a RangeError exception is\nraised.
JavaScript DataView objects are described in\nSection 24.3 of the ECMAScript Language Specification.
napi_status napi_create_int32(napi_env env, int32_t value, napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: Integer value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript Number.Returns napi_ok if the API succeeded.
This API is used to convert from the C int32_t type to the JavaScript\nNumber type.
The JavaScript Number type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_uint32(napi_env env, uint32_t value, napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: Unsigned integer value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript Number.Returns napi_ok if the API succeeded.
This API is used to convert from the C uint32_t type to the JavaScript\nNumber type.
The JavaScript Number type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_int64(napi_env env, int64_t value, napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: Integer value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript Number.Returns napi_ok if the API succeeded.
This API is used to convert from the C int64_t type to the JavaScript\nNumber type.
The JavaScript Number type is described in Section 6.1.6\nof the ECMAScript Language Specification. Note the complete range of int64_t\ncannot be represented with full precision in JavaScript. Integer values\noutside the range of\nNumber.MIN_SAFE_INTEGER\n-(2^53 - 1) -\nNumber.MAX_SAFE_INTEGER\n(2^53 - 1) will lose precision.
napi_status napi_create_double(napi_env env, double value, napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: Double-precision value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript Number.Returns napi_ok if the API succeeded.
This API is used to convert from the C double type to the JavaScript\nNumber type.
The JavaScript Number type is described in\nSection 6.1.6 of the ECMAScript Language Specification.
napi_status napi_create_bigint_int64(napi_env env,\n int64_t value,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] value: Integer value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript BigInt.Returns napi_ok if the API succeeded.
This API converts the C int64_t type to the JavaScript BigInt type.
napi_status napi_create_bigint_uint64(napi_env env,\n uint64_t value,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] value: Unsigned integer value to be represented in JavaScript.[out] result: A napi_value representing a JavaScript BigInt.Returns napi_ok if the API succeeded.
This API converts the C uint64_t type to the JavaScript BigInt type.
napi_status napi_create_bigint_words(napi_env env,\n int sign_bit,\n size_t word_count,\n const uint64_t* words,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] sign_bit: Determines if the resulting BigInt will be positive or\nnegative.[in] word_count: The length of the words array.[in] words: An array of uint64_t little-endian 64-bit words.[out] result: A napi_value representing a JavaScript BigInt.Returns napi_ok if the API succeeded.
This API converts an array of unsigned 64-bit words into a single BigInt\nvalue.
The resulting BigInt is calculated as: (–1)sign_bit (words[0]\n× (264)0 + words[1] × (264)1 + …)
napi_status napi_create_string_latin1(napi_env env,\n const char* str,\n size_t length,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] str: Character buffer representing an ISO-8859-1-encoded string.[in] length: The length of the string in bytes, or\nNAPI_AUTO_LENGTH if it is null-terminated.[out] result: A napi_value representing a JavaScript String.Returns napi_ok if the API succeeded.
This API creates a JavaScript String object from an ISO-8859-1-encoded C\nstring. The native string is copied.
The JavaScript String type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_create_string_utf16(napi_env env,\n const char16_t* str,\n size_t length,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] str: Character buffer representing a UTF16-LE-encoded string.[in] length: The length of the string in two-byte code units, or\nNAPI_AUTO_LENGTH if it is null-terminated.[out] result: A napi_value representing a JavaScript String.Returns napi_ok if the API succeeded.
This API creates a JavaScript String object from a UTF16-LE-encoded C string.\nThe native string is copied.
The JavaScript String type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_create_string_utf8(napi_env env,\n const char* str,\n size_t length,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] str: Character buffer representing a UTF8-encoded string.[in] length: The length of the string in bytes, or NAPI_AUTO_LENGTH\nif it is null-terminated.[out] result: A napi_value representing a JavaScript String.Returns napi_ok if the API succeeded.
This API creates a JavaScript String object from a UTF8-encoded C string.\nThe native string is copied.
The JavaScript String type is described in\nSection 6.1.4 of the ECMAScript Language Specification.
napi_status napi_get_array_length(napi_env env,\n napi_value value,\n uint32_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing the JavaScript Array whose length is\nbeing queried.[out] result: uint32 representing length of the array.Returns napi_ok if the API succeeded.
This API returns the length of an array.
\nArray length is described in\nSection 22.1.4.1\nof the ECMAScript Language Specification.
napi_status napi_get_arraybuffer_info(napi_env env,\n napi_value arraybuffer,\n void** data,\n size_t* byte_length)\n[in] env: The environment that the API is invoked under.[in] arraybuffer: napi_value representing the ArrayBuffer being queried.[out] data: The underlying data buffer of the ArrayBuffer.[out] byte_length: Length in bytes of the underlying data buffer.Returns napi_ok if the API succeeded.
This API is used to retrieve the underlying data buffer of an ArrayBuffer and\nits length.
WARNING: Use caution while using this API. The lifetime of the underlying data\nbuffer is managed by the ArrayBuffer even after it's returned. A\npossible safe way to use this API is in conjunction with\nnapi_create_reference, which can be used to guarantee control over the\nlifetime of the ArrayBuffer. It's also safe to use the returned data buffer\nwithin the same callback as long as there are no calls to other APIs that might\ntrigger a GC.
napi_status napi_get_buffer_info(napi_env env,\n napi_value value,\n void** data,\n size_t* length)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing the node::Buffer being queried.[out] data: The underlying data buffer of the node::Buffer.[out] length: Length in bytes of the underlying data buffer.Returns napi_ok if the API succeeded.
This API is used to retrieve the underlying data buffer of a node::Buffer\nand it's length.
Warning: Use caution while using this API since the underlying data buffer's\nlifetime is not guaranteed if it's managed by the VM.
", "type": "module", "displayName": "napi_get_buffer_info" }, { "textRaw": "napi_get_prototype", "name": "napi_get_prototype", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_prototype(napi_env env,\n napi_value object,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] object: napi_value representing JavaScript Object whose prototype\nto return. This returns the equivalent of Object.getPrototypeOf (which is\nnot the same as the function's prototype property).[out] result: napi_value representing prototype of the given object.Returns napi_ok if the API succeeded.
napi_status napi_get_typedarray_info(napi_env env,\n napi_value typedarray,\n napi_typedarray_type* type,\n size_t* length,\n void** data,\n napi_value* arraybuffer,\n size_t* byte_offset)\n[in] env: The environment that the API is invoked under.[in] typedarray: napi_value representing the TypedArray whose\nproperties to query.[out] type: Scalar datatype of the elements within the TypedArray.[out] length: The number of elements in the TypedArray.[out] data: The data buffer underlying the TypedArray adjusted by\nthe byte_offset value so that it points to the first element in the\nTypedArray.[out] arraybuffer: The ArrayBuffer underlying the TypedArray.[out] byte_offset: The byte offset within the underlying native array\nat which the first element of the arrays is located. The value for the data\nparameter has already been adjusted so that data points to the first element\nin the array. Therefore, the first byte of the native array would be at\ndata - byte_offset.Returns napi_ok if the API succeeded.
This API returns various properties of a typed array.
\nWarning: Use caution while using this API since the underlying data buffer\nis managed by the VM.
", "type": "module", "displayName": "napi_get_typedarray_info" }, { "textRaw": "napi_get_dataview_info", "name": "napi_get_dataview_info", "meta": { "added": [ "v8.3.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_dataview_info(napi_env env,\n napi_value dataview,\n size_t* byte_length,\n void** data,\n napi_value* arraybuffer,\n size_t* byte_offset)\n[in] env: The environment that the API is invoked under.[in] dataview: napi_value representing the DataView whose\nproperties to query.[out] byte_length: Number of bytes in the DataView.[out] data: The data buffer underlying the DataView.[out] arraybuffer: ArrayBuffer underlying the DataView.[out] byte_offset: The byte offset within the data buffer from which\nto start projecting the DataView.Returns napi_ok if the API succeeded.
This API returns various properties of a DataView.
napi_status napi_get_date_value(napi_env env,\n napi_value value,\n double* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing a JavaScript Date.[out] result: Time value as a double represented as milliseconds\nsince midnight at the beginning of 01 January, 1970 UTC.Returns napi_ok if the API succeeded. If a non-date napi_value is passed\nin it returns napi_date_expected.
This API returns the C double primitive of time value for the given JavaScript\nDate.
napi_status napi_get_value_bool(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript Boolean.[out] result: C boolean primitive equivalent of the given JavaScript\nBoolean.Returns napi_ok if the API succeeded. If a non-boolean napi_value is\npassed in it returns napi_boolean_expected.
This API returns the C boolean primitive equivalent of the given JavaScript\nBoolean.
napi_status napi_get_value_double(napi_env env,\n napi_value value,\n double* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript Number.[out] result: C double primitive equivalent of the given JavaScript\nNumber.Returns napi_ok if the API succeeded. If a non-number napi_value is passed\nin it returns napi_number_expected.
This API returns the C double primitive equivalent of the given JavaScript\nNumber.
napi_status napi_get_value_bigint_int64(napi_env env,\n napi_value value,\n int64_t* result,\n bool* lossless);\n[in] env: The environment that the API is invoked under[in] value: napi_value representing JavaScript BigInt.[out] result: C int64_t primitive equivalent of the given JavaScript\nBigInt.[out] lossless: Indicates whether the BigInt value was converted\nlosslessly.Returns napi_ok if the API succeeded. If a non-BigInt is passed in it\nreturns napi_bigint_expected.
This API returns the C int64_t primitive equivalent of the given JavaScript\nBigInt. If needed it will truncate the value, setting lossless to false.
napi_status napi_get_value_bigint_uint64(napi_env env,\n napi_value value,\n uint64_t* result,\n bool* lossless);\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript BigInt.[out] result: C uint64_t primitive equivalent of the given JavaScript\nBigInt.[out] lossless: Indicates whether the BigInt value was converted\nlosslessly.Returns napi_ok if the API succeeded. If a non-BigInt is passed in it\nreturns napi_bigint_expected.
This API returns the C uint64_t primitive equivalent of the given JavaScript\nBigInt. If needed it will truncate the value, setting lossless to false.
napi_status napi_get_value_bigint_words(napi_env env,\n napi_value value,\n size_t* word_count,\n int* sign_bit,\n uint64_t* words);\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript BigInt.[out] sign_bit: Integer representing if the JavaScript BigInt is positive\nor negative.[in/out] word_count: Must be initialized to the length of the words\narray. Upon return, it will be set to the actual number of words that\nwould be needed to store this BigInt.[out] words: Pointer to a pre-allocated 64-bit word array.Returns napi_ok if the API succeeded.
This API converts a single BigInt value into a sign bit, 64-bit little-endian\narray, and the number of elements in the array. sign_bit and words may be\nboth set to NULL, in order to get only word_count.
napi_status napi_get_value_external(napi_env env,\n napi_value value,\n void** result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript external value.[out] result: Pointer to the data wrapped by the JavaScript external value.Returns napi_ok if the API succeeded. If a non-external napi_value is\npassed in it returns napi_invalid_arg.
This API retrieves the external data pointer that was previously passed to\nnapi_create_external().
napi_status napi_get_value_int32(napi_env env,\n napi_value value,\n int32_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript Number.[out] result: C int32 primitive equivalent of the given JavaScript\nNumber.Returns napi_ok if the API succeeded. If a non-number napi_value\nis passed in napi_number_expected.
This API returns the C int32 primitive equivalent\nof the given JavaScript Number.
If the number exceeds the range of the 32 bit integer, then the result is\ntruncated to the equivalent of the bottom 32 bits. This can result in a large\npositive number becoming a negative number if the value is > 2^31 -1.
\nNon-finite number values (NaN, +Infinity, or -Infinity) set the\nresult to zero.
napi_status napi_get_value_int64(napi_env env,\n napi_value value,\n int64_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript Number.[out] result: C int64 primitive equivalent of the given JavaScript\nNumber.Returns napi_ok if the API succeeded. If a non-number napi_value\nis passed in it returns napi_number_expected.
This API returns the C int64 primitive equivalent of the given JavaScript\nNumber.
Number values outside the range of\nNumber.MIN_SAFE_INTEGER\n-(2^53 - 1) -\nNumber.MAX_SAFE_INTEGER\n(2^53 - 1) will lose precision.
Non-finite number values (NaN, +Infinity, or -Infinity) set the\nresult to zero.
napi_status napi_get_value_string_latin1(napi_env env,\n napi_value value,\n char* buf,\n size_t bufsize,\n size_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript string.[in] buf: Buffer to write the ISO-8859-1-encoded string into. If NULL is\npassed in, the length of the string (in bytes) is returned.[in] bufsize: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[out] result: Number of bytes copied into the buffer, excluding the null\nterminator.Returns napi_ok if the API succeeded. If a non-String napi_value\nis passed in it returns napi_string_expected.
This API returns the ISO-8859-1-encoded string corresponding the value passed\nin.
", "type": "module", "displayName": "napi_get_value_string_latin1" }, { "textRaw": "napi_get_value_string_utf8", "name": "napi_get_value_string_utf8", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_string_utf8(napi_env env,\n napi_value value,\n char* buf,\n size_t bufsize,\n size_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript string.[in] buf: Buffer to write the UTF8-encoded string into. If NULL is passed\nin, the length of the string (in bytes) is returned.[in] bufsize: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[out] result: Number of bytes copied into the buffer, excluding the null\nterminator.Returns napi_ok if the API succeeded. If a non-String napi_value\nis passed in it returns napi_string_expected.
This API returns the UTF8-encoded string corresponding the value passed in.
", "type": "module", "displayName": "napi_get_value_string_utf8" }, { "textRaw": "napi_get_value_string_utf16", "name": "napi_get_value_string_utf16", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_string_utf16(napi_env env,\n napi_value value,\n char16_t* buf,\n size_t bufsize,\n size_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript string.[in] buf: Buffer to write the UTF16-LE-encoded string into. If NULL is\npassed in, the length of the string (in 2-byte code units) is returned.[in] bufsize: Size of the destination buffer. When this value is\ninsufficient, the returned string will be truncated.[out] result: Number of 2-byte code units copied into the buffer, excluding\nthe null terminator.Returns napi_ok if the API succeeded. If a non-String napi_value\nis passed in it returns napi_string_expected.
This API returns the UTF16-encoded string corresponding the value passed in.
", "type": "module", "displayName": "napi_get_value_string_utf16" }, { "textRaw": "napi_get_value_uint32", "name": "napi_get_value_uint32", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_value_uint32(napi_env env,\n napi_value value,\n uint32_t* result)\n[in] env: The environment that the API is invoked under.[in] value: napi_value representing JavaScript Number.[out] result: C primitive equivalent of the given napi_value as a\nuint32_t.Returns napi_ok if the API succeeded. If a non-number napi_value\nis passed in it returns napi_number_expected.
This API returns the C primitive equivalent of the given napi_value as a\nuint32_t.
napi_status napi_get_boolean(napi_env env, bool value, napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: The value of the boolean to retrieve.[out] result: napi_value representing JavaScript Boolean singleton to\nretrieve.Returns napi_ok if the API succeeded.
This API is used to return the JavaScript singleton object that is used to\nrepresent the given boolean value.
", "type": "module", "displayName": "napi_get_boolean" }, { "textRaw": "napi_get_global", "name": "napi_get_global", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_global(napi_env env, napi_value* result)\n[in] env: The environment that the API is invoked under.[out] result: napi_value representing JavaScript global object.Returns napi_ok if the API succeeded.
This API returns the global object.
napi_status napi_get_null(napi_env env, napi_value* result)\n[in] env: The environment that the API is invoked under.[out] result: napi_value representing JavaScript null object.Returns napi_ok if the API succeeded.
This API returns the null object.
napi_status napi_get_undefined(napi_env env, napi_value* result)\n[in] env: The environment that the API is invoked under.[out] result: napi_value representing JavaScript Undefined value.Returns napi_ok if the API succeeded.
This API returns the Undefined object.
", "type": "module", "displayName": "napi_get_undefined" } ], "type": "module", "displayName": "Functions to get global instances" } ], "type": "misc", "displayName": "Working with JavaScript Values" }, { "textRaw": "Working with JavaScript Values - Abstract Operations", "name": "working_with_javascript_values_-_abstract_operations", "desc": "N-API exposes a set of APIs to perform some abstract operations on JavaScript\nvalues. Some of these operations are documented under\nSection 7\nof the ECMAScript Language Specification.
\nThese APIs support doing one of the following:\n1. Coerce JavaScript values to specific JavaScript types (such as Number or\nString).\n2. Check the type of a JavaScript value.\n3. Check for equality between two JavaScript values.
napi_status napi_coerce_to_bool(napi_env env,\n napi_value value,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to coerce.[out] result: napi_value representing the coerced JavaScript Boolean.Returns napi_ok if the API succeeded.
This API implements the abstract operation ToBoolean() as defined in\nSection 7.1.2\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object.
napi_status napi_coerce_to_number(napi_env env,\n napi_value value,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to coerce.[out] result: napi_value representing the coerced JavaScript Number.Returns napi_ok if the API succeeded.
This API implements the abstract operation ToNumber() as defined in\nSection 7.1.3\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object.
napi_status napi_coerce_to_object(napi_env env,\n napi_value value,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to coerce.[out] result: napi_value representing the coerced JavaScript Object.Returns napi_ok if the API succeeded.
This API implements the abstract operation ToObject() as defined in\nSection 7.1.13\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object.
napi_status napi_coerce_to_string(napi_env env,\n napi_value value,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to coerce.[out] result: napi_value representing the coerced JavaScript String.Returns napi_ok if the API succeeded.
This API implements the abstract operation ToString() as defined in\nSection 7.1.13\nof the ECMAScript Language Specification.\nThis API can be re-entrant if getters are defined on the passed-in Object.
napi_status napi_typeof(napi_env env, napi_value value, napi_valuetype* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value whose type to query.[out] result: The type of the JavaScript value.Returns napi_ok if the API succeeded.
napi_invalid_arg if the type of value is not a known ECMAScript type and\nvalue is not an External value.This API represents behavior similar to invoking the typeof Operator on\nthe object as defined in Section 12.5.5 of the ECMAScript Language\nSpecification. However, it has support for detecting an External value.\nIf value has a type that is invalid, an error is returned.
napi_status napi_instanceof(napi_env env,\n napi_value object,\n napi_value constructor,\n bool* result)\n[in] env: The environment that the API is invoked under.[in] object: The JavaScript value to check.[in] constructor: The JavaScript function object of the constructor\nfunction to check against.[out] result: Boolean that is set to true if object instanceof constructor\nis true.Returns napi_ok if the API succeeded.
This API represents invoking the instanceof Operator on the object as\ndefined in\nSection 12.10.4\nof the ECMAScript Language Specification.
napi_status napi_is_array(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given object is an array.Returns napi_ok if the API succeeded.
This API represents invoking the IsArray operation on the object\nas defined in Section 7.2.2\nof the ECMAScript Language Specification.
napi_status napi_is_arraybuffer(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given object is an ArrayBuffer.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is an array buffer.
napi_status napi_is_buffer(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given napi_value represents a node::Buffer\nobject.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is a buffer.
napi_status napi_is_date(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given napi_value represents a JavaScript Date\nobject.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is a date.
napi_status napi_is_error(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given napi_value represents an Error object.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is an Error.
napi_status napi_is_typedarray(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given napi_value represents a TypedArray.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is a typed array.
napi_status napi_is_dataview(napi_env env, napi_value value, bool* result)\n[in] env: The environment that the API is invoked under.[in] value: The JavaScript value to check.[out] result: Whether the given napi_value represents a DataView.Returns napi_ok if the API succeeded.
This API checks if the Object passed in is a DataView.
napi_status napi_strict_equals(napi_env env,\n napi_value lhs,\n napi_value rhs,\n bool* result)\n[in] env: The environment that the API is invoked under.[in] lhs: The JavaScript value to check.[in] rhs: The JavaScript value to check against.[out] result: Whether the two napi_value objects are equal.Returns napi_ok if the API succeeded.
This API represents the invocation of the Strict Equality algorithm as\ndefined in\nSection 7.2.14\nof the ECMAScript Language Specification.
", "type": "module", "displayName": "napi_strict_equals" } ], "type": "misc", "displayName": "Working with JavaScript Values - Abstract Operations" }, { "textRaw": "Working with JavaScript Properties", "name": "working_with_javascript_properties", "desc": "N-API exposes a set of APIs to get and set properties on JavaScript\nobjects. Some of these types are documented under\nSection 7 of the\nECMAScript Language Specification.
\nProperties in JavaScript are represented as a tuple of a key and a value.\nFundamentally, all property keys in N-API can be represented in one of the\nfollowing forms:
\nuint32_tnapi_value. This can\nbe a napi_value representing a String, Number, or Symbol.N-API values are represented by the type napi_value.\nAny N-API call that requires a JavaScript value takes in a napi_value.\nHowever, it's the caller's responsibility to make sure that the\nnapi_value in question is of the JavaScript type expected by the API.
The APIs documented in this section provide a simple interface to\nget and set properties on arbitrary JavaScript objects represented by\nnapi_value.
For instance, consider the following JavaScript code snippet:
\nconst obj = {};\nobj.myProp = 123;\nThe equivalent can be done using N-API values with the following snippet:
\nnapi_status status = napi_generic_failure;\n\n// const obj = {}\nnapi_value obj, value;\nstatus = napi_create_object(env, &obj);\nif (status != napi_ok) return status;\n\n// Create a napi_value for 123\nstatus = napi_create_int32(env, 123, &value);\nif (status != napi_ok) return status;\n\n// obj.myProp = 123\nstatus = napi_set_named_property(env, obj, \"myProp\", value);\nif (status != napi_ok) return status;\nIndexed properties can be set in a similar manner. Consider the following\nJavaScript snippet:
\nconst arr = [];\narr[123] = 'hello';\nThe equivalent can be done using N-API values with the following snippet:
\nnapi_status status = napi_generic_failure;\n\n// const arr = [];\nnapi_value arr, value;\nstatus = napi_create_array(env, &arr);\nif (status != napi_ok) return status;\n\n// Create a napi_value for 'hello'\nstatus = napi_create_string_utf8(env, \"hello\", NAPI_AUTO_LENGTH, &value);\nif (status != napi_ok) return status;\n\n// arr[123] = 'hello';\nstatus = napi_set_element(env, arr, 123, value);\nif (status != napi_ok) return status;\nProperties can be retrieved using the APIs described in this section.\nConsider the following JavaScript snippet:
\nconst arr = [];\nconst value = arr[123];\nThe following is the approximate equivalent of the N-API counterpart:
\nnapi_status status = napi_generic_failure;\n\n// const arr = []\nnapi_value arr, value;\nstatus = napi_create_array(env, &arr);\nif (status != napi_ok) return status;\n\n// const value = arr[123]\nstatus = napi_get_element(env, arr, 123, &value);\nif (status != napi_ok) return status;\nFinally, multiple properties can also be defined on an object for performance\nreasons. Consider the following JavaScript:
\nconst obj = {};\nObject.defineProperties(obj, {\n 'foo': { value: 123, writable: true, configurable: true, enumerable: true },\n 'bar': { value: 456, writable: true, configurable: true, enumerable: true }\n});\nThe following is the approximate equivalent of the N-API counterpart:
\nnapi_status status = napi_status_generic_failure;\n\n// const obj = {};\nnapi_value obj;\nstatus = napi_create_object(env, &obj);\nif (status != napi_ok) return status;\n\n// Create napi_values for 123 and 456\nnapi_value fooValue, barValue;\nstatus = napi_create_int32(env, 123, &fooValue);\nif (status != napi_ok) return status;\nstatus = napi_create_int32(env, 456, &barValue);\nif (status != napi_ok) return status;\n\n// Set the properties\nnapi_property_descriptor descriptors[] = {\n { \"foo\", NULL, NULL, NULL, NULL, fooValue, napi_default, NULL },\n { \"bar\", NULL, NULL, NULL, NULL, barValue, napi_default, NULL }\n}\nstatus = napi_define_properties(env,\n obj,\n sizeof(descriptors) / sizeof(descriptors[0]),\n descriptors);\nif (status != napi_ok) return status;\ntypedef enum {\n napi_default = 0,\n napi_writable = 1 << 0,\n napi_enumerable = 1 << 1,\n napi_configurable = 1 << 2,\n\n // Used with napi_define_class to distinguish static properties\n // from instance properties. Ignored by napi_define_properties.\n napi_static = 1 << 10,\n} napi_property_attributes;\nnapi_property_attributes are flags used to control the behavior of properties\nset on a JavaScript object. Other than napi_static they correspond to the\nattributes listed in Section 6.1.7.1\nof the ECMAScript Language Specification.\nThey can be one or more of the following bitflags:
napi_default - Used to indicate that no explicit attributes are set on the\ngiven property. By default, a property is read only, not enumerable and not\nconfigurable.napi_writable - Used to indicate that a given property is writable.napi_enumerable - Used to indicate that a given property is enumerable.napi_configurable - Used to indicate that a given property is configurable,\nas defined in Section 6.1.7.1 of the ECMAScript Language Specification.napi_static - Used to indicate that the property will be defined as\na static property on a class as opposed to an instance property, which is the\ndefault. This is used only by napi_define_class. It is ignored by\nnapi_define_properties.typedef struct {\n // One of utf8name or name should be NULL.\n const char* utf8name;\n napi_value name;\n\n napi_callback method;\n napi_callback getter;\n napi_callback setter;\n napi_value value;\n\n napi_property_attributes attributes;\n void* data;\n} napi_property_descriptor;\nutf8name: Optional String describing the key for the property,\nencoded as UTF8. One of utf8name or name must be provided for the\nproperty.name: Optional napi_value that points to a JavaScript string or symbol\nto be used as the key for the property. One of utf8name or name must\nbe provided for the property.value: The value that's retrieved by a get access of the property if the\nproperty is a data property. If this is passed in, set getter, setter,\nmethod and data to NULL (since these members won't be used).getter: A function to call when a get access of the property is performed.\nIf this is passed in, set value and method to NULL (since these members\nwon't be used). The given function is called implicitly by the runtime when the\nproperty is accessed from JavaScript code (or if a get on the property is\nperformed using a N-API call).setter: A function to call when a set access of the property is performed.\nIf this is passed in, set value and method to NULL (since these members\nwon't be used). The given function is called implicitly by the runtime when the\nproperty is set from JavaScript code (or if a set on the property is\nperformed using a N-API call).method: Set this to make the property descriptor object's value\nproperty to be a JavaScript function represented by method. If this is\npassed in, set value, getter and setter to NULL (since these members\nwon't be used).attributes: The attributes associated with the particular property.\nSee napi_property_attributes.data: The callback data passed into method, getter and setter if\nthis function is invoked.napi_status napi_get_property_names(napi_env env,\n napi_value object,\n napi_value* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to retrieve the properties.[out] result: A napi_value representing an array of JavaScript values\nthat represent the property names of the object. The API can be used to\niterate over result using napi_get_array_length\nand napi_get_element.Returns napi_ok if the API succeeded.
This API returns the names of the enumerable properties of object as an array\nof strings. The properties of object whose key is a symbol will not be\nincluded.
napi_status napi_set_property(napi_env env,\n napi_value object,\n napi_value key,\n napi_value value);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object on which to set the property.[in] key: The name of the property to set.[in] value: The property value.Returns napi_ok if the API succeeded.
This API set a property on the Object passed in.
napi_status napi_get_property(napi_env env,\n napi_value object,\n napi_value key,\n napi_value* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to retrieve the property.[in] key: The name of the property to retrieve.[out] result: The value of the property.Returns napi_ok if the API succeeded.
This API gets the requested property from the Object passed in.
napi_status napi_has_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] key: The name of the property whose existence to check.[out] result: Whether the property exists on the object or not.Returns napi_ok if the API succeeded.
This API checks if the Object passed in has the named property.
napi_status napi_delete_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] key: The name of the property to delete.[out] result: Whether the property deletion succeeded or not. result can\noptionally be ignored by passing NULL.Returns napi_ok if the API succeeded.
This API attempts to delete the key own property from object.
napi_status napi_has_own_property(napi_env env,\n napi_value object,\n napi_value key,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] key: The name of the own property whose existence to check.[out] result: Whether the own property exists on the object or not.Returns napi_ok if the API succeeded.
This API checks if the Object passed in has the named own property. key must\nbe a string or a Symbol, or an error will be thrown. N-API will not perform\nany conversion between data types.
napi_status napi_set_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n napi_value value);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object on which to set the property.[in] utf8Name: The name of the property to set.[in] value: The property value.Returns napi_ok if the API succeeded.
This method is equivalent to calling napi_set_property with a napi_value\ncreated from the string passed in as utf8Name.
napi_status napi_get_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n napi_value* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to retrieve the property.[in] utf8Name: The name of the property to get.[out] result: The value of the property.Returns napi_ok if the API succeeded.
This method is equivalent to calling napi_get_property with a napi_value\ncreated from the string passed in as utf8Name.
napi_status napi_has_named_property(napi_env env,\n napi_value object,\n const char* utf8Name,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] utf8Name: The name of the property whose existence to check.[out] result: Whether the property exists on the object or not.Returns napi_ok if the API succeeded.
This method is equivalent to calling napi_has_property with a napi_value\ncreated from the string passed in as utf8Name.
napi_status napi_set_element(napi_env env,\n napi_value object,\n uint32_t index,\n napi_value value);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to set the properties.[in] index: The index of the property to set.[in] value: The property value.Returns napi_ok if the API succeeded.
This API sets and element on the Object passed in.
napi_status napi_get_element(napi_env env,\n napi_value object,\n uint32_t index,\n napi_value* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to retrieve the property.[in] index: The index of the property to get.[out] result: The value of the property.Returns napi_ok if the API succeeded.
This API gets the element at the requested index.
", "type": "module", "displayName": "napi_get_element" }, { "textRaw": "napi_has_element", "name": "napi_has_element", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_has_element(napi_env env,\n napi_value object,\n uint32_t index,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] index: The index of the property whose existence to check.[out] result: Whether the property exists on the object or not.Returns napi_ok if the API succeeded.
This API returns if the Object passed in has an element at the\nrequested index.
napi_status napi_delete_element(napi_env env,\n napi_value object,\n uint32_t index,\n bool* result);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object to query.[in] index: The index of the property to delete.[out] result: Whether the element deletion succeeded or not. result can\noptionally be ignored by passing NULL.Returns napi_ok if the API succeeded.
This API attempts to delete the specified index from object.
napi_status napi_define_properties(napi_env env,\n napi_value object,\n size_t property_count,\n const napi_property_descriptor* properties);\n[in] env: The environment that the N-API call is invoked under.[in] object: The object from which to retrieve the properties.[in] property_count: The number of elements in the properties array.[in] properties: The array of property descriptors.Returns napi_ok if the API succeeded.
This method allows the efficient definition of multiple properties on a given\nobject. The properties are defined using property descriptors (see\nnapi_property_descriptor). Given an array of such property descriptors,\nthis API will set the properties on the object one at a time, as defined by\nDefineOwnProperty() (described in Section 9.1.6 of the ECMA262\nspecification).
N-API provides a set of APIs that allow JavaScript code to\ncall back into native code. N-API APIs that support calling back\ninto native code take in a callback functions represented by\nthe napi_callback type. When the JavaScript VM calls back to\nnative code, the napi_callback function provided is invoked. The APIs\ndocumented in this section allow the callback function to do the\nfollowing:
napi_value back from the callback.Additionally, N-API provides a set of functions which allow calling\nJavaScript functions from native code. One can either call a function\nlike a regular JavaScript function call, or as a constructor\nfunction.
\nAny non-NULL data which is passed to this API via the data field of the\nnapi_property_descriptor items can be associated with object and freed\nwhenever object is garbage-collected by passing both object and the data to\nnapi_add_finalizer.
napi_status napi_call_function(napi_env env,\n napi_value recv,\n napi_value func,\n int argc,\n const napi_value* argv,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] recv: The this object passed to the called function.[in] func: napi_value representing the JavaScript function\nto be invoked.[in] argc: The count of elements in the argv array.[in] argv: Array of napi_values representing JavaScript values passed\nin as arguments to the function.[out] result: napi_value representing the JavaScript object returned.Returns napi_ok if the API succeeded.
This method allows a JavaScript function object to be called from a native\nadd-on. This is the primary mechanism of calling back from the add-on's\nnative code into JavaScript. For the special case of calling into JavaScript\nafter an async operation, see napi_make_callback.
A sample use case might look as follows. Consider the following JavaScript\nsnippet:
\nfunction AddTwo(num) {\n return num + 2;\n}\nThen, the above function can be invoked from a native add-on using the\nfollowing code:
\n// Get the function named \"AddTwo\" on the global object\nnapi_value global, add_two, arg;\nnapi_status status = napi_get_global(env, &global);\nif (status != napi_ok) return;\n\nstatus = napi_get_named_property(env, global, \"AddTwo\", &add_two);\nif (status != napi_ok) return;\n\n// const arg = 1337\nstatus = napi_create_int32(env, 1337, &arg);\nif (status != napi_ok) return;\n\nnapi_value* argv = &arg;\nsize_t argc = 1;\n\n// AddTwo(arg);\nnapi_value return_val;\nstatus = napi_call_function(env, global, add_two, argc, argv, &return_val);\nif (status != napi_ok) return;\n\n// Convert the result back to a native type\nint32_t result;\nstatus = napi_get_value_int32(env, return_val, &result);\nif (status != napi_ok) return;\nnapi_status napi_create_function(napi_env env,\n const char* utf8name,\n size_t length,\n napi_callback cb,\n void* data,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] utf8Name: The name of the function encoded as UTF8. This is visible\nwithin JavaScript as the new function object's name property.[in] length: The length of the utf8name in bytes, or\nNAPI_AUTO_LENGTH if it is null-terminated.[in] cb: The native function which should be called when this function\nobject is invoked.[in] data: User-provided data context. This will be passed back into the\nfunction when invoked later.[out] result: napi_value representing the JavaScript function object for\nthe newly created function.Returns napi_ok if the API succeeded.
This API allows an add-on author to create a function object in native code.\nThis is the primary mechanism to allow calling into the add-on's native code\nfrom JavaScript.
\nThe newly created function is not automatically visible from script after this\ncall. Instead, a property must be explicitly set on any object that is visible\nto JavaScript, in order for the function to be accessible from script.
\nIn order to expose a function as part of the\nadd-on's module exports, set the newly created function on the exports\nobject. A sample module might look as follows:
\nnapi_value SayHello(napi_env env, napi_callback_info info) {\n printf(\"Hello\\n\");\n return NULL;\n}\n\nnapi_value Init(napi_env env, napi_value exports) {\n napi_status status;\n\n napi_value fn;\n status = napi_create_function(env, NULL, 0, SayHello, NULL, &fn);\n if (status != napi_ok) return NULL;\n\n status = napi_set_named_property(env, exports, \"sayHello\", fn);\n if (status != napi_ok) return NULL;\n\n return exports;\n}\n\nNAPI_MODULE(NODE_GYP_MODULE_NAME, Init)\nGiven the above code, the add-on can be used from JavaScript as follows:
\nconst myaddon = require('./addon');\nmyaddon.sayHello();\nThe string passed to require() is the name of the target in binding.gyp\nresponsible for creating the .node file.
Any non-NULL data which is passed to this API via the data parameter can\nbe associated with the resulting JavaScript function (which is returned in the\nresult parameter) and freed whenever the function is garbage-collected by\npassing both the JavaScript function and the data to napi_add_finalizer.
JavaScript Functions are described in\nSection 19.2\nof the ECMAScript Language Specification.
napi_status napi_get_cb_info(napi_env env,\n napi_callback_info cbinfo,\n size_t* argc,\n napi_value* argv,\n napi_value* thisArg,\n void** data)\n[in] env: The environment that the API is invoked under.[in] cbinfo: The callback info passed into the callback function.[in-out] argc: Specifies the size of the provided argv array\nand receives the actual count of arguments.[out] argv: Buffer to which the napi_value representing the\narguments are copied. If there are more arguments than the provided\ncount, only the requested number of arguments are copied. If there are fewer\narguments provided than claimed, the rest of argv is filled with napi_value\nvalues that represent undefined.[out] this: Receives the JavaScript this argument for the call.[out] data: Receives the data pointer for the callback.Returns napi_ok if the API succeeded.
This method is used within a callback function to retrieve details about the\ncall like the arguments and the this pointer from a given callback info.
napi_status napi_get_new_target(napi_env env,\n napi_callback_info cbinfo,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] cbinfo: The callback info passed into the callback function.[out] result: The new.target of the constructor call.Returns napi_ok if the API succeeded.
This API returns the new.target of the constructor call. If the current\ncallback is not a constructor call, the result is NULL.
napi_status napi_new_instance(napi_env env,\n napi_value cons,\n size_t argc,\n napi_value* argv,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] cons: napi_value representing the JavaScript function\nto be invoked as a constructor.[in] argc: The count of elements in the argv array.[in] argv: Array of JavaScript values as napi_value\nrepresenting the arguments to the constructor.[out] result: napi_value representing the JavaScript object returned,\nwhich in this case is the constructed object.This method is used to instantiate a new JavaScript value using a given\nnapi_value that represents the constructor for the object. For example,\nconsider the following snippet:
function MyObject(param) {\n this.param = param;\n}\n\nconst arg = 'hello';\nconst value = new MyObject(arg);\nThe following can be approximated in N-API using the following snippet:
\n// Get the constructor function MyObject\nnapi_value global, constructor, arg, value;\nnapi_status status = napi_get_global(env, &global);\nif (status != napi_ok) return;\n\nstatus = napi_get_named_property(env, global, \"MyObject\", &constructor);\nif (status != napi_ok) return;\n\n// const arg = \"hello\"\nstatus = napi_create_string_utf8(env, \"hello\", NAPI_AUTO_LENGTH, &arg);\nif (status != napi_ok) return;\n\nnapi_value* argv = &arg;\nsize_t argc = 1;\n\n// const value = new MyObject(arg)\nstatus = napi_new_instance(env, constructor, argc, argv, &value);\nReturns napi_ok if the API succeeded.
N-API offers a way to \"wrap\" C++ classes and instances so that the class\nconstructor and methods can be called from JavaScript.
\nnapi_define_class API defines a JavaScript class with constructor,\nstatic properties and methods, and instance properties and methods that\ncorrespond to the C++ class.napi_wrap to wrap a new C++ instance in a JavaScript object,\nthen returns the wrapper object.napi_callback C++ function is invoked. For an instance\ncallback, napi_unwrap obtains the C++ instance that is the target of\nthe call.For wrapped objects it may be difficult to distinguish between a function\ncalled on a class prototype and a function called on an instance of a class.\nA common pattern used to address this problem is to save a persistent\nreference to the class constructor for later instanceof checks.
napi_value MyClass_constructor = NULL;\nstatus = napi_get_reference_value(env, MyClass::es_constructor, &MyClass_constructor);\nassert(napi_ok == status);\nbool is_instance = false;\nstatus = napi_instanceof(env, es_this, MyClass_constructor, &is_instance);\nassert(napi_ok == status);\nif (is_instance) {\n // napi_unwrap() ...\n} else {\n // otherwise...\n}\nThe reference must be freed once it is no longer needed.
", "modules": [ { "textRaw": "napi_define_class", "name": "napi_define_class", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_define_class(napi_env env,\n const char* utf8name,\n size_t length,\n napi_callback constructor,\n void* data,\n size_t property_count,\n const napi_property_descriptor* properties,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] utf8name: Name of the JavaScript constructor function; this is\nnot required to be the same as the C++ class name, though it is recommended\nfor clarity.[in] length: The length of the utf8name in bytes, or NAPI_AUTO_LENGTH\nif it is null-terminated.[in] constructor: Callback function that handles constructing instances\nof the class. (This should be a static method on the class, not an actual\nC++ constructor function.)[in] data: Optional data to be passed to the constructor callback as\nthe data property of the callback info.[in] property_count: Number of items in the properties array argument.[in] properties: Array of property descriptors describing static and\ninstance data properties, accessors, and methods on the class\nSee napi_property_descriptor.[out] result: A napi_value representing the constructor function for\nthe class.Returns napi_ok if the API succeeded.
Defines a JavaScript class that corresponds to a C++ class, including:
\nnapi_static attribute).prototype object corresponding to\nnon-static data properties, accessors, and methods of the C++ class\n(defined by property descriptors without the napi_static attribute).The C++ constructor callback should be a static method on the class that calls\nthe actual class constructor, then wraps the new C++ instance in a JavaScript\nobject, and returns the wrapper object. See napi_wrap() for details.
The JavaScript constructor function returned from napi_define_class is\noften saved and used later, to construct new instances of the class from native\ncode, and/or check whether provided values are instances of the class. In that\ncase, to prevent the function value from being garbage-collected, create a\npersistent reference to it using napi_create_reference and ensure the\nreference count is kept >= 1.
Any non-NULL data which is passed to this API via the data parameter or via\nthe data field of the napi_property_descriptor array items can be associated\nwith the resulting JavaScript constructor (which is returned in the result\nparameter) and freed whenever the class is garbage-collected by passing both\nthe JavaScript function and the data to napi_add_finalizer.
napi_status napi_wrap(napi_env env,\n napi_value js_object,\n void* native_object,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_ref* result);\n[in] env: The environment that the API is invoked under.[in] js_object: The JavaScript object that will be the wrapper for the\nnative object.[in] native_object: The native instance that will be wrapped in the\nJavaScript object.[in] finalize_cb: Optional native callback that can be used to free the\nnative instance when the JavaScript object is ready for garbage-collection.[in] finalize_hint: Optional contextual hint that is passed to the\nfinalize callback.[out] result: Optional reference to the wrapped object.Returns napi_ok if the API succeeded.
Wraps a native instance in a JavaScript object. The native instance can be\nretrieved later using napi_unwrap().
When JavaScript code invokes a constructor for a class that was defined using\nnapi_define_class(), the napi_callback for the constructor is invoked.\nAfter constructing an instance of the native class, the callback must then call\nnapi_wrap() to wrap the newly constructed instance in the already-created\nJavaScript object that is the this argument to the constructor callback.\n(That this object was created from the constructor function's prototype,\nso it already has definitions of all the instance properties and methods.)
Typically when wrapping a class instance, a finalize callback should be\nprovided that simply deletes the native instance that is received as the data\nargument to the finalize callback.
The optional returned reference is initially a weak reference, meaning it\nhas a reference count of 0. Typically this reference count would be incremented\ntemporarily during async operations that require the instance to remain valid.
\nCaution: The optional returned reference (if obtained) should be deleted via\nnapi_delete_reference ONLY in response to the finalize callback\ninvocation. If it is deleted before then, then the finalize callback may never\nbe invoked. Therefore, when obtaining a reference a finalize callback is also\nrequired in order to enable correct disposal of the reference.
Calling napi_wrap() a second time on an object will return an error. To\nassociate another native instance with the object, use napi_remove_wrap()\nfirst.
napi_status napi_unwrap(napi_env env,\n napi_value js_object,\n void** result);\n[in] env: The environment that the API is invoked under.[in] js_object: The object associated with the native instance.[out] result: Pointer to the wrapped native instance.Returns napi_ok if the API succeeded.
Retrieves a native instance that was previously wrapped in a JavaScript\nobject using napi_wrap().
When JavaScript code invokes a method or property accessor on the class, the\ncorresponding napi_callback is invoked. If the callback is for an instance\nmethod or accessor, then the this argument to the callback is the wrapper\nobject; the wrapped C++ instance that is the target of the call can be obtained\nthen by calling napi_unwrap() on the wrapper object.
napi_status napi_remove_wrap(napi_env env,\n napi_value js_object,\n void** result);\n[in] env: The environment that the API is invoked under.[in] js_object: The object associated with the native instance.[out] result: Pointer to the wrapped native instance.Returns napi_ok if the API succeeded.
Retrieves a native instance that was previously wrapped in the JavaScript\nobject js_object using napi_wrap() and removes the wrapping. If a finalize\ncallback was associated with the wrapping, it will no longer be called when the\nJavaScript object becomes garbage-collected.
napi_status napi_add_finalizer(napi_env env,\n napi_value js_object,\n void* native_object,\n napi_finalize finalize_cb,\n void* finalize_hint,\n napi_ref* result);\n[in] env: The environment that the API is invoked under.[in] js_object: The JavaScript object to which the native data will be\nattached.[in] native_object: The native data that will be attached to the JavaScript\nobject.[in] finalize_cb: Native callback that will be used to free the\nnative data when the JavaScript object is ready for garbage-collection.[in] finalize_hint: Optional contextual hint that is passed to the\nfinalize callback.[out] result: Optional reference to the JavaScript object.Returns napi_ok if the API succeeded.
Adds a napi_finalize callback which will be called when the JavaScript object\nin js_object is ready for garbage collection. This API is similar to\nnapi_wrap() except that
napi_unwrap(),napi_remove_wrap(), andCaution: The optional returned reference (if obtained) should be deleted via\nnapi_delete_reference ONLY in response to the finalize callback\ninvocation. If it is deleted before then, then the finalize callback may never\nbe invoked. Therefore, when obtaining a reference a finalize callback is also\nrequired in order to enable correct disposal of the reference.
Addon modules often need to leverage async helpers from libuv as part of their\nimplementation. This allows them to schedule work to be executed asynchronously\nso that their methods can return in advance of the work being completed. This\nis important in order to allow them to avoid blocking overall execution\nof the Node.js application.
\nN-API provides an ABI-stable interface for these\nsupporting functions which covers the most common asynchronous use cases.
\nN-API defines the napi_work structure which is used to manage\nasynchronous workers. Instances are created/deleted with\nnapi_create_async_work and napi_delete_async_work.
The execute and complete callbacks are functions that will be\ninvoked when the executor is ready to execute and when it completes its\ntask respectively.
The execute function should avoid making any N-API calls\nthat could result in the execution of JavaScript or interaction with\nJavaScript objects. Most often, any code that needs to make N-API\ncalls should be made in complete callback instead.
These functions implement the following interfaces:
\ntypedef void (*napi_async_execute_callback)(napi_env env,\n void* data);\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\nWhen these methods are invoked, the data parameter passed will be the\naddon-provided void* data that was passed into the\nnapi_create_async_work call.
Once created the async worker can be queued\nfor execution using the napi_queue_async_work function:
napi_status napi_queue_async_work(napi_env env,\n napi_async_work work);\nnapi_cancel_async_work can be used if the work needs\nto be cancelled before the work has started execution.
After calling napi_cancel_async_work, the complete callback\nwill be invoked with a status value of napi_cancelled.\nThe work should not be deleted before the complete\ncallback invocation, even when it was cancelled.
napi_status napi_create_async_work(napi_env env,\n napi_value async_resource,\n napi_value async_resource_name,\n napi_async_execute_callback execute,\n napi_async_complete_callback complete,\n void* data,\n napi_async_work* result);\n[in] env: The environment that the API is invoked under.[in] async_resource: An optional object associated with the async work\nthat will be passed to possible async_hooks init hooks.[in] async_resource_name: Identifier for the kind of resource that is\nbeing provided for diagnostic information exposed by the async_hooks API.[in] execute: The native function which should be called to execute\nthe logic asynchronously. The given function is called from a worker pool\nthread and can execute in parallel with the main event loop thread.[in] complete: The native function which will be called when the\nasynchronous logic is completed or is cancelled. The given function is called\nfrom the main event loop thread.[in] data: User-provided data context. This will be passed back into the\nexecute and complete functions.[out] result: napi_async_work* which is the handle to the newly created\nasync work.Returns napi_ok if the API succeeded.
This API allocates a work object that is used to execute logic asynchronously.\nIt should be freed using napi_delete_async_work once the work is no longer\nrequired.
async_resource_name should be a null-terminated, UTF-8-encoded string.
The async_resource_name identifier is provided by the user and should be\nrepresentative of the type of async work being performed. It is also recommended\nto apply namespacing to the identifier, e.g. by including the module name. See\nthe async_hooks documentation for more information.
napi_status napi_delete_async_work(napi_env env,\n napi_async_work work);\n[in] env: The environment that the API is invoked under.[in] work: The handle returned by the call to napi_create_async_work.Returns napi_ok if the API succeeded.
This API frees a previously allocated work object.
\nThis API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_delete_async_work" }, { "textRaw": "napi_queue_async_work", "name": "napi_queue_async_work", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_queue_async_work(napi_env env,\n napi_async_work work);\n[in] env: The environment that the API is invoked under.[in] work: The handle returned by the call to napi_create_async_work.Returns napi_ok if the API succeeded.
This API requests that the previously allocated work be scheduled\nfor execution.
", "type": "module", "displayName": "napi_queue_async_work" }, { "textRaw": "napi_cancel_async_work", "name": "napi_cancel_async_work", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_cancel_async_work(napi_env env,\n napi_async_work work);\n[in] env: The environment that the API is invoked under.[in] work: The handle returned by the call to napi_create_async_work.Returns napi_ok if the API succeeded.
This API cancels queued work if it has not yet\nbeen started. If it has already started executing, it cannot be\ncancelled and napi_generic_failure will be returned. If successful,\nthe complete callback will be invoked with a status value of\nnapi_cancelled. The work should not be deleted before the complete\ncallback invocation, even if it has been successfully cancelled.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_cancel_async_work" } ], "type": "misc", "displayName": "Simple Asynchronous Operations" }, { "textRaw": "Custom Asynchronous Operations", "name": "custom_asynchronous_operations", "desc": "The simple asynchronous work APIs above may not be appropriate for every\nscenario. When using any other asynchronous mechanism, the following APIs\nare necessary to ensure an asynchronous operation is properly tracked by\nthe runtime.
", "modules": [ { "textRaw": "napi_async_init", "name": "napi_async_init", "meta": { "added": [ "v8.6.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_async_init(napi_env env,\n napi_value async_resource,\n napi_value async_resource_name,\n napi_async_context* result)\n[in] env: The environment that the API is invoked under.[in] async_resource: An optional object associated with the async work\nthat will be passed to possible async_hooks init hooks.[in] async_resource_name: Identifier for the kind of resource\nthat is being provided for diagnostic information exposed by the\nasync_hooks API.[out] result: The initialized async context.Returns napi_ok if the API succeeded.
napi_status napi_async_destroy(napi_env env,\n napi_async_context async_context);\n[in] env: The environment that the API is invoked under.[in] async_context: The async context to be destroyed.Returns napi_ok if the API succeeded.
This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_async_destroy" }, { "textRaw": "napi_make_callback", "name": "napi_make_callback", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [ { "version": "v8.6.0", "description": "Added `async_context` parameter." } ] }, "desc": "napi_status napi_make_callback(napi_env env,\n napi_async_context async_context,\n napi_value recv,\n napi_value func,\n int argc,\n const napi_value* argv,\n napi_value* result)\n[in] env: The environment that the API is invoked under.[in] async_context: Context for the async operation that is\ninvoking the callback. This should normally be a value previously\nobtained from napi_async_init. However NULL is also allowed,\nwhich indicates the current async context (if any) is to be used\nfor the callback.[in] recv: The this object passed to the called function.[in] func: napi_value representing the JavaScript function\nto be invoked.[in] argc: The count of elements in the argv array.[in] argv: Array of JavaScript values as napi_value\nrepresenting the arguments to the function.[out] result: napi_value representing the JavaScript object returned.Returns napi_ok if the API succeeded.
This method allows a JavaScript function object to be called from a native\nadd-on. This API is similar to napi_call_function. However, it is used to call\nfrom native code back into JavaScript after returning from an async\noperation (when there is no other script on the stack). It is a fairly simple\nwrapper around node::MakeCallback.
Note it is not necessary to use napi_make_callback from within a\nnapi_async_complete_callback; in that situation the callback's async\ncontext has already been set up, so a direct call to napi_call_function\nis sufficient and appropriate. Use of the napi_make_callback function\nmay be required when implementing custom async behavior that does not use\nnapi_create_async_work.
NAPI_EXTERN napi_status napi_open_callback_scope(napi_env env,\n napi_value resource_object,\n napi_async_context context,\n napi_callback_scope* result)\n[in] env: The environment that the API is invoked under.[in] resource_object: An object associated with the async work\nthat will be passed to possible async_hooks init hooks.[in] context: Context for the async operation that is\ninvoking the callback. This should be a value previously obtained\nfrom napi_async_init.[out] result: The newly created scope.There are cases (for example, resolving promises) where it is\nnecessary to have the equivalent of the scope associated with a callback\nin place when making certain N-API calls. If there is no other script on\nthe stack the napi_open_callback_scope and\nnapi_close_callback_scope functions can be used to open/close\nthe required scope.
NAPI_EXTERN napi_status napi_close_callback_scope(napi_env env,\n napi_callback_scope scope)\n[in] env: The environment that the API is invoked under.[in] scope: The scope to be closed.This API can be called even if there is a pending JavaScript exception.
", "type": "module", "displayName": "napi_close_callback_scope" } ], "type": "misc", "displayName": "Custom Asynchronous Operations" }, { "textRaw": "Version Management", "name": "version_management", "modules": [ { "textRaw": "napi_get_node_version", "name": "napi_get_node_version", "meta": { "added": [ "v8.4.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "typedef struct {\n uint32_t major;\n uint32_t minor;\n uint32_t patch;\n const char* release;\n} napi_node_version;\n\nnapi_status napi_get_node_version(napi_env env,\n const napi_node_version** version);\n[in] env: The environment that the API is invoked under.[out] version: A pointer to version information for Node.js itself.Returns napi_ok if the API succeeded.
This function fills the version struct with the major, minor, and patch\nversion of Node.js that is currently running, and the release field with the\nvalue of process.release.name.
The returned buffer is statically allocated and does not need to be freed.
", "type": "module", "displayName": "napi_get_node_version" }, { "textRaw": "napi_get_version", "name": "napi_get_version", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_get_version(napi_env env,\n uint32_t* result);\n[in] env: The environment that the API is invoked under.[out] result: The highest version of N-API supported.Returns napi_ok if the API succeeded.
This API returns the highest N-API version supported by the\nNode.js runtime. N-API is planned to be additive such that\nnewer releases of Node.js may support additional API functions.\nIn order to allow an addon to use a newer function when running with\nversions of Node.js that support it, while providing\nfallback behavior when running with Node.js versions that don't\nsupport it:
\nnapi_get_version() to determine if the API is available.uv_dlsym().NAPI_EXTERN napi_status napi_adjust_external_memory(napi_env env,\n int64_t change_in_bytes,\n int64_t* result);\n[in] env: The environment that the API is invoked under.[in] change_in_bytes: The change in externally allocated memory that is\nkept alive by JavaScript objects.[out] result: The adjusted valueReturns napi_ok if the API succeeded.
This function gives V8 an indication of the amount of externally allocated\nmemory that is kept alive by JavaScript objects (i.e. a JavaScript object\nthat points to its own memory allocated by a native module). Registering\nexternally allocated memory will trigger global garbage collections more\noften than it would otherwise.
\n\n", "type": "module", "displayName": "napi_adjust_external_memory" } ], "type": "misc", "displayName": "Memory Management" }, { "textRaw": "Promises", "name": "promises", "desc": "N-API provides facilities for creating Promise objects as described in\nSection 25.4 of the ECMA specification. It implements promises as a pair of\nobjects. When a promise is created by napi_create_promise(), a \"deferred\"\nobject is created and returned alongside the Promise. The deferred object is\nbound to the created Promise and is the only means to resolve or reject the\nPromise using napi_resolve_deferred() or napi_reject_deferred(). The\ndeferred object that is created by napi_create_promise() is freed by\nnapi_resolve_deferred() or napi_reject_deferred(). The Promise object may\nbe returned to JavaScript where it can be used in the usual fashion.
For example, to create a promise and pass it to an asynchronous worker:
\nnapi_deferred deferred;\nnapi_value promise;\nnapi_status status;\n\n// Create the promise.\nstatus = napi_create_promise(env, &deferred, &promise);\nif (status != napi_ok) return NULL;\n\n// Pass the deferred to a function that performs an asynchronous action.\ndo_something_asynchronous(deferred);\n\n// Return the promise to JS\nreturn promise;\nThe above function do_something_asynchronous() would perform its asynchronous\naction and then it would resolve or reject the deferred, thereby concluding the\npromise and freeing the deferred:
napi_deferred deferred;\nnapi_value undefined;\nnapi_status status;\n\n// Create a value with which to conclude the deferred.\nstatus = napi_get_undefined(env, &undefined);\nif (status != napi_ok) return NULL;\n\n// Resolve or reject the promise associated with the deferred depending on\n// whether the asynchronous action succeeded.\nif (asynchronous_action_succeeded) {\n status = napi_resolve_deferred(env, deferred, undefined);\n} else {\n status = napi_reject_deferred(env, deferred, undefined);\n}\nif (status != napi_ok) return NULL;\n\n// At this point the deferred has been freed, so we should assign NULL to it.\ndeferred = NULL;\nnapi_status napi_create_promise(napi_env env,\n napi_deferred* deferred,\n napi_value* promise);\n[in] env: The environment that the API is invoked under.[out] deferred: A newly created deferred object which can later be passed to\nnapi_resolve_deferred() or napi_reject_deferred() to resolve resp. reject\nthe associated promise.[out] promise: The JavaScript promise associated with the deferred object.Returns napi_ok if the API succeeded.
This API creates a deferred object and a JavaScript promise.
", "type": "module", "displayName": "napi_create_promise" }, { "textRaw": "napi_resolve_deferred", "name": "napi_resolve_deferred", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_resolve_deferred(napi_env env,\n napi_deferred deferred,\n napi_value resolution);\n[in] env: The environment that the API is invoked under.[in] deferred: The deferred object whose associated promise to resolve.[in] resolution: The value with which to resolve the promise.This API resolves a JavaScript promise by way of the deferred object\nwith which it is associated. Thus, it can only be used to resolve JavaScript\npromises for which the corresponding deferred object is available. This\neffectively means that the promise must have been created using\nnapi_create_promise() and the deferred object returned from that call must\nhave been retained in order to be passed to this API.
The deferred object is freed upon successful completion.
", "type": "module", "displayName": "napi_resolve_deferred" }, { "textRaw": "napi_reject_deferred", "name": "napi_reject_deferred", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_reject_deferred(napi_env env,\n napi_deferred deferred,\n napi_value rejection);\n[in] env: The environment that the API is invoked under.[in] deferred: The deferred object whose associated promise to resolve.[in] rejection: The value with which to reject the promise.This API rejects a JavaScript promise by way of the deferred object\nwith which it is associated. Thus, it can only be used to reject JavaScript\npromises for which the corresponding deferred object is available. This\neffectively means that the promise must have been created using\nnapi_create_promise() and the deferred object returned from that call must\nhave been retained in order to be passed to this API.
The deferred object is freed upon successful completion.
", "type": "module", "displayName": "napi_reject_deferred" }, { "textRaw": "napi_is_promise", "name": "napi_is_promise", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "napi_status napi_is_promise(napi_env env,\n napi_value promise,\n bool* is_promise);\n[in] env: The environment that the API is invoked under.[in] promise: The promise to examine[out] is_promise: Flag indicating whether promise is a native promise\nobject - that is, a promise object created by the underlying engine.N-API provides an API for executing a string containing JavaScript using the\nunderlying JavaScript engine.
", "modules": [ { "textRaw": "napi_run_script", "name": "napi_run_script", "meta": { "added": [ "v8.5.0" ], "napiVersion": [ 1 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status napi_run_script(napi_env env,\n napi_value script,\n napi_value* result);\n[in] env: The environment that the API is invoked under.[in] script: A JavaScript string containing the script to execute.[out] result: The value resulting from having executed the script.N-API provides a function for getting the current event loop associated with\na specific napi_env.
NAPI_EXTERN napi_status napi_get_uv_event_loop(napi_env env,\n uv_loop_t** loop);\n[in] env: The environment that the API is invoked under.[out] loop: The current libuv loop instance.JavaScript functions can normally only be called from a native addon's main\nthread. If an addon creates additional threads, then N-API functions that\nrequire a napi_env, napi_value, or napi_ref must not be called from those\nthreads.
When an addon has additional threads and JavaScript functions need to be invoked\nbased on the processing completed by those threads, those threads must\ncommunicate with the addon's main thread so that the main thread can invoke the\nJavaScript function on their behalf. The thread-safe function APIs provide an\neasy way to do this.
\nThese APIs provide the type napi_threadsafe_function as well as APIs to\ncreate, destroy, and call objects of this type.\nnapi_create_threadsafe_function() creates a persistent reference to a\nnapi_value that holds a JavaScript function which can be called from multiple\nthreads. The calls happen asynchronously. This means that values with which the\nJavaScript callback is to be called will be placed in a queue, and, for each\nvalue in the queue, a call will eventually be made to the JavaScript function.
Upon creation of a napi_threadsafe_function a napi_finalize callback can be\nprovided. This callback will be invoked on the main thread when the thread-safe\nfunction is about to be destroyed. It receives the context and the finalize data\ngiven during construction, and provides an opportunity for cleaning up after the\nthreads e.g. by calling uv_thread_join(). It is important that, aside from\nthe main loop thread, there be no threads left using the thread-safe function\nafter the finalize callback completes.
The context given during the call to napi_create_threadsafe_function() can\nbe retrieved from any thread with a call to\nnapi_get_threadsafe_function_context().
napi_call_threadsafe_function() can then be used for initiating a call into\nJavaScript. napi_call_threadsafe_function() accepts a parameter which controls\nwhether the API behaves blockingly. If set to napi_tsfn_nonblocking, the API\nbehaves non-blockingly, returning napi_queue_full if the queue was full,\npreventing data from being successfully added to the queue. If set to\nnapi_tsfn_blocking, the API blocks until space becomes available in the queue.\nnapi_call_threadsafe_function() never blocks if the thread-safe function was\ncreated with a maximum queue size of 0.
The actual call into JavaScript is controlled by the callback given via the\ncall_js_cb parameter. call_js_cb is invoked on the main thread once for each\nvalue that was placed into the queue by a successful call to\nnapi_call_threadsafe_function(). If such a callback is not given, a default\ncallback will be used, and the resulting JavaScript call will have no arguments.\nThe call_js_cb callback receives the JavaScript function to call as a\nnapi_value in its parameters, as well as the void* context pointer used when\ncreating the napi_threadsafe_function, and the next data pointer that was\ncreated by one of the secondary threads. The callback can then use an API such\nas napi_call_function() to call into JavaScript.
The callback may also be invoked with env and call_js_cb both set to NULL\nto indicate that calls into JavaScript are no longer possible, while items\nremain in the queue that may need to be freed. This normally occurs when the\nNode.js process exits while there is a thread-safe function still active.
It is not necessary to call into JavaScript via napi_make_callback() because\nN-API runs call_js_cb in a context appropriate for callbacks.
Threads can be added to and removed from a napi_threadsafe_function object\nduring its existence. Thus, in addition to specifying an initial number of\nthreads upon creation, napi_acquire_threadsafe_function can be called to\nindicate that a new thread will start making use of the thread-safe function.\nSimilarly, napi_release_threadsafe_function can be called to indicate that an\nexisting thread will stop making use of the thread-safe function.
napi_threadsafe_function objects are destroyed when every thread which uses\nthe object has called napi_release_threadsafe_function() or has received a\nreturn status of napi_closing in response to a call to\nnapi_call_threadsafe_function. The queue is emptied before the\nnapi_threadsafe_function is destroyed. It is important that\nnapi_release_threadsafe_function() be the last API call made in conjunction\nwith a given napi_threadsafe_function, because after the call completes, there\nis no guarantee that the napi_threadsafe_function is still allocated. For the\nsame reason it is also important that no more use be made of a thread-safe\nfunction after receiving a return value of napi_closing in response to a call\nto napi_call_threadsafe_function. Data associated with the\nnapi_threadsafe_function can be freed in its napi_finalize callback which\nwas passed to napi_create_threadsafe_function().
Once the number of threads making use of a napi_threadsafe_function reaches\nzero, no further threads can start making use of it by calling\nnapi_acquire_threadsafe_function(). In fact, all subsequent API calls\nassociated with it, except napi_release_threadsafe_function(), will return an\nerror value of napi_closing.
The thread-safe function can be \"aborted\" by giving a value of napi_tsfn_abort\nto napi_release_threadsafe_function(). This will cause all subsequent APIs\nassociated with the thread-safe function except\nnapi_release_threadsafe_function() to return napi_closing even before its\nreference count reaches zero. In particular, napi_call_threadsafe_function()\nwill return napi_closing, thus informing the threads that it is no longer\npossible to make asynchronous calls to the thread-safe function. This can be\nused as a criterion for terminating the thread. Upon receiving a return value\nof napi_closing from napi_call_threadsafe_function() a thread must make no\nfurther use of the thread-safe function because it is no longer guaranteed to\nbe allocated.
Similarly to libuv handles, thread-safe functions can be \"referenced\" and\n\"unreferenced\". A \"referenced\" thread-safe function will cause the event loop on\nthe thread on which it is created to remain alive until the thread-safe function\nis destroyed. In contrast, an \"unreferenced\" thread-safe function will not\nprevent the event loop from exiting. The APIs napi_ref_threadsafe_function and\nnapi_unref_threadsafe_function exist for this purpose.
NAPI_EXTERN napi_status\nnapi_create_threadsafe_function(napi_env env,\n napi_value func,\n napi_value async_resource,\n napi_value async_resource_name,\n size_t max_queue_size,\n size_t initial_thread_count,\n void* thread_finalize_data,\n napi_finalize thread_finalize_cb,\n void* context,\n napi_threadsafe_function_call_js call_js_cb,\n napi_threadsafe_function* result);\n[in] env: The environment that the API is invoked under.[in] func: An optional JavaScript function to call from another thread.\nIt must be provided if NULL is passed to call_js_cb.[in] async_resource: An optional object associated with the async work that\nwill be passed to possible async_hooks init hooks.[in] async_resource_name: A JavaScript string to provide an identifier for\nthe kind of resource that is being provided for diagnostic information exposed\nby the async_hooks API.[in] max_queue_size: Maximum size of the queue. 0 for no limit.[in] initial_thread_count: The initial number of threads, including the main\nthread, which will be making use of this function.[in] thread_finalize_data: Optional data to be passed to thread_finalize_cb.[in] thread_finalize_cb: Optional function to call when the\nnapi_threadsafe_function is being destroyed.[in] context: Optional data to attach to the resulting\nnapi_threadsafe_function.[in] call_js_cb: Optional callback which calls the JavaScript function in\nresponse to a call on a different thread. This callback will be called on the\nmain thread. If not given, the JavaScript function will be called with no\nparameters and with undefined as its this value.[out] result: The asynchronous thread-safe JavaScript function.NAPI_EXTERN napi_status\nnapi_get_threadsafe_function_context(napi_threadsafe_function func,\n void** result);\n[in] func: The thread-safe function for which to retrieve the context.[out] result: The location where to store the context.This API may be called from any thread which makes use of func.
NAPI_EXTERN napi_status\nnapi_call_threadsafe_function(napi_threadsafe_function func,\n void* data,\n napi_threadsafe_function_call_mode is_blocking);\n[in] func: The asynchronous thread-safe JavaScript function to invoke.[in] data: Data to send into JavaScript via the callback call_js_cb\nprovided during the creation of the thread-safe JavaScript function.[in] is_blocking: Flag whose value can be either napi_tsfn_blocking to\nindicate that the call should block if the queue is full or\nnapi_tsfn_nonblocking to indicate that the call should return immediately with\na status of napi_queue_full whenever the queue is full.This API will return napi_closing if napi_release_threadsafe_function() was\ncalled with abort set to napi_tsfn_abort from any thread. The value is only\nadded to the queue if the API returns napi_ok.
This API may be called from any thread which makes use of func.
NAPI_EXTERN napi_status\nnapi_acquire_threadsafe_function(napi_threadsafe_function func);\n[in] func: The asynchronous thread-safe JavaScript function to start making\nuse of.A thread should call this API before passing func to any other thread-safe\nfunction APIs to indicate that it will be making use of func. This prevents\nfunc from being destroyed when all other threads have stopped making use of\nit.
This API may be called from any thread which will start making use of func.
NAPI_EXTERN napi_status\nnapi_release_threadsafe_function(napi_threadsafe_function func,\n napi_threadsafe_function_release_mode mode);\n[in] func: The asynchronous thread-safe JavaScript function whose reference\ncount to decrement.[in] mode: Flag whose value can be either napi_tsfn_release to indicate\nthat the current thread will make no further calls to the thread-safe function,\nor napi_tsfn_abort to indicate that in addition to the current thread, no\nother thread should make any further calls to the thread-safe function. If set\nto napi_tsfn_abort, further calls to napi_call_threadsafe_function() will\nreturn napi_closing, and no further values will be placed in the queue.A thread should call this API when it stops making use of func. Passing func\nto any thread-safe APIs after having called this API has undefined results, as\nfunc may have been destroyed.
This API may be called from any thread which will stop making use of func.
NAPI_EXTERN napi_status\nnapi_ref_threadsafe_function(napi_env env, napi_threadsafe_function func);\n[in] env: The environment that the API is invoked under.[in] func: The thread-safe function to reference.This API is used to indicate that the event loop running on the main thread\nshould not exit until func has been destroyed. Similar to uv_ref it is\nalso idempotent.
This API may only be called from the main thread.
", "type": "module", "displayName": "napi_ref_threadsafe_function" }, { "textRaw": "napi_unref_threadsafe_function", "name": "napi_unref_threadsafe_function", "stability": 2, "stabilityText": "Stable", "meta": { "added": [ "v10.6.0" ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\nnapi_unref_threadsafe_function(napi_env env, napi_threadsafe_function func);\n[in] env: The environment that the API is invoked under.[in] func: The thread-safe function to unreference.This API is used to indicate that the event loop running on the main thread\nmay exit before func is destroyed. Similar to uv_unref it is also\nidempotent.
This API may only be called from the main thread.
", "type": "module", "displayName": "napi_unref_threadsafe_function" } ], "type": "misc", "displayName": "Asynchronous Thread-safe Function Calls" } ] }, { "textRaw": "Command Line Options", "name": "Command Line Options", "introduced_in": "v5.9.1", "type": "misc", "desc": "Node.js comes with a variety of CLI options. These options expose built-in\ndebugging, multiple ways to execute scripts, and other helpful runtime options.
\nTo view this documentation as a manual page in a terminal, run man node.
node [options] [V8 options] [script.js | -e \"script\" | -] [--] [arguments]
node inspect [script.js | -e \"script\" | <host>:<port>] …
node --v8-options
Execute without arguments to start the REPL.
\nFor more info about node inspect, please see the debugger documentation.
All options, including V8 options, allow words to be separated by both\ndashes (-) or underscores (_).
For example, --pending-deprecation is equivalent to --pending_deprecation.
Alias for stdin, analogous to the use of - in other command line utilities,\nmeaning that the script will be read from stdin, and the rest of the options\nare passed to that script.
", "type": "module", "displayName": "`-`" }, { "textRaw": "`--`", "name": "`--`", "meta": { "added": [ "v6.11.0" ], "changes": [] }, "desc": "Indicate the end of node options. Pass the rest of the arguments to the script.\nIf no script filename or eval/print script is supplied prior to this, then\nthe next argument will be used as a script filename.
", "type": "module", "displayName": "`--`" }, { "textRaw": "`--abort-on-uncaught-exception`", "name": "`--abort-on-uncaught-exception`", "meta": { "added": [ "v0.10" ], "changes": [] }, "desc": "Aborting instead of exiting causes a core file to be generated for post-mortem\nanalysis using a debugger (such as lldb, gdb, and mdb).
If this flag is passed, the behavior can still be set to not abort through\nprocess.setUncaughtExceptionCaptureCallback() (and through usage of the\ndomain module that uses it).
Print source-able bash completion script for Node.js.
\n$ node --completion-bash > node_bash_completion\n$ source node_bash_completion\nEnable FIPS-compliant crypto at startup. (Requires Node.js to be built with\n./configure --openssl-fips.)
Enable experimental ES module support and caching modules.
", "type": "module", "displayName": "`--experimental-modules`" }, { "textRaw": "`--experimental-repl-await`", "name": "`--experimental-repl-await`", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "desc": "Enable experimental top-level await keyword support in REPL.
Enable experimental ES Module support in the vm module.
Enable experimental worker threads using the worker_threads module.
Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.)\n(Same requirements as --enable-fips.)
Specify ICU data load path. (Overrides NODE_ICU_DATA.)
Activate inspector on host:port and break at start of user script.\nDefault host:port is 127.0.0.1:9229.
Set the host:port to be used when the inspector is activated.\nUseful when activating the inspector by sending the SIGUSR1 signal.
Default host is 127.0.0.1.
See the security warning below regarding the host\nparameter usage.
Activate inspector on host:port. Default is 127.0.0.1:9229.
V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug\nand profile Node.js instances. The tools attach to Node.js instances via a\ntcp port and communicate using the Chrome DevTools Protocol.
\n", "modules": [ { "textRaw": "Warning: binding inspector to a public IP:port combination is insecure", "name": "warning:_binding_inspector_to_a_public_ip:port_combination_is_insecure", "desc": "Binding the inspector to a public IP (including 0.0.0.0) with an open port is\ninsecure, as it allows external hosts to connect to the inspector and perform\na remote code execution attack.
If you specify a host, make sure that at least one of the following is true:\neither the host is not public, or the port is properly firewalled to disallow\nunwanted connections.
\nMore specifically, --inspect=0.0.0.0 is insecure if the port (9229 by\ndefault) is not firewall-protected.
See the debugging security implications section for more information.
", "type": "module", "displayName": "Warning: binding inspector to a public IP:port combination is insecure" } ], "type": "module", "displayName": "`--inspect[=[host:]port]`" }, { "textRaw": "`--loader=file`", "name": "`--loader=file`", "meta": { "added": [ "v9.0.0" ], "changes": [] }, "desc": "Specify the file of the custom experimental ECMAScript Module loader.
Use an insecure HTTP parser that accepts invalid HTTP headers. This may allow\ninteroperability with non-conformant HTTP implementations. It may also allow\nrequest smuggling and other HTTP attacks that rely on invalid headers being\naccepted. Avoid using this option.
", "type": "module", "displayName": "`--insecure-http-parser`" }, { "textRaw": "`--max-http-header-size=size`", "name": "`--max-http-header-size=size`", "meta": { "added": [ "v10.15.0" ], "changes": [] }, "desc": "Specify the maximum size, in bytes, of HTTP headers. Defaults to 8KB.
", "type": "module", "displayName": "`--max-http-header-size=size`" }, { "textRaw": "`--napi-modules`", "name": "`--napi-modules`", "meta": { "added": [ "v7.10.0" ], "changes": [] }, "desc": "This option is a no-op. It is kept for compatibility.
", "type": "module", "displayName": "`--napi-modules`" }, { "textRaw": "`--no-deprecation`", "name": "`--no-deprecation`", "meta": { "added": [ "v0.8.0" ], "changes": [] }, "desc": "Silence deprecation warnings.
", "type": "module", "displayName": "`--no-deprecation`" }, { "textRaw": "`--no-force-async-hooks-checks`", "name": "`--no-force-async-hooks-checks`", "meta": { "added": [ "v9.0.0" ], "changes": [] }, "desc": "Disables runtime checks for async_hooks. These will still be enabled\ndynamically when async_hooks is enabled.
Silence all process warnings (including deprecations).
", "type": "module", "displayName": "`--no-warnings`" }, { "textRaw": "`--openssl-config=file`", "name": "`--openssl-config=file`", "meta": { "added": [ "v6.9.0" ], "changes": [] }, "desc": "Load an OpenSSL configuration file on startup. Among other uses, this can be\nused to enable FIPS-compliant crypto if Node.js is built with\n./configure --openssl-fips.
Emit pending deprecation warnings.
\nPending deprecations are generally identical to a runtime deprecation with the\nnotable exception that they are turned off by default and will not be emitted\nunless either the --pending-deprecation command line flag, or the\nNODE_PENDING_DEPRECATION=1 environment variable, is set. Pending deprecations\nare used to provide a kind of selective \"early warning\" mechanism that\ndevelopers may leverage to detect deprecated API usage.
Instructs the module loader to preserve symbolic links when resolving and\ncaching modules.
\nBy default, when Node.js loads a module from a path that is symbolically linked\nto a different on-disk location, Node.js will dereference the link and use the\nactual on-disk \"real path\" of the module as both an identifier and as a root\npath to locate other dependency modules. In most cases, this default behavior\nis acceptable. However, when using symbolically linked peer dependencies, as\nillustrated in the example below, the default behavior causes an exception to\nbe thrown if moduleA attempts to require moduleB as a peer dependency:
{appDir}\n ├── app\n │ ├── index.js\n │ └── node_modules\n │ ├── moduleA -> {appDir}/moduleA\n │ └── moduleB\n │ ├── index.js\n │ └── package.json\n └── moduleA\n ├── index.js\n └── package.json\nThe --preserve-symlinks command line flag instructs Node.js to use the\nsymlink path for modules as opposed to the real path, allowing symbolically\nlinked peer dependencies to be found.
Note, however, that using --preserve-symlinks can have other side effects.\nSpecifically, symbolically linked native modules can fail to load if those\nare linked from more than one location in the dependency tree (Node.js would\nsee those as two separate modules and would attempt to load the module multiple\ntimes, causing an exception to be thrown).
The --preserve-symlinks flag does not apply to the main module, which allows\nnode --preserve-symlinks node_module/.bin/<foo> to work. To apply the same\nbehavior for the main module, also use --preserve-symlinks-main.
Instructs the module loader to preserve symbolic links when resolving and\ncaching the main module (require.main).
This flag exists so that the main module can be opted-in to the same behavior\nthat --preserve-symlinks gives to all other imports; they are separate flags,\nhowever, for backward compatibility with older Node.js versions.
Note that --preserve-symlinks-main does not imply --preserve-symlinks; it\nis expected that --preserve-symlinks-main will be used in addition to\n--preserve-symlinks when it is not desirable to follow symlinks before\nresolving relative paths.
See --preserve-symlinks for more information.
Generate V8 profiler output.
", "type": "module", "displayName": "`--prof`" }, { "textRaw": "`--prof-process`", "name": "`--prof-process`", "meta": { "added": [ "v5.2.0" ], "changes": [] }, "desc": "Process V8 profiler output generated using the V8 option --prof.
Write process warnings to the given file instead of printing to stderr. The\nfile will be created if it does not exist, and will be appended to if it does.\nIf an error occurs while attempting to write the warning to the file, the\nwarning will be written to stderr instead.
", "type": "module", "displayName": "`--redirect-warnings=file`" }, { "textRaw": "`--throw-deprecation`", "name": "`--throw-deprecation`", "meta": { "added": [ "v0.11.14" ], "changes": [] }, "desc": "Throw errors for deprecations.
", "type": "module", "displayName": "`--throw-deprecation`" }, { "textRaw": "`--title=title`", "name": "`--title=title`", "meta": { "added": [ "v10.7.0" ], "changes": [] }, "desc": "Set process.title on startup.
Specify an alternative default TLS cipher list. Requires Node.js to be built\nwith crypto support (default).
", "type": "module", "displayName": "`--tls-cipher-list=list`" }, { "textRaw": "`--trace-deprecation`", "name": "`--trace-deprecation`", "meta": { "added": [ "v0.8.0" ], "changes": [] }, "desc": "Print stack traces for deprecations.
", "type": "module", "displayName": "`--trace-deprecation`" }, { "textRaw": "`--trace-event-categories`", "name": "`--trace-event-categories`", "meta": { "added": [ "v7.7.0" ], "changes": [] }, "desc": "A comma separated list of categories that should be traced when trace event\ntracing is enabled using --trace-events-enabled.
Template string specifying the filepath for the trace event data, it\nsupports ${rotation} and ${pid}.
Enables the collection of trace event tracing information.
", "type": "module", "displayName": "`--trace-events-enabled`" }, { "textRaw": "`--trace-sync-io`", "name": "`--trace-sync-io`", "meta": { "added": [ "v2.1.0" ], "changes": [] }, "desc": "Prints a stack trace whenever synchronous I/O is detected after the first turn\nof the event loop.
", "type": "module", "displayName": "`--trace-sync-io`" }, { "textRaw": "`--trace-warnings`", "name": "`--trace-warnings`", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "desc": "Print stack traces for process warnings (including deprecations).
", "type": "module", "displayName": "`--trace-warnings`" }, { "textRaw": "`--track-heap-objects`", "name": "`--track-heap-objects`", "meta": { "added": [ "v2.4.0" ], "changes": [] }, "desc": "Track heap object allocations for heap snapshots.
", "type": "module", "displayName": "`--track-heap-objects`" }, { "textRaw": "`--unhandled-rejections=mode`", "name": "`--unhandled-rejections=mode`", "meta": { "added": [ "v10.17.0" ], "changes": [] }, "desc": "By default all unhandled rejections trigger a warning plus a deprecation warning\nfor the very first unhandled rejection in case no unhandledRejection hook\nis used.
Using this flag allows to change what should happen when an unhandled rejection\noccurs. One of three modes can be chosen:
\nstrict: Raise the unhandled rejection as an uncaught exception.warn: Always trigger a warning, no matter if the unhandledRejection\nhook is set or not but do not print the deprecation warning.none: Silence all warnings.Use bundled Mozilla CA store as supplied by current Node.js version\nor use OpenSSL's default CA store. The default store is selectable\nat build-time.
\nThe bundled CA store, as supplied by Node.js, is a snapshot of Mozilla CA store\nthat is fixed at release time. It is identical on all supported platforms.
\nUsing OpenSSL store allows for external modifications of the store. For most\nLinux and BSD distributions, this store is maintained by the distribution\nmaintainers and system administrators. OpenSSL CA store location is dependent on\nconfiguration of the OpenSSL library but this can be altered at runtime using\nenvironment variables.
\nSee SSL_CERT_DIR and SSL_CERT_FILE.
Print V8 command line options.
", "type": "module", "displayName": "`--v8-options`" }, { "textRaw": "`--v8-pool-size=num`", "name": "`--v8-pool-size=num`", "meta": { "added": [ "v5.10.0" ], "changes": [] }, "desc": "Set V8's thread pool size which will be used to allocate background jobs.
\nIf set to 0 then V8 will choose an appropriate size of the thread pool based\non the number of online processors.
If the value provided is larger than V8's maximum, then the largest value\nwill be chosen.
", "type": "module", "displayName": "`--v8-pool-size=num`" }, { "textRaw": "`--zero-fill-buffers`", "name": "`--zero-fill-buffers`", "meta": { "added": [ "v6.0.0" ], "changes": [] }, "desc": "Automatically zero-fills all newly allocated Buffer and SlowBuffer\ninstances.
Syntax check the script without executing.
", "type": "module", "displayName": "`-c`, `--check`" }, { "textRaw": "`-e`, `--eval \"script\"`", "name": "`-e`,_`--eval_\"script\"`", "meta": { "added": [ "v0.5.2" ], "changes": [ { "version": "v5.11.0", "pr-url": "https://github.com/nodejs/node/pull/5348", "description": "Built-in libraries are now available as predefined variables." } ] }, "desc": "Evaluate the following argument as JavaScript. The modules which are\npredefined in the REPL can also be used in script.
On Windows, using cmd.exe a single quote will not work correctly because it\nonly recognizes double \" for quoting. In Powershell or Git bash, both '\nand \" are usable.
Print node command line options.\nThe output of this option is less detailed than this document.
", "type": "module", "displayName": "`-h`, `--help`" }, { "textRaw": "`-i`, `--interactive`", "name": "`-i`,_`--interactive`", "meta": { "added": [ "v0.7.7" ], "changes": [] }, "desc": "Opens the REPL even if stdin does not appear to be a terminal.
", "type": "module", "displayName": "`-i`, `--interactive`" }, { "textRaw": "`-p`, `--print \"script\"`", "name": "`-p`,_`--print_\"script\"`", "meta": { "added": [ "v0.6.4" ], "changes": [ { "version": "v5.11.0", "pr-url": "https://github.com/nodejs/node/pull/5348", "description": "Built-in libraries are now available as predefined variables." } ] }, "desc": "Identical to -e but prints the result.
Preload the specified module at startup.
\nFollows require()'s module resolution\nrules. module may be either a path to a file, or a node module name.
Print node's version.
", "type": "module", "displayName": "`-v`, `--version`" } ], "type": "misc", "displayName": "Options" }, { "textRaw": "Environment Variables", "name": "environment_variables", "modules": [ { "textRaw": "`NODE_DEBUG=module[,…]`", "name": "`node_debug=module[,…]`", "meta": { "added": [ "v0.1.32" ], "changes": [] }, "desc": "','-separated list of core modules that should print debug information.
','-separated list of core C++ modules that should print debug information.
When set to 1 colors will not be used in the REPL.
When set, the well known \"root\" CAs (like VeriSign) will be extended with the\nextra certificates in file. The file should consist of one or more trusted\ncertificates in PEM format. A message will be emitted (once) with\nprocess.emitWarning() if the file is missing or\nmalformed, but any errors are otherwise ignored.
Note that neither the well known nor extra certificates are used when the ca\noptions property is explicitly specified for a TLS or HTTPS client or server.
This environment variable is ignored when node runs as setuid root or\nhas Linux file capabilities set.
Data path for ICU (Intl object) data. Will extend linked-in data when compiled\nwith small-icu support.
When set to 1, process warnings are silenced.
A space-separated list of command line options. options... are interpreted as\nif they had been specified on the command line before the actual command line\n(so they can be overridden). Node.js will exit with an error if an option\nthat is not allowed in the environment is used, such as -p or a script file.
Node.js options that are allowed are:
\n--enable-fips--experimental-modules--experimental-repl-await--experimental-vm-modules--experimental-worker--force-fips--icu-data-dir--insecure-http-parser--inspect--inspect-brk--inspect-port--loader--max-http-header-size--napi-modules--no-deprecation--no-force-async-hooks-checks--no-warnings--openssl-config--pending-deprecation--redirect-warnings--require, -r--throw-deprecation--title--tls-cipher-list--trace-deprecation--trace-event-categories--trace-event-file-pattern--trace-events-enabled--trace-sync-io--trace-warnings--track-heap-objects--unhandled-rejections--use-bundled-ca--use-openssl-ca--v8-pool-size--zero-fill-buffersV8 options that are allowed are:
\n--abort-on-uncaught-exception--max-old-space-size--perf-basic-prof--perf-prof--stack-trace-limit':'-separated list of directories prefixed to the module search path.
On Windows, this is a ';'-separated list instead.
When set to 1, emit pending deprecation warnings.
Pending deprecations are generally identical to a runtime deprecation with the\nnotable exception that they are turned off by default and will not be emitted\nunless either the --pending-deprecation command line flag, or the\nNODE_PENDING_DEPRECATION=1 environment variable, is set. Pending deprecations\nare used to provide a kind of selective \"early warning\" mechanism that\ndevelopers may leverage to detect deprecated API usage.
When set to 1, instructs the module loader to preserve symbolic links when\nresolving and caching modules.
When set, process warnings will be emitted to the given file instead of\nprinting to stderr. The file will be created if it does not exist, and will be\nappended to if it does. If an error occurs while attempting to write the\nwarning to the file, the warning will be written to stderr instead. This is\nequivalent to using the --redirect-warnings=file command-line flag.
Path to the file used to store the persistent REPL history. The default path is\n~/.node_repl_history, which is overridden by this variable. Setting the value\nto an empty string ('' or ' ') disables persistent REPL history.
If value equals '0', certificate validation is disabled for TLS connections.\nThis makes TLS, and HTTPS by extension, insecure. The use of this environment\nvariable is strongly discouraged.
When set, Node.js will begin outputting V8 JavaScript code coverage to the\ndirectory provided as an argument. Coverage is output as an array of\nScriptCoverage objects:
\n{\n \"result\": [\n {\n \"scriptId\": \"67\",\n \"url\": \"internal/tty.js\",\n \"functions\": []\n }\n ]\n}\nNODE_V8_COVERAGE will automatically propagate to subprocesses, making it\neasier to instrument applications that call the child_process.spawn() family\nof functions. NODE_V8_COVERAGE can be set to an empty string, to prevent\npropagation.
At this time coverage is only collected in the main thread and will not be\noutput for code executed by worker threads.
", "type": "module", "displayName": "`NODE_V8_COVERAGE=dir`" }, { "textRaw": "`OPENSSL_CONF=file`", "name": "`openssl_conf=file`", "meta": { "added": [ "v6.11.0" ], "changes": [] }, "desc": "Load an OpenSSL configuration file on startup. Among other uses, this can be\nused to enable FIPS-compliant crypto if Node.js is built with ./configure --openssl-fips.
If the --openssl-config command line option is used, the environment\nvariable is ignored.
If --use-openssl-ca is enabled, this overrides and sets OpenSSL's directory\ncontaining trusted certificates.
Be aware that unless the child environment is explicitly set, this environment\nvariable will be inherited by any child processes, and if they use OpenSSL, it\nmay cause them to trust the same CAs as node.
", "type": "module", "displayName": "`SSL_CERT_DIR=dir`" }, { "textRaw": "`SSL_CERT_FILE=file`", "name": "`ssl_cert_file=file`", "meta": { "added": [ "v7.7.0" ], "changes": [] }, "desc": "If --use-openssl-ca is enabled, this overrides and sets OpenSSL's file\ncontaining trusted certificates.
Be aware that unless the child environment is explicitly set, this environment\nvariable will be inherited by any child processes, and if they use OpenSSL, it\nmay cause them to trust the same CAs as node.
", "type": "module", "displayName": "`SSL_CERT_FILE=file`" }, { "textRaw": "`UV_THREADPOOL_SIZE=size`", "name": "`uv_threadpool_size=size`", "desc": "Set the number of threads used in libuv's threadpool to size threads.
Asynchronous system APIs are used by Node.js whenever possible, but where they\ndo not exist, libuv's threadpool is used to create asynchronous node APIs based\non synchronous system APIs. Node.js APIs that use the threadpool are:
\nfs APIs, other than the file watcher APIs and those that are explicitly\nsynchronouscrypto.pbkdf2()crypto.randomBytes(), unless it is used without a callbackcrypto.randomFill()dns.lookup()zlib APIs, other than those that are explicitly synchronousBecause libuv's threadpool has a fixed size, it means that if for whatever\nreason any of these APIs takes a long time, other (seemingly unrelated) APIs\nthat run in libuv's threadpool will experience degraded performance. In order to\nmitigate this issue, one potential solution is to increase the size of libuv's\nthreadpool by setting the 'UV_THREADPOOL_SIZE' environment variable to a value\ngreater than 4 (its current default value). For more information, see the\nlibuv threadpool documentation.
Node.js includes an out-of-process debugging utility accessible via a\nV8 Inspector and built-in debugging client. To use it, start Node.js\nwith the inspect argument followed by the path to the script to debug; a\nprompt will be displayed indicating successful launch of the debugger:
$ node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in myscript.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n 3 console.log('world');\ndebug>\nNode.js's debugger client is not a full-featured debugger, but simple step and\ninspection are possible.
\nInserting the statement debugger; into the source code of a script will\nenable a breakpoint at that position in the code:
// myscript.js\nglobal.x = 5;\nsetTimeout(() => {\n debugger;\n console.log('world');\n}, 1000);\nconsole.log('hello');\nOnce the debugger is run, a breakpoint will occur at line 3:
\n$ node inspect myscript.js\n< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in myscript.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n 3 debugger;\ndebug> cont\n< hello\nbreak in myscript.js:3\n 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;\n 2 setTimeout(() => {\n> 3 debugger;\n 4 console.log('world');\n 5 }, 1000);\ndebug> next\nbreak in myscript.js:4\n 2 setTimeout(() => {\n 3 debugger;\n> 4 console.log('world');\n 5 }, 1000);\n 6 console.log('hello');\ndebug> repl\nPress Ctrl + C to leave debug repl\n> x\n5\n> 2 + 2\n4\ndebug> next\n< world\nbreak in myscript.js:5\n 3 debugger;\n 4 console.log('world');\n> 5 }, 1000);\n 6 console.log('hello');\n 7\ndebug> .exit\nThe repl command allows code to be evaluated remotely. The next command\nsteps to the next line. Type help to see what other commands are available.
Pressing enter without typing a command will repeat the previous debugger\ncommand.
It is possible to watch expression and variable values while debugging. On\nevery breakpoint, each expression from the watchers list will be evaluated\nin the current context and displayed immediately before the breakpoint's\nsource code listing.
\nTo begin watching an expression, type watch('my_expression'). The command\nwatchers will print the active watchers. To remove a watcher, type\nunwatch('my_expression').
cont, c - Continue executionnext, n - Step nextstep, s - Step inout, o - Step outpause - Pause running code (like pause button in Developer Tools)setBreakpoint(), sb() - Set breakpoint on current linesetBreakpoint(line), sb(line) - Set breakpoint on specific linesetBreakpoint('fn()'), sb(...) - Set breakpoint on a first statement in\nfunctions bodysetBreakpoint('script.js', 1), sb(...) - Set breakpoint on first line of\nscript.jsclearBreakpoint('script.js', 1), cb(...) - Clear breakpoint in script.js\non line 1It is also possible to set a breakpoint in a file (module) that\nis not loaded yet:
\n$ node inspect main.js\n< Debugger listening on ws://127.0.0.1:9229/4e3db158-9791-4274-8909-914f7facf3bd\n< For help, see: https://nodejs.org/en/docs/inspector\n< Debugger attached.\nBreak on start in main.js:1\n> 1 (function (exports, require, module, __filename, __dirname) { const mod = require('./mod.js');\n 2 mod.hello();\n 3 mod.hello();\ndebug> setBreakpoint('mod.js', 22)\nWarning: script 'mod.js' was not loaded yet.\ndebug> c\nbreak in mod.js:22\n 20 // USE OR OTHER DEALINGS IN THE SOFTWARE.\n 21\n>22 exports.hello = function() {\n 23 return 'hello from module';\n 24 };\ndebug>\nbacktrace, bt - Print backtrace of current execution framelist(5) - List scripts source code with 5 line context (5 lines before and\nafter)watch(expr) - Add expression to watch listunwatch(expr) - Remove expression from watch listwatchers - List all watchers and their values (automatically listed on each\nbreakpoint)repl - Open debugger's repl for evaluation in debugging script's contextexec expr - Execute an expression in debugging script's contextrun - Run script (automatically runs on debugger's start)restart - Restart scriptkill - Kill scriptscripts - List all loaded scriptsversion - Display V8's versionV8 Inspector integration allows attaching Chrome DevTools to Node.js\ninstances for debugging and profiling. It uses the\nChrome DevTools Protocol.
\nV8 Inspector can be enabled by passing the --inspect flag when starting a\nNode.js application. It is also possible to supply a custom port with that flag,\ne.g. --inspect=9222 will accept DevTools connections on port 9222.
To break on the first line of the application code, pass the --inspect-brk\nflag instead of --inspect.
$ node --inspect index.js\nDebugger listening on 127.0.0.1:9229.\nTo start debugging, open the following URL in Chrome:\n chrome-devtools://devtools/bundled/js_app.html?experiments=true&v8only=true&ws=127.0.0.1:9229/dc9010dd-f8b8-4ac5-a510-c1a114ec7d29\n(In the example above, the UUID dc9010dd-f8b8-4ac5-a510-c1a114ec7d29\nat the end of the URL is generated on the fly, it varies in different\ndebugging sessions.)
\nIf the Chrome browser is older than 66.0.3345.0,\nuse inspector.html instead of js_app.html in the above URL.
Node.js may deprecate APIs when either: (a) use of the API is considered to be\nunsafe, (b) an improved alternative API is available, or (c) breaking changes to\nthe API are expected in a future major release.
\nNode.js utilizes three kinds of Deprecations:
\nA Documentation-only deprecation is one that is expressed only within the\nNode.js API docs. These generate no side-effects while running Node.js.\nSome Documentation-only deprecations trigger a runtime warning when launched\nwith --pending-deprecation flag (or its alternative,\nNODE_PENDING_DEPRECATION=1 environment variable), similarly to Runtime\ndeprecations below. Documentation-only deprecations that support that flag\nare explicitly labeled as such in the\nlist of Deprecated APIs.
A Runtime deprecation will, by default, generate a process warning that will\nbe printed to stderr the first time the deprecated API is used. When the\n--throw-deprecation command-line flag is used, a Runtime deprecation will\ncause an error to be thrown.
An End-of-Life deprecation is used when functionality is or will soon be removed\nfrom Node.js.
", "miscs": [ { "textRaw": "Revoking deprecations", "name": "revoking_deprecations", "desc": "Occasionally, the deprecation of an API may be reversed. In such situations,\nthis document will be updated with information relevant to the decision.\nHowever, the deprecation identifier will not be modified.
", "type": "misc", "displayName": "Revoking deprecations" }, { "textRaw": "List of Deprecated APIs", "name": "list_of_deprecated_apis", "desc": "", "modules": [ { "textRaw": "DEP0001: http.OutgoingMessage.prototype.flush", "name": "dep0001:_http.outgoingmessage.prototype.flush", "meta": { "changes": [ { "version": [ "v4.8.6", "v6.12.0" ], "pr-url": "https://github.com/nodejs/node/pull/10116", "description": "A deprecation code has been assigned." }, { "version": "v1.6.0", "pr-url": "https://github.com/nodejs/node/pull/1156", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nThe OutgoingMessage.prototype.flush() method is deprecated. Use\nOutgoingMessage.prototype.flushHeaders() instead.
Type: End-of-Life
\nThe _linklist module is deprecated. Please use a userland alternative.
Type: Runtime
\nThe _writableState.buffer property is deprecated. Use the\n_writableState.getBuffer() method instead.
Type: End-of-Life
\nThe CryptoStream.prototype.readyState property was removed.
Type: Runtime (supports --pending-deprecation)
The Buffer() function and new Buffer() constructor are deprecated due to\nAPI usability issues that can potentially lead to accidental security issues.
As an alternative, use of the following methods of constructing Buffer objects\nis strongly recommended:
Buffer.alloc(size[, fill[, encoding]]) - Create a Buffer with\ninitialized memory.Buffer.allocUnsafe(size) - Create a Buffer with\nuninitialized memory.Buffer.allocUnsafeSlow(size) - Create a Buffer with uninitialized\nmemory.Buffer.from(array) - Create a Buffer with a copy of arrayBuffer.from(arrayBuffer[, byteOffset[, length]]) -\nCreate a Buffer that wraps the given arrayBuffer.Buffer.from(buffer) - Create a Buffer that copies buffer.Buffer.from(string[, encoding]) - Create a Buffer\nthat copies string.As of v10.0.0, a deprecation warning is printed at runtime when\n--pending-deprecation is used or when the calling code is\noutside node_modules in order to better target developers, rather than users.
Type: Runtime
\nWithin the child_process module's spawn(), fork(), and exec()\nmethods, the options.customFds option is deprecated. The options.stdio\noption should be used instead.
Type: End-of-Life
\nIn an earlier version of the Node.js cluster, a boolean property with the name\nsuicide was added to the Worker object. The intent of this property was to\nprovide an indication of how and why the Worker instance exited. In Node.js\n6.0.0, the old property was deprecated and replaced with a new\nworker.exitedAfterDisconnect property. The old property name did not\nprecisely describe the actual semantics and was unnecessarily emotion-laden.
Type: Documentation-only
\nThe constants module is deprecated. When requiring access to constants\nrelevant to specific Node.js builtin modules, developers should instead refer\nto the constants property exposed by the relevant module. For instance,\nrequire('fs').constants and require('os').constants.
Type: End-of-Life
\nUse of the crypto.pbkdf2() API without specifying a digest was deprecated\nin Node.js 6.0 because the method defaulted to using the non-recommended\n'SHA1' digest. Previously, a deprecation warning was printed. Starting in\nNode.js 8.0.0, calling crypto.pbkdf2() or crypto.pbkdf2Sync() with an\nundefined digest will throw a TypeError.
Type: Runtime
\nThe crypto.createCredentials() API is deprecated. Please use\ntls.createSecureContext() instead.
Type: Runtime
\nThe crypto.Credentials class is deprecated. Please use tls.SecureContext\ninstead.
Type: End-of-Life
\nDomain.dispose() has been removed. Recover from failed I/O actions\nexplicitly via error event handlers set on the domain instead.
Type: End-of-Life
\nCalling an asynchronous function without a callback throws a TypeError\nin Node.js 10.0.0 onwards. (See https://github.com/nodejs/node/pull/12562.)
Type: End-of-Life
\nThe fs.read() legacy String interface is deprecated. Use the Buffer\nAPI as mentioned in the documentation instead.
Type: End-of-Life
\nThe fs.readSync() legacy String interface is deprecated. Use the\nBuffer API as mentioned in the documentation instead.
Type: Runtime
\nThe GLOBAL and root aliases for the global property are deprecated\nand should no longer be used.
Type: End-of-Life
\nIntl.v8BreakIterator was a non-standard extension and has been removed.\nSee Intl.Segmenter.
Type: Runtime
\nUnhandled promise rejections are deprecated. In the future, promise rejections\nthat are not handled will terminate the Node.js process with a non-zero exit\ncode.
\n", "type": "module", "displayName": "DEP0018: Unhandled promise rejections" }, { "textRaw": "DEP0019: require('.') resolved outside directory", "name": "dep0019:_require('.')_resolved_outside_directory", "meta": { "changes": [ { "version": [ "v4.8.6", "v6.12.0" ], "pr-url": "https://github.com/nodejs/node/pull/10116", "description": "A deprecation code has been assigned." }, { "version": "v1.8.1", "pr-url": "https://github.com/nodejs/node/pull/1363", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nIn certain cases, require('.') may resolve outside the package directory.\nThis behavior is deprecated and will be removed in a future major Node.js\nrelease.
Type: Runtime
\nThe Server.connections property is deprecated. Please use the\nServer.getConnections() method instead.
Type: Runtime
\nThe Server.listenFD() method is deprecated. Please use\nServer.listen({fd: <number>}) instead.
Type: Runtime
\nThe os.tmpDir() API is deprecated. Please use os.tmpdir() instead.
Type: Runtime
\nThe os.getNetworkInterfaces() method is deprecated. Please use the\nos.networkInterfaces property instead.
Type: End-of-Life
\nThe REPLServer.prototype.convertToContext() API has been removed.
Type: Runtime
\nThe sys module is deprecated. Please use the util module instead.
Type: Runtime
\nThe util.print() API is deprecated. Please use console.log()\ninstead.
Type: Runtime
\nThe util.puts() API is deprecated. Please use console.log() instead.
Type: Runtime
\nThe util.debug() API is deprecated. Please use console.error()\ninstead.
Type: Runtime
\nThe util.error() API is deprecated. Please use console.error()\ninstead.
Type: Documentation-only
\nThe SlowBuffer class is deprecated. Please use\nBuffer.allocUnsafeSlow(size) instead.
Type: Documentation-only
\nThe ecdh.setPublicKey() method is now deprecated as its inclusion in the\nAPI is not useful.
Type: Documentation-only
\nThe domain module is deprecated and should not be used.
Type: Documentation-only
\nThe EventEmitter.listenerCount(emitter, eventName) API is\ndeprecated. Please use emitter.listenerCount(eventName) instead.
Type: Documentation-only
\nThe fs.exists(path, callback) API is deprecated. Please use\nfs.stat() or fs.access() instead.
Type: Documentation-only
\nThe fs.lchmod(path, mode, callback) API is deprecated.
Type: Documentation-only
\nThe fs.lchmodSync(path, mode) API is deprecated.
Type: Deprecation revoked
\nThe fs.lchown(path, uid, gid, callback) API is deprecated.
Type: Deprecation revoked
\nThe fs.lchownSync(path, uid, gid) API is deprecated.
Type: Documentation-only
\nThe require.extensions property is deprecated.
Type: Documentation-only
\nThe punycode module is deprecated. Please use a userland alternative\ninstead.
Type: End-of-Life
\nThe NODE_REPL_HISTORY_FILE environment variable was removed. Please use\nNODE_REPL_HISTORY instead.
Type: End-of-Life
\nThe tls.CryptoStream class was removed. Please use\ntls.TLSSocket instead.
Type: Documentation-only
\nThe tls.SecurePair class is deprecated. Please use\ntls.TLSSocket instead.
Type: Documentation-only
\nThe util.isArray() API is deprecated. Please use Array.isArray()\ninstead.
Type: Documentation-only
\nThe util.isBoolean() API is deprecated.
Type: Documentation-only
\nThe util.isBuffer() API is deprecated. Please use\nBuffer.isBuffer() instead.
Type: Documentation-only
\nThe util.isDate() API is deprecated.
Type: Documentation-only
\nThe util.isError() API is deprecated.
Type: Documentation-only
\nThe util.isFunction() API is deprecated.
Type: Documentation-only
\nThe util.isNull() API is deprecated.
Type: Documentation-only
\nThe util.isNullOrUndefined() API is deprecated.
Type: Documentation-only
\nThe util.isNumber() API is deprecated.
Type: Documentation-only
\nThe util.isObject() API is deprecated.
Type: Documentation-only
\nThe util.isPrimitive() API is deprecated.
Type: Documentation-only
\nThe util.isRegExp() API is deprecated.
Type: Documentation-only
\nThe util.isString() API is deprecated.
Type: Documentation-only
\nThe util.isSymbol() API is deprecated.
Type: Documentation-only
\nThe util.isUndefined() API is deprecated.
Type: Documentation-only
\nThe util.log() API is deprecated.
Type: Documentation-only
\nThe util._extend() API is deprecated.
Type: Runtime
\nThe fs.SyncWriteStream class was never intended to be a publicly accessible\nAPI. No alternative API is available. Please use a userland alternative.
Type: Runtime
\n--debug activates the legacy V8 debugger interface, which was removed as\nof V8 5.8. It is replaced by Inspector which is activated with --inspect\ninstead.
Type: Documentation-only
\nThe http module ServerResponse.prototype.writeHeader() API is\ndeprecated. Please use ServerResponse.prototype.writeHead() instead.
The ServerResponse.prototype.writeHeader() method was never documented as an\nofficially supported API.
Type: Runtime
\nThe tls.createSecurePair() API was deprecated in documentation in Node.js\n0.11.3. Users should use tls.Socket instead.
Type: End-of-Life
\nThe repl module's REPL_MODE_MAGIC constant, used for replMode option, has\nbeen removed. Its behavior has been functionally identical to that of\nREPL_MODE_SLOPPY since Node.js 6.0.0, when V8 5.0 was imported. Please use\nREPL_MODE_SLOPPY instead.
The NODE_REPL_MODE environment variable is used to set the underlying\nreplMode of an interactive node session. Its value, magic, is also\nremoved. Please use sloppy instead.
Type: Documentation-only
\nThe http module outgoingMessage._headers and outgoingMessage._headerNames\nproperties are deprecated. Use one of the public methods\n(e.g. outgoingMessage.getHeader(), outgoingMessage.getHeaders(),\noutgoingMessage.getHeaderNames(), outgoingMessage.hasHeader(),\noutgoingMessage.removeHeader(), outgoingMessage.setHeader()) for working\nwith outgoing headers.
The outgoingMessage._headers and outgoingMessage._headerNames properties\nwere never documented as officially supported properties.
Type: Documentation-only
\nThe http module OutgoingMessage.prototype._renderHeaders() API is\ndeprecated.
The OutgoingMessage.prototype._renderHeaders property was never documented as\nan officially supported API.
Type: Runtime
\nnode debug corresponds to the legacy CLI debugger which has been replaced with\na V8-inspector based CLI debugger available through node inspect.
Type: End-of-Life
\nDebugContext has been removed in V8 and is not available in Node.js 10+.
\nDebugContext was an experimental API.
\n", "type": "module", "displayName": "DEP0069: vm.runInDebugContext(string)" }, { "textRaw": "DEP0070: async_hooks.currentId()", "name": "dep0070:_async_hooks.currentid()", "meta": { "changes": [ { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/14414", "description": "End-of-Life." }, { "version": "v8.2.0", "pr-url": "https://github.com/nodejs/node/pull/13490", "description": "Runtime deprecation." } ] }, "desc": "Type: End-of-Life
\nasync_hooks.currentId() was renamed to async_hooks.executionAsyncId() for\nclarity.
This change was made while async_hooks was an experimental API.
Type: End-of-Life
\nasync_hooks.triggerId() was renamed to async_hooks.triggerAsyncId() for\nclarity.
This change was made while async_hooks was an experimental API.
Type: End-of-Life
\nasync_hooks.AsyncResource.triggerId() was renamed to\nasync_hooks.AsyncResource.triggerAsyncId() for clarity.
This change was made while async_hooks was an experimental API.
Type: End-of-Life
\nAccessing several internal, undocumented properties of net.Server instances\nwith inappropriate names is deprecated.
As the original API was undocumented and not generally useful for non-internal\ncode, no replacement API is provided.
\n", "type": "module", "displayName": "DEP0073: Several internal properties of net.Server" }, { "textRaw": "DEP0074: REPLServer.bufferedCommand", "name": "dep0074:_replserver.bufferedcommand", "meta": { "changes": [ { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/13687", "description": "Runtime deprecation." } ] }, "desc": "Type: Runtime
\nThe REPLServer.bufferedCommand property was deprecated in favor of\nREPLServer.clearBufferedCommand().
Type: Runtime
\nREPLServer.parseREPLKeyword() was removed from userland visibility.
Type: Runtime
\ntls.parseCertString() is a trivial parsing helper that was made public by\nmistake. This function can usually be replaced with:
const querystring = require('querystring');\nquerystring.parse(str, '\\n', '=');\nThis function is not completely equivalent to querystring.parse(). One\ndifference is that querystring.parse() does url decoding:
> querystring.parse('%E5%A5%BD=1', '\\n', '=');\n{ '好': '1' }\n> tls.parseCertString('%E5%A5%BD=1');\n{ '%E5%A5%BD': '1' }\nType: Runtime
\nModule._debug() is deprecated.
The Module._debug() function was never documented as an officially\nsupported API.
Type: Runtime
\nREPLServer.turnOffEditorMode() was removed from userland visibility.
Type: Runtime
\nUsing a property named inspect on an object to specify a custom inspection\nfunction for util.inspect() is deprecated. Use util.inspect.custom\ninstead. For backward compatibility with Node.js prior to version 6.4.0, both\nmay be specified.
Type: Documentation-only
\nThe internal path._makeLong() was not intended for public use. However,\nuserland modules have found it useful. The internal API is deprecated\nand replaced with an identical, public path.toNamespacedPath() method.
Type: Runtime
\nfs.truncate() fs.truncateSync() usage with a file descriptor is\ndeprecated. Please use fs.ftruncate() or fs.ftruncateSync() to work with\nfile descriptors.
Type: Runtime
\nREPLServer.prototype.memory() is only necessary for the internal mechanics of\nthe REPLServer itself. Do not use this function.
Type: End-of-Life.
\nThe ecdhCurve option to tls.createSecureContext() and tls.TLSSocket could\nbe set to false to disable ECDH entirely on the server only. This mode was\ndeprecated in preparation for migrating to OpenSSL 1.1.0 and consistency with\nthe client and is now unsupported. Use the ciphers parameter instead.
Type: Runtime
\nSince Node.js versions 4.4.0 and 5.2.0, several modules only intended for\ninternal usage are mistakenly exposed to user code through require(). These\nmodules are:
v8/tools/codemapv8/tools/consarrayv8/tools/csvparserv8/tools/logreaderv8/tools/profile_viewv8/tools/profilev8/tools/SourceMapv8/tools/splaytreev8/tools/tickprocessor-driverv8/tools/tickprocessornode-inspect/lib/_inspect (from 7.6.0)node-inspect/lib/internal/inspect_client (from 7.6.0)node-inspect/lib/internal/inspect_repl (from 7.6.0)The v8/* modules do not have any exports, and if not imported in a specific\norder would in fact throw errors. As such there are virtually no legitimate use\ncases for importing them through require().
On the other hand, node-inspect may be installed locally through a package\nmanager, as it is published on the npm registry under the same name. No source\ncode modification is necessary if that is done.
Type: End-of-Life
\nThe AsyncHooks Sensitive API was never documented and had various minor issues.\n(See https://github.com/nodejs/node/issues/15572.) Use the AsyncResource\nAPI instead.
Type: End-of-Life
\nrunInAsyncIdScope doesn't emit the 'before' or 'after' event and can thus\ncause a lot of issues. See https://github.com/nodejs/node/issues/14328 for\nmore details.
Type: Documentation-only
\nImporting assert directly is not recommended as the exposed functions will use\nloose equality checks. Use require('assert').strict instead. The API is the\nsame as the legacy assert but it will always use strict equality checks.
Type: Runtime
\nNode.js supports all GCM authentication tag lengths which are accepted by\nOpenSSL when calling decipher.setAuthTag(). This behavior will change in\na future version at which point only authentication tag lengths of 128, 120,\n112, 104, 96, 64, and 32 bits will be allowed. Authentication tags whose length\nis not included in this list will be considered invalid in compliance with\nNIST SP 800-38D.
Type: Runtime
\nThe crypto.DEFAULT_ENCODING property is deprecated.
Type: Documentation-only
\nAssigning properties to the top-level this as an alternative\nto module.exports is deprecated. Developers should use exports\nor module.exports instead.
Type: Documentation-only
\nThe crypto.fips property is deprecated. Please use crypto.setFips()\nand crypto.getFips() instead.
Type: Runtime
\nUsing assert.fail() with more than one argument is deprecated. Use\nassert.fail() with only one argument or use a different assert module\nmethod.
Type: Runtime
\ntimers.enroll() is deprecated. Please use the publicly documented\nsetTimeout() or setInterval() instead.
Type: Runtime
\ntimers.unenroll() is deprecated. Please use the publicly documented\nclearTimeout() or clearInterval() instead.
Type: Runtime
\nUsers of MakeCallback that add the domain property to carry context,\nshould start using the async_context variant of MakeCallback or\nCallbackScope, or the high-level AsyncResource class.
Type: Runtime
\nThe embedded API provided by AsyncHooks exposes .emitBefore() and\n.emitAfter() methods which are very easy to use incorrectly which can lead\nto unrecoverable errors.
Use asyncResource.runInAsyncScope() API instead which provides a much\nsafer, and more convenient, alternative. See\nhttps://github.com/nodejs/node/pull/18513 for more details.
Type: Compile-time
\nCertain versions of node::MakeCallback APIs available to native modules are\ndeprecated. Please use the versions of the API that accept an async_context\nparameter.
Type: Runtime
\nprocess.assert() is deprecated. Please use the assert module instead.
This was never a documented feature.
\n", "type": "module", "displayName": "DEP0100: process.assert()" }, { "textRaw": "DEP0101: --with-lttng", "name": "dep0101:_--with-lttng", "meta": { "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/18982", "description": "End-of-Life." } ] }, "desc": "Type: End-of-Life
\nThe --with-lttng compile-time option has been removed.
Type: End-of-Life
\nUsing the noAssert argument has no functionality anymore. All input is going\nto be verified, no matter if it is set to true or not. Skipping the verification\ncould lead to hard to find errors and crashes.
Type: Documentation-only (supports --pending-deprecation)
Using process.binding() in general should be avoided. The type checking\nmethods in particular can be replaced by using util.types.
This deprecation has been superseded by the deprecation of the\nprocess.binding() API (DEP0111).
Type: Documentation-only (supports --pending-deprecation)
When assigning a non-string property to process.env, the assigned value is\nimplicitly converted to a string. This behavior is deprecated if the assigned\nvalue is not a string, boolean, or number. In the future, such assignment may\nresult in a thrown error. Please convert the property to a string before\nassigning it to process.env.
Type: Runtime
\ndecipher.finaltol() has never been documented and is currently an alias for\ndecipher.final(). In the future, this API will likely be removed, and it\nis recommended to use decipher.final() instead.
Type: Documentation-only
\nUsing crypto.createCipher() and crypto.createDecipher() should be\navoided as they use a weak key derivation function (MD5 with no salt) and static\ninitialization vectors. It is recommended to derive a key using\ncrypto.pbkdf2() or crypto.scrypt() and to use\ncrypto.createCipheriv() and crypto.createDecipheriv() to obtain the\nCipher and Decipher objects respectively.
Type: Runtime
\nThis was an undocumented helper function not intended for use outside Node.js\ncore and obsoleted by the removal of NPN (Next Protocol Negotiation) support.
\n", "type": "module", "displayName": "DEP0107: tls.convertNPNProtocols()" }, { "textRaw": "DEP0108: zlib.bytesRead", "name": "dep0108:_zlib.bytesread", "meta": { "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19414", "description": "Documentation-only deprecation." } ] }, "desc": "Type: Documentation-only
\nDeprecated alias for zlib.bytesWritten. This original name was chosen\nbecause it also made sense to interpret the value as the number of bytes\nread by the engine, but is inconsistent with other streams in Node.js that\nexpose values under these names.
Type: Documentation-only
\nThe produceCachedData option is deprecated. Use\nscript.createCachedData() instead.
Type: Documentation-only
\nprocess.binding() is for use by Node.js internal code only.
Node.js contains support for ES Modules based upon the\nNode.js EP for ES Modules.
\nNot all features of the EP are complete and will be landing as both VM support\nand implementation is ready. Error messages are still being polished.
", "miscs": [ { "textRaw": "Enabling", "name": "Enabling", "type": "misc", "desc": "The --experimental-modules flag can be used to enable features for loading\nESM modules.
Once this has been set, files ending with .mjs will be able to be loaded\nas ES Modules.
node --experimental-modules my-app.mjs\nOnly the CLI argument for the main entry point to the program can be an entry\npoint into an ESM graph. Dynamic import can also be used to create entry points\ninto ESM graphs at runtime.
", "properties": [ { "textRaw": "`meta` {Object}", "type": "Object", "name": "meta", "desc": "The import.meta metaproperty is an Object that contains the following\nproperty:
url <string> The absolute file: URL of the module.| Feature | \nReason | \n
|---|---|
require('./foo.mjs') | \nES Modules have differing resolution and timing, use dynamic import | \n
NODE_PATH is not part of resolving import specifiers. Please use symlinks\nif this behavior is desired.
require.extensions is not used by import. The expectation is that loader\nhooks can provide this workflow in the future.
require.cache is not used by import. It has a separate cache.
ESM are resolved and cached based upon URL\nsemantics. This means that files containing special characters such as # and\n? need to be escaped.
Modules will be loaded multiple times if the import specifier used to resolve\nthem have a different query or fragment.
import './foo?query=1'; // loads ./foo with query of \"?query=1\"\nimport './foo?query=2'; // loads ./foo with query of \"?query=2\"\nFor now, only modules using the file: protocol can be loaded.
All CommonJS, JSON, and C++ modules can be used with import.
Modules loaded this way will only be loaded once, even if their query\nor fragment string differs between import statements.
When loaded via import these modules will provide a single default export\nrepresenting the value of module.exports at the time they finished evaluating.
// foo.js\nmodule.exports = { one: 1 };\n\n// bar.mjs\nimport foo from './foo.js';\nfoo.one === 1; // true\nBuiltin modules will provide named exports of their public API, as well as a\ndefault export which can be used for, among other things, modifying the named\nexports. Named exports of builtin modules are updated when the corresponding\nexports property is accessed, redefined, or deleted.
\nimport EventEmitter from 'events';\nconst e = new EventEmitter();\nimport { readFile } from 'fs';\nreadFile('./foo.txt', (err, source) => {\n if (err) {\n console.error(err);\n } else {\n console.log(source);\n }\n});\nimport fs, { readFileSync } from 'fs';\n\nfs.readFileSync = () => Buffer.from('Hello, ESM');\n\nfs.readFileSync === readFileSync;\nTo customize the default module resolution, loader hooks can optionally be\nprovided via a --loader ./loader-name.mjs argument to Node.js.
When hooks are used they only apply to ES module loading and not to any\nCommonJS modules loaded.
", "miscs": [ { "textRaw": "Resolve hook", "name": "resolve_hook", "desc": "The resolve hook returns the resolved file URL and module format for a\ngiven module specifier and parent file URL:
\nconst baseURL = new URL('file://');\nbaseURL.pathname = `${process.cwd()}/`;\n\nexport async function resolve(specifier,\n parentModuleURL = baseURL,\n defaultResolver) {\n return {\n url: new URL(specifier, parentModuleURL).href,\n format: 'esm'\n };\n}\nThe parentModuleURL is provided as undefined when performing main Node.js\nload itself.
The default Node.js ES module resolution function is provided as a third\nargument to the resolver for easy compatibility workflows.
\nIn addition to returning the resolved file URL value, the resolve hook also\nreturns a format property specifying the module format of the resolved\nmodule. This can be one of the following:
format | \nDescription | \n
|---|---|
'esm' | \nLoad a standard JavaScript module | \n
'cjs' | \nLoad a node-style CommonJS module | \n
'builtin' | \nLoad a node builtin CommonJS module | \n
'json' | \nLoad a JSON file | \n
'addon' | \nLoad a C++ Addon | \n
'dynamic' | \nUse a dynamic instantiate hook | \n
For example, a dummy loader to load JavaScript restricted to browser resolution\nrules with only JS file extension and Node.js builtin modules support could\nbe written:
\nimport path from 'path';\nimport process from 'process';\nimport Module from 'module';\n\nconst builtins = Module.builtinModules;\nconst JS_EXTENSIONS = new Set(['.js', '.mjs']);\n\nconst baseURL = new URL('file://');\nbaseURL.pathname = `${process.cwd()}/`;\n\nexport function resolve(specifier, parentModuleURL = baseURL, defaultResolve) {\n if (builtins.includes(specifier)) {\n return {\n url: specifier,\n format: 'builtin'\n };\n }\n if (/^\\.{0,2}[/]/.test(specifier) !== true && !specifier.startsWith('file:')) {\n // For node_modules support:\n // return defaultResolve(specifier, parentModuleURL);\n throw new Error(\n `imports must begin with '/', './', or '../'; '${specifier}' does not`);\n }\n const resolved = new URL(specifier, parentModuleURL);\n const ext = path.extname(resolved.pathname);\n if (!JS_EXTENSIONS.has(ext)) {\n throw new Error(\n `Cannot load file with non-JavaScript file extension ${ext}.`);\n }\n return {\n url: resolved.href,\n format: 'esm'\n };\n}\nWith this loader, running:
\nNODE_OPTIONS='--experimental-modules --loader ./custom-loader.mjs' node x.js\nwould load the module x.js as an ES module with relative resolution support\n(with node_modules loading skipped in this example).
To create a custom dynamic module that doesn't correspond to one of the\nexisting format interpretations, the dynamicInstantiate hook can be used.\nThis hook is called only for modules that return format: 'dynamic' from\nthe resolve hook.
export async function dynamicInstantiate(url) {\n return {\n exports: ['customExportName'],\n execute: (exports) => {\n // get and set functions provided for pre-allocated export names\n exports.customExportName.set('value');\n }\n };\n}\nWith the list of module exports provided upfront, the execute function will\nthen be called at the exact point of module evaluation order for that module\nin the import tree.
Applications running in Node.js will generally experience four categories of\nerrors:
\nAssertionErrors are a special class of error that can be triggered when\nNode.js detects an exceptional logic violation that should never occur. These\nare raised typically by the assert module.All JavaScript and System errors raised by Node.js inherit from, or are\ninstances of, the standard JavaScript <Error> class and are guaranteed\nto provide at least the properties available on that class.
", "miscs": [ { "textRaw": "Error Propagation and Interception", "name": "Error Propagation and Interception", "type": "misc", "desc": "Node.js supports several mechanisms for propagating and handling errors that\noccur while an application is running. How these errors are reported and\nhandled depends entirely on the type of Error and the style of the API that is\ncalled.
All JavaScript errors are handled as exceptions that immediately generate\nand throw an error using the standard JavaScript throw mechanism. These\nare handled using the try…catch construct provided by the\nJavaScript language.
// Throws with a ReferenceError because z is not defined.\ntry {\n const m = 1;\n const n = m + z;\n} catch (err) {\n // Handle the error here.\n}\nAny use of the JavaScript throw mechanism will raise an exception that\nmust be handled using try…catch or the Node.js process will exit\nimmediately.
With few exceptions, Synchronous APIs (any blocking method that does not\naccept a callback function, such as fs.readFileSync), will use throw\nto report errors.
Errors that occur within Asynchronous APIs may be reported in multiple ways:
\ncallback function will accept an\nError object passed as the first argument to that function. If that first\nargument is not null and is an instance of Error, then an error occurred\nthat should be handled.const fs = require('fs');\nfs.readFile('a file that does not exist', (err, data) => {\n if (err) {\n console.error('There was an error reading the file!', err);\n return;\n }\n // Otherwise handle the data\n});\nWhen an asynchronous method is called on an object that is an\nEventEmitter, errors can be routed to that object's 'error' event.
const net = require('net');\nconst connection = net.connect('localhost');\n\n// Adding an 'error' event handler to a stream:\nconnection.on('error', (err) => {\n // If the connection is reset by the server, or if it can't\n // connect at all, or on any sort of error encountered by\n // the connection, the error will be sent here.\n console.error(err);\n});\n\nconnection.pipe(process.stdout);\nA handful of typically asynchronous methods in the Node.js API may still\nuse the throw mechanism to raise exceptions that must be handled using\ntry…catch. There is no comprehensive list of such methods; please\nrefer to the documentation of each method to determine the appropriate\nerror handling mechanism required.
The use of the 'error' event mechanism is most common for stream-based\nand event emitter-based APIs, which themselves represent a series of\nasynchronous operations over time (as opposed to a single operation that may\npass or fail).
For all EventEmitter objects, if an 'error' event handler is not\nprovided, the error will be thrown, causing the Node.js process to report an\nuncaught exception and crash unless either: The domain module is\nused appropriately or a handler has been registered for the\n'uncaughtException' event.
const EventEmitter = require('events');\nconst ee = new EventEmitter();\n\nsetImmediate(() => {\n // This will crash the process because no 'error' event\n // handler has been added.\n ee.emit('error', new Error('This will crash'));\n});\nErrors generated in this way cannot be intercepted using try…catch as\nthey are thrown after the calling code has already exited.
Developers must refer to the documentation for each method to determine\nexactly how errors raised by those methods are propagated.
", "miscs": [ { "textRaw": "Error-first callbacks", "name": "Error-first callbacks", "type": "misc", "desc": "Most asynchronous methods exposed by the Node.js core API follow an idiomatic\npattern referred to as an error-first callback. With this pattern, a callback\nfunction is passed to the method as an argument. When the operation either\ncompletes or an error is raised, the callback function is called with the\nError object (if any) passed as the first argument. If no error was raised,\nthe first argument will be passed as null.
const fs = require('fs');\n\nfunction errorFirstCallback(err, data) {\n if (err) {\n console.error('There was an error', err);\n return;\n }\n console.log(data);\n}\n\nfs.readFile('/some/file/that/does-not-exist', errorFirstCallback);\nfs.readFile('/some/file/that/does-exist', errorFirstCallback);\nThe JavaScript try…catch mechanism cannot be used to intercept errors\ngenerated by asynchronous APIs. A common mistake for beginners is to try to\nuse throw inside an error-first callback:
// THIS WILL NOT WORK:\nconst fs = require('fs');\n\ntry {\n fs.readFile('/some/file/that/does-not-exist', (err, data) => {\n // mistaken assumption: throwing here...\n if (err) {\n throw err;\n }\n });\n} catch (err) {\n // This will not catch the throw!\n console.error(err);\n}\nThis will not work because the callback function passed to fs.readFile() is\ncalled asynchronously. By the time the callback has been called, the\nsurrounding code (including the try { } catch (err) { } block will have\nalready exited. Throwing an error inside the callback can crash the Node.js\nprocess in most cases. If domains are enabled, or a handler has been\nregistered with process.on('uncaughtException'), such errors can be\nintercepted.
A JavaScript exception is a value that is thrown as a result of an invalid\noperation or as the target of a throw statement. While it is not required\nthat these values are instances of Error or classes which inherit from\nError, all exceptions thrown by Node.js or the JavaScript runtime will be\ninstances of Error.
Some exceptions are unrecoverable at the JavaScript layer. Such exceptions\nwill always cause the Node.js process to crash. Examples include assert()\nchecks or abort() calls in the C++ layer.
Node.js generates system errors when exceptions occur within its runtime\nenvironment. These usually occur when an application violates an operating\nsystem constraint. For example, a system error will occur if an application\nattempts to read a file that does not exist.
\nSystem errors are usually generated at the syscall level. For a comprehensive\nlist, see the errno(3) man page.
In Node.js, system errors are Error objects with extra properties.
address <string> If present, the address to which a network connection\nfailedcode <string> The string error codedest <string> If present, the file path destination when reporting a file\nsystem errorerrno <number> | <string> The system-provided error numberinfo <Object> If present, extra details about the error conditionmessage <string> A system-provided human-readable description of the errorpath <string> If present, the file path when reporting a file system errorport <number> If present, the network connection port that is not availablesyscall <string> The name of the system call that triggered the errorIf present, error.address is a string describing the address to which a\nnetwork connection failed.
The error.code property is a string representing the error code.
If present, error.dest is the file path destination when reporting a file\nsystem error.
The error.errno property is a number or a string. If it is a number, it is a\nnegative value which corresponds to the error code defined in\nlibuv Error handling. See the libuv errno.h header file\n(deps/uv/include/uv/errno.h in the Node.js source tree) for details. In case\nof a string, it is the same as error.code.
If present, error.info is an object with details about the error condition.
error.message is a system-provided human-readable description of the error.
If present, error.path is a string containing a relevant invalid pathname.
If present, error.port is the network connection port that is not available.
The error.syscall property is a string describing the syscall that failed.
This is a list of system errors commonly-encountered when writing a Node.js\nprogram. For a comprehensive list, see the errno(3) man page.
EACCES (Permission denied): An attempt was made to access a file in a way\nforbidden by its file access permissions.
EADDRINUSE (Address already in use): An attempt to bind a server\n(net, http, or https) to a local address failed due to\nanother server on the local system already occupying that address.
ECONNREFUSED (Connection refused): No connection could be made because the\ntarget machine actively refused it. This usually results from trying to\nconnect to a service that is inactive on the foreign host.
ECONNRESET (Connection reset by peer): A connection was forcibly closed by\na peer. This normally results from a loss of the connection on the remote\nsocket due to a timeout or reboot. Commonly encountered via the http\nand net modules.
EEXIST (File exists): An existing file was the target of an operation that\nrequired that the target not exist.
EISDIR (Is a directory): An operation expected a file, but the given\npathname was a directory.
EMFILE (Too many open files in system): Maximum number of\nfile descriptors allowable on the system has been reached, and\nrequests for another descriptor cannot be fulfilled until at least one\nhas been closed. This is encountered when opening many files at once in\nparallel, especially on systems (in particular, macOS) where there is a low\nfile descriptor limit for processes. To remedy a low limit, run\nulimit -n 2048 in the same shell that will run the Node.js process.
ENOENT (No such file or directory): Commonly raised by fs operations\nto indicate that a component of the specified pathname does not exist — no\nentity (file or directory) could be found by the given path.
ENOTDIR (Not a directory): A component of the given pathname existed, but\nwas not a directory as expected. Commonly raised by fs.readdir.
ENOTEMPTY (Directory not empty): A directory with entries was the target\nof an operation that requires an empty directory — usually fs.unlink.
EPERM (Operation not permitted): An attempt was made to perform an\noperation that requires elevated privileges.
EPIPE (Broken pipe): A write on a pipe, socket, or FIFO for which there is\nno process to read the data. Commonly encountered at the net and\nhttp layers, indicative that the remote side of the stream being\nwritten to has been closed.
ETIMEDOUT (Operation timed out): A connect or send request failed because\nthe connected party did not properly respond after a period of time. Usually\nencountered by http or net — often a sign that a socket.end()\nwas not properly called.
A function argument is being used in a way that suggests that the function\nsignature may be misunderstood. This is thrown by the assert module when the\nmessage parameter in assert.throws(block, message) matches the error message\nthrown by block because that usage suggests that the user believes message\nis the expected message rather than the message the AssertionError will\ndisplay if block does not throw.
An iterable argument (i.e. a value that works with for...of loops) was\nrequired, but not provided to a Node.js API.
A special type of error that can be triggered whenever Node.js detects an\nexceptional logic violation that should never occur. These are raised typically\nby the assert module.
An attempt was made to register something that is not a function as an\nAsyncHooks callback.
The type of an asynchronous resource was invalid. Note that users are also able\nto define their own types if using the public embedder API.
\n", "type": "module", "displayName": "ERR_ASYNC_TYPE" }, { "textRaw": "ERR_BROTLI_COMPRESSION_FAILED", "name": "err_brotli_compression_failed", "desc": "Data passed to a Brotli stream was not successfully compressed.
\n", "type": "module", "displayName": "ERR_BROTLI_COMPRESSION_FAILED" }, { "textRaw": "ERR_BROTLI_INVALID_PARAM", "name": "err_brotli_invalid_param", "desc": "An invalid parameter key was passed during construction of a Brotli stream.
\n", "type": "module", "displayName": "ERR_BROTLI_INVALID_PARAM" }, { "textRaw": "ERR_BUFFER_OUT_OF_BOUNDS", "name": "err_buffer_out_of_bounds", "desc": "An operation outside the bounds of a Buffer was attempted.
An attempt has been made to create a Buffer larger than the maximum allowed\nsize.
The value passed to postMessage() contained an object that is not supported\nfor transferring.
Node.js was unable to watch for the SIGINT signal.
A child process was closed before the parent received a reply.
\n", "type": "module", "displayName": "ERR_CHILD_CLOSED_BEFORE_REPLY" }, { "textRaw": "ERR_CHILD_PROCESS_IPC_REQUIRED", "name": "err_child_process_ipc_required", "desc": "Used when a child process is being forked without specifying an IPC channel.
\n", "type": "module", "displayName": "ERR_CHILD_PROCESS_IPC_REQUIRED" }, { "textRaw": "ERR_CHILD_PROCESS_STDIO_MAXBUFFER", "name": "err_child_process_stdio_maxbuffer", "desc": "Used when the main process is trying to read data from the child process's\nSTDERR/STDOUT, and the data's length is longer than the maxBuffer option.
There was an attempt to use a MessagePort instance in a closed\nstate, usually after .close() has been called.
Console was instantiated without stdout stream, or Console has a\nnon-writable stdout or stderr stream.
A constructor for a class was called without new.
The native call from process.cpuUsage could not be processed.
A client certificate engine was requested that is not supported by the version\nof OpenSSL being used.
\n", "type": "module", "displayName": "ERR_CRYPTO_CUSTOM_ENGINE_NOT_SUPPORTED" }, { "textRaw": "ERR_CRYPTO_ECDH_INVALID_FORMAT", "name": "err_crypto_ecdh_invalid_format", "desc": "An invalid value for the format argument was passed to the crypto.ECDH()\nclass getPublicKey() method.
An invalid value for the key argument has been passed to the\ncrypto.ECDH() class computeSecret() method. It means that the public\nkey lies outside of the elliptic curve.
An invalid crypto engine identifier was passed to\nrequire('crypto').setEngine().
The --force-fips command-line argument was used but there was an attempt\nto enable or disable FIPS mode in the crypto module.
An attempt was made to enable or disable FIPS mode, but FIPS mode was not\navailable.
\n", "type": "module", "displayName": "ERR_CRYPTO_FIPS_UNAVAILABLE" }, { "textRaw": "ERR_CRYPTO_HASH_DIGEST_NO_UTF16", "name": "err_crypto_hash_digest_no_utf16", "desc": "The UTF-16 encoding was used with hash.digest(). While the\nhash.digest() method does allow an encoding argument to be passed in,\ncausing the method to return a string rather than a Buffer, the UTF-16\nencoding (e.g. ucs or utf16le) is not supported.
hash.digest() was called multiple times. The hash.digest() method must\nbe called no more than one time per instance of a Hash object.
hash.update() failed for any reason. This should rarely, if ever, happen.
The selected public or private key encoding is incompatible with other options.
\n", "type": "module", "displayName": "ERR_CRYPTO_INCOMPATIBLE_KEY_OPTIONS" }, { "textRaw": "ERR_CRYPTO_INVALID_DIGEST", "name": "err_crypto_invalid_digest", "desc": "An invalid crypto digest algorithm was specified.
\n", "type": "module", "displayName": "ERR_CRYPTO_INVALID_DIGEST" }, { "textRaw": "ERR_CRYPTO_INVALID_STATE", "name": "err_crypto_invalid_state", "desc": "A crypto method was used on an object that was in an invalid state. For\ninstance, calling cipher.getAuthTag() before calling cipher.final().
The PBKDF2 algorithm failed for unspecified reasons. OpenSSL does not provide\nmore details and therefore neither does Node.js.
\n", "type": "module", "displayName": "ERR_CRYPTO_PBKDF2_ERROR" }, { "textRaw": "ERR_CRYPTO_SCRYPT_INVALID_PARAMETER", "name": "err_crypto_scrypt_invalid_parameter", "desc": "One or more crypto.scrypt() or crypto.scryptSync() parameters are\noutside their legal range.
Node.js was compiled without scrypt support. Not possible with the official\nrelease binaries but can happen with custom builds, including distro builds.
A signing key was not provided to the sign.sign() method.
crypto.timingSafeEqual() was called with Buffer, TypedArray, or\nDataView arguments of different lengths.
c-ares failed to set the DNS server.
The domain module was not usable since it could not establish the required\nerror handling hooks, because\nprocess.setUncaughtExceptionCaptureCallback() had been called at an\nearlier point in time.
process.setUncaughtExceptionCaptureCallback() could not be called\nbecause the domain module has been loaded at an earlier point in time.
The stack trace is extended to include the point in time at which the\ndomain module had been loaded.
Data provided to util.TextDecoder() API was invalid according to the encoding\nprovided.
Encoding provided to util.TextDecoder() API was not one of the\nWHATWG Supported Encodings.
A Promise that was callbackified via util.callbackify() was rejected with a\nfalsy value.
An attempt has been made to read a file whose size is larger than the maximum\nallowed size for a Buffer.
An invalid symlink type was passed to the fs.symlink() or\nfs.symlinkSync() methods.
An attempt was made to add more headers after the headers had already been sent.
\n", "type": "module", "displayName": "ERR_HTTP_HEADERS_SENT" }, { "textRaw": "ERR_HTTP_INVALID_HEADER_VALUE", "name": "err_http_invalid_header_value", "desc": "An invalid HTTP header value was specified.
\n", "type": "module", "displayName": "ERR_HTTP_INVALID_HEADER_VALUE" }, { "textRaw": "ERR_HTTP_INVALID_STATUS_CODE", "name": "err_http_invalid_status_code", "desc": "Status code was outside the regular status code range (100-999).
\n", "type": "module", "displayName": "ERR_HTTP_INVALID_STATUS_CODE" }, { "textRaw": "ERR_HTTP_TRAILER_INVALID", "name": "err_http_trailer_invalid", "desc": "The Trailer header was set even though the transfer encoding does not support\nthat.
HTTP/2 ALTSVC frames require a valid origin.
\n", "type": "module", "displayName": "ERR_HTTP2_ALTSVC_INVALID_ORIGIN" }, { "textRaw": "ERR_HTTP2_ALTSVC_LENGTH", "name": "err_http2_altsvc_length", "desc": "HTTP/2 ALTSVC frames are limited to a maximum of 16,382 payload bytes.
\n", "type": "module", "displayName": "ERR_HTTP2_ALTSVC_LENGTH" }, { "textRaw": "ERR_HTTP2_CONNECT_AUTHORITY", "name": "err_http2_connect_authority", "desc": "For HTTP/2 requests using the CONNECT method, the :authority pseudo-header\nis required.
For HTTP/2 requests using the CONNECT method, the :path pseudo-header is\nforbidden.
For HTTP/2 requests using the CONNECT method, the :scheme pseudo-header is\nforbidden.
A non-specific HTTP/2 error has occurred.
\n", "type": "module", "displayName": "ERR_HTTP2_ERROR" }, { "textRaw": "ERR_HTTP2_GOAWAY_SESSION", "name": "err_http2_goaway_session", "desc": "New HTTP/2 Streams may not be opened after the Http2Session has received a\nGOAWAY frame from the connected peer.
An additional headers was specified after an HTTP/2 response was initiated.
\n", "type": "module", "displayName": "ERR_HTTP2_HEADERS_AFTER_RESPOND" }, { "textRaw": "ERR_HTTP2_HEADERS_SENT", "name": "err_http2_headers_sent", "desc": "An attempt was made to send multiple response headers.
\n", "type": "module", "displayName": "ERR_HTTP2_HEADERS_SENT" }, { "textRaw": "ERR_HTTP2_HEADER_SINGLE_VALUE", "name": "err_http2_header_single_value", "desc": "Multiple values were provided for an HTTP/2 header field that was required to\nhave only a single value.
\n", "type": "module", "displayName": "ERR_HTTP2_HEADER_SINGLE_VALUE" }, { "textRaw": "ERR_HTTP2_INFO_STATUS_NOT_ALLOWED", "name": "err_http2_info_status_not_allowed", "desc": "Informational HTTP status codes (1xx) may not be set as the response status\ncode on HTTP/2 responses.
HTTP/1 connection specific headers are forbidden to be used in HTTP/2\nrequests and responses.
\n", "type": "module", "displayName": "ERR_HTTP2_INVALID_CONNECTION_HEADERS" }, { "textRaw": "ERR_HTTP2_INVALID_HEADER_VALUE", "name": "err_http2_invalid_header_value", "desc": "An invalid HTTP/2 header value was specified.
\n", "type": "module", "displayName": "ERR_HTTP2_INVALID_HEADER_VALUE" }, { "textRaw": "ERR_HTTP2_INVALID_INFO_STATUS", "name": "err_http2_invalid_info_status", "desc": "An invalid HTTP informational status code has been specified. Informational\nstatus codes must be an integer between 100 and 199 (inclusive).
HTTP/2 ORIGIN frames require a valid origin.
Input Buffer and Uint8Array instances passed to the\nhttp2.getUnpackedSettings() API must have a length that is a multiple of\nsix.
Only valid HTTP/2 pseudoheaders (:status, :path, :authority, :scheme,\nand :method) may be used.
An action was performed on an Http2Session object that had already been\ndestroyed.
An invalid value has been specified for an HTTP/2 setting.
\n", "type": "module", "displayName": "ERR_HTTP2_INVALID_SETTING_VALUE" }, { "textRaw": "ERR_HTTP2_INVALID_STREAM", "name": "err_http2_invalid_stream", "desc": "An operation was performed on a stream that had already been destroyed.
\n", "type": "module", "displayName": "ERR_HTTP2_INVALID_STREAM" }, { "textRaw": "ERR_HTTP2_MAX_PENDING_SETTINGS_ACK", "name": "err_http2_max_pending_settings_ack", "desc": "Whenever an HTTP/2 SETTINGS frame is sent to a connected peer, the peer is\nrequired to send an acknowledgment that it has received and applied the new\nSETTINGS. By default, a maximum number of unacknowledged SETTINGS frames may\nbe sent at any given time. This error code is used when that limit has been\nreached.
An attempt was made to initiate a new push stream from within a push stream.\nNested push streams are not permitted.
\n", "type": "module", "displayName": "ERR_HTTP2_NESTED_PUSH" }, { "textRaw": "ERR_HTTP2_NO_SOCKET_MANIPULATION", "name": "err_http2_no_socket_manipulation", "desc": "An attempt was made to directly manipulate (read, write, pause, resume, etc.) a\nsocket attached to an Http2Session.
HTTP/2 ORIGIN frames are limited to a length of 16382 bytes.
The number of streams created on a single HTTP/2 session reached the maximum\nlimit.
\n", "type": "module", "displayName": "ERR_HTTP2_OUT_OF_STREAMS" }, { "textRaw": "ERR_HTTP2_PAYLOAD_FORBIDDEN", "name": "err_http2_payload_forbidden", "desc": "A message payload was specified for an HTTP response code for which a payload is\nforbidden.
\n", "type": "module", "displayName": "ERR_HTTP2_PAYLOAD_FORBIDDEN" }, { "textRaw": "ERR_HTTP2_PING_CANCEL", "name": "err_http2_ping_cancel", "desc": "An HTTP/2 ping was canceled.
\n", "type": "module", "displayName": "ERR_HTTP2_PING_CANCEL" }, { "textRaw": "ERR_HTTP2_PING_LENGTH", "name": "err_http2_ping_length", "desc": "HTTP/2 ping payloads must be exactly 8 bytes in length.
\n", "type": "module", "displayName": "ERR_HTTP2_PING_LENGTH" }, { "textRaw": "ERR_HTTP2_PSEUDOHEADER_NOT_ALLOWED", "name": "err_http2_pseudoheader_not_allowed", "desc": "An HTTP/2 pseudo-header has been used inappropriately. Pseudo-headers are header\nkey names that begin with the : prefix.
An attempt was made to create a push stream, which had been disabled by the\nclient.
\n", "type": "module", "displayName": "ERR_HTTP2_PUSH_DISABLED" }, { "textRaw": "ERR_HTTP2_SEND_FILE", "name": "err_http2_send_file", "desc": "An attempt was made to use the Http2Stream.prototype.responseWithFile() API to\nsend a directory.
An attempt was made to use the Http2Stream.prototype.responseWithFile() API to\nsend something other than a regular file, but offset or length options were\nprovided.
The Http2Session closed with a non-zero error code.
The Http2Session settings canceled.
An attempt was made to connect a Http2Session object to a net.Socket or\ntls.TLSSocket that had already been bound to another Http2Session object.
An attempt was made to use the socket property of an Http2Session that\nhas already been closed.
Use of the 101 Informational status code is forbidden in HTTP/2.
An invalid HTTP status code has been specified. Status codes must be an integer\nbetween 100 and 599 (inclusive).
An Http2Stream was destroyed before any data was transmitted to the connected\npeer.
A non-zero error code was been specified in an RST_STREAM frame.
When setting the priority for an HTTP/2 stream, the stream may be marked as\na dependency for a parent stream. This error code is used when an attempt is\nmade to mark a stream and dependent of itself.
\n", "type": "module", "displayName": "ERR_HTTP2_STREAM_SELF_DEPENDENCY" }, { "textRaw": "ERR_HTTP2_TRAILERS_ALREADY_SENT", "name": "err_http2_trailers_already_sent", "desc": "Trailing headers have already been sent on the Http2Stream.
The http2stream.sendTrailers() method cannot be called until after the\n'wantTrailers' event is emitted on an Http2Stream object. The\n'wantTrailers' event will only be emitted if the waitForTrailers option\nis set for the Http2Stream.
http2.connect() was passed a URL that uses any protocol other than http: or\nhttps:.
A given index was out of the accepted range (e.g. negative offsets).
\n", "type": "module", "displayName": "ERR_INDEX_OUT_OF_RANGE" }, { "textRaw": "ERR_INSPECTOR_ALREADY_CONNECTED", "name": "err_inspector_already_connected", "desc": "While using the inspector module, an attempt was made to connect when the\ninspector was already connected.
While using the inspector module, an attempt was made to use the inspector\nafter the session had already closed.
The inspector module is not available for use.
While using the inspector module, an attempt was made to use the inspector\nbefore it was connected.
The provided address family is not understood by the Node.js API.
\n", "type": "module", "displayName": "ERR_INVALID_ADDRESS_FAMILY" }, { "textRaw": "ERR_INVALID_ARG_TYPE", "name": "err_invalid_arg_type", "desc": "An argument of the wrong type was passed to a Node.js API.
\n", "type": "module", "displayName": "ERR_INVALID_ARG_TYPE" }, { "textRaw": "ERR_INVALID_ARG_VALUE", "name": "err_invalid_arg_value", "desc": "An invalid or unsupported value was passed for a given argument.
\n", "type": "module", "displayName": "ERR_INVALID_ARG_VALUE" }, { "textRaw": "ERR_INVALID_ARRAY_LENGTH", "name": "err_invalid_array_length", "desc": "An array was not of the expected length or in a valid range.
\n", "type": "module", "displayName": "ERR_INVALID_ARRAY_LENGTH" }, { "textRaw": "ERR_INVALID_ASYNC_ID", "name": "err_invalid_async_id", "desc": "An invalid asyncId or triggerAsyncId was passed using AsyncHooks. An id\nless than -1 should never happen.
A swap was performed on a Buffer but its size was not compatible with the\noperation.
A callback function was required but was not been provided to a Node.js API.
\n", "type": "module", "displayName": "ERR_INVALID_CALLBACK" }, { "textRaw": "ERR_INVALID_CHAR", "name": "err_invalid_char", "desc": "Invalid characters were detected in headers.
\n", "type": "module", "displayName": "ERR_INVALID_CHAR" }, { "textRaw": "ERR_INVALID_CURSOR_POS", "name": "err_invalid_cursor_pos", "desc": "A cursor on a given stream cannot be moved to a specified row without a\nspecified column.
\n", "type": "module", "displayName": "ERR_INVALID_CURSOR_POS" }, { "textRaw": "ERR_INVALID_DOMAIN_NAME", "name": "err_invalid_domain_name", "desc": "hostname can not be parsed from a provided URL.
A file descriptor ('fd') was not valid (e.g. it was a negative value).
\n", "type": "module", "displayName": "ERR_INVALID_FD" }, { "textRaw": "ERR_INVALID_FD_TYPE", "name": "err_invalid_fd_type", "desc": "A file descriptor ('fd') type was not valid.
\n", "type": "module", "displayName": "ERR_INVALID_FD_TYPE" }, { "textRaw": "ERR_INVALID_FILE_URL_HOST", "name": "err_invalid_file_url_host", "desc": "A Node.js API that consumes file: URLs (such as certain functions in the\nfs module) encountered a file URL with an incompatible host. This\nsituation can only occur on Unix-like systems where only localhost or an empty\nhost is supported.
A Node.js API that consumes file: URLs (such as certain functions in the\nfs module) encountered a file URL with an incompatible path. The exact\nsemantics for determining whether a path can be used is platform-dependent.
An attempt was made to send an unsupported \"handle\" over an IPC communication\nchannel to a child process. See subprocess.send() and process.send() for\nmore information.
An invalid HTTP token was supplied.
\n", "type": "module", "displayName": "ERR_INVALID_HTTP_TOKEN" }, { "textRaw": "ERR_INVALID_IP_ADDRESS", "name": "err_invalid_ip_address", "desc": "An IP address is not valid.
\n", "type": "module", "displayName": "ERR_INVALID_IP_ADDRESS" }, { "textRaw": "ERR_INVALID_OPT_VALUE", "name": "err_invalid_opt_value", "desc": "An invalid or unexpected value was passed in an options object.
\n", "type": "module", "displayName": "ERR_INVALID_OPT_VALUE" }, { "textRaw": "ERR_INVALID_OPT_VALUE_ENCODING", "name": "err_invalid_opt_value_encoding", "desc": "An invalid or unknown file encoding was passed.
\n", "type": "module", "displayName": "ERR_INVALID_OPT_VALUE_ENCODING" }, { "textRaw": "ERR_INVALID_PERFORMANCE_MARK", "name": "err_invalid_performance_mark", "desc": "While using the Performance Timing API (perf_hooks), a performance mark is\ninvalid.
An invalid options.protocol was passed.
Both breakEvalOnSigint and eval options were set in the REPL config, which\nis not supported.
Thrown in case a function option does not provide a valid value for one of its\nreturned object properties on execution.
\n", "type": "module", "displayName": "ERR_INVALID_RETURN_PROPERTY" }, { "textRaw": "ERR_INVALID_RETURN_PROPERTY_VALUE", "name": "err_invalid_return_property_value", "desc": "Thrown in case a function option does not provide an expected value\ntype for one of its returned object properties on execution.
\n", "type": "module", "displayName": "ERR_INVALID_RETURN_PROPERTY_VALUE" }, { "textRaw": "ERR_INVALID_RETURN_VALUE", "name": "err_invalid_return_value", "desc": "Thrown in case a function option does not return an expected value\ntype on execution, such as when a function is expected to return a promise.
\n", "type": "module", "displayName": "ERR_INVALID_RETURN_VALUE" }, { "textRaw": "ERR_INVALID_SYNC_FORK_INPUT", "name": "err_invalid_sync_fork_input", "desc": "A Buffer, TypedArray, DataView or string was provided as stdio input to\nan asynchronous fork. See the documentation for the child_process module\nfor more information.
A Node.js API function was called with an incompatible this value.
const urlSearchParams = new URLSearchParams('foo=bar&baz=new');\n\nconst buf = Buffer.alloc(1);\nurlSearchParams.has.call(buf, 'foo');\n// Throws a TypeError with code 'ERR_INVALID_THIS'\nAn invalid transfer object was passed to postMessage().
An element in the iterable provided to the WHATWG\nURLSearchParams constructor did not\nrepresent a [name, value] tuple – that is, if an element is not iterable, or\ndoes not consist of exactly two elements.
An invalid URI was passed.
\n", "type": "module", "displayName": "ERR_INVALID_URI" }, { "textRaw": "ERR_INVALID_URL", "name": "err_invalid_url", "desc": "An invalid URL was passed to the WHATWG\nURL constructor to be parsed. The thrown error object\ntypically has an additional property 'input' that contains the URL that failed\nto parse.
An attempt was made to use a URL of an incompatible scheme (protocol) for a\nspecific purpose. It is only used in the WHATWG URL API support in the\nfs module (which only accepts URLs with 'file' scheme), but may be used\nin other Node.js APIs as well in the future.
An attempt was made to use an IPC communication channel that was already closed.
\n", "type": "module", "displayName": "ERR_IPC_CHANNEL_CLOSED" }, { "textRaw": "ERR_IPC_DISCONNECTED", "name": "err_ipc_disconnected", "desc": "An attempt was made to disconnect an IPC communication channel that was already\ndisconnected. See the documentation for the child_process module\nfor more information.
An attempt was made to create a child Node.js process using more than one IPC\ncommunication channel. See the documentation for the child_process module\nfor more information.
An attempt was made to open an IPC communication channel with a synchronously\nforked Node.js process. See the documentation for the child_process module\nfor more information.
An attempt was made to allocate memory (usually in the C++ layer) but it\nfailed.
\n", "type": "module", "displayName": "ERR_MEMORY_ALLOCATION_FAILED" }, { "textRaw": "ERR_METHOD_NOT_IMPLEMENTED", "name": "err_method_not_implemented", "desc": "A method is required but not implemented.
\n", "type": "module", "displayName": "ERR_METHOD_NOT_IMPLEMENTED" }, { "textRaw": "ERR_MISSING_ARGS", "name": "err_missing_args", "desc": "A required argument of a Node.js API was not passed. This is only used for\nstrict compliance with the API specification (which in some cases may accept\nfunc(undefined) but not func()). In most native Node.js APIs,\nfunc(undefined) and func() are treated identically, and the\nERR_INVALID_ARG_TYPE error code may be used instead.
An ES6 module loader hook specified format: 'dynamic' but did not provide\na dynamicInstantiate hook.
A MessagePort was found in the object passed to a postMessage() call,\nbut not provided in the transferList for that call.
An ES6 module could not be resolved.
\n", "type": "module", "displayName": "ERR_MISSING_MODULE" }, { "textRaw": "ERR_MISSING_PLATFORM_FOR_WORKER", "name": "err_missing_platform_for_worker", "desc": "The V8 platform used by this instance of Node.js does not support creating\nWorkers. This is caused by lack of embedder support for Workers. In particular,\nthis error will not occur with standard builds of Node.js.
\n", "type": "module", "displayName": "ERR_MISSING_PLATFORM_FOR_WORKER" }, { "textRaw": "ERR_MODULE_RESOLUTION_LEGACY", "name": "err_module_resolution_legacy", "stability": 1, "stabilityText": "Experimental", "desc": "A failure occurred resolving imports in an ES6 module.
\n", "type": "module", "displayName": "ERR_MODULE_RESOLUTION_LEGACY" }, { "textRaw": "ERR_MULTIPLE_CALLBACK", "name": "err_multiple_callback", "desc": "A callback was called more than once.
\nA callback is almost always meant to only be called once as the query\ncan either be fulfilled or rejected but not both at the same time. The latter\nwould be possible by calling a callback more than once.
\n", "type": "module", "displayName": "ERR_MULTIPLE_CALLBACK" }, { "textRaw": "ERR_NAPI_CONS_FUNCTION", "name": "err_napi_cons_function", "desc": "While using N-API, a constructor passed was not a function.
While calling napi_create_dataview(), a given offset was outside the bounds\nof the dataview or offset + length was larger than a length of given buffer.
While calling napi_create_typedarray(), the provided offset was not a\nmultiple of the element size.
While calling napi_create_typedarray(), (length * size_of_element) + byte_offset was larger than the length of given buffer.
An error occurred while invoking the JavaScript portion of the thread-safe\nfunction.
\n", "type": "module", "displayName": "ERR_NAPI_TSFN_CALL_JS" }, { "textRaw": "ERR_NAPI_TSFN_GET_UNDEFINED", "name": "err_napi_tsfn_get_undefined", "desc": "An error occurred while attempting to retrieve the JavaScript undefined\nvalue.
On the main thread, values are removed from the queue associated with the\nthread-safe function in an idle loop. This error indicates that an error\nhas occurred when attempting to start the loop.
\n", "type": "module", "displayName": "ERR_NAPI_TSFN_START_IDLE_LOOP" }, { "textRaw": "ERR_NAPI_TSFN_STOP_IDLE_LOOP", "name": "err_napi_tsfn_stop_idle_loop", "desc": "Once no more items are left in the queue, the idle loop must be suspended. This\nerror indicates that the idle loop has failed to stop.
\n", "type": "module", "displayName": "ERR_NAPI_TSFN_STOP_IDLE_LOOP" }, { "textRaw": "ERR_NO_CRYPTO", "name": "err_no_crypto", "desc": "An attempt was made to use crypto features while Node.js was not compiled with\nOpenSSL crypto support.
\n", "type": "module", "displayName": "ERR_NO_CRYPTO" }, { "textRaw": "ERR_NO_ICU", "name": "err_no_icu", "desc": "An attempt was made to use features that require ICU, but Node.js was not\ncompiled with ICU support.
\n", "type": "module", "displayName": "ERR_NO_ICU" }, { "textRaw": "ERR_NO_LONGER_SUPPORTED", "name": "err_no_longer_supported", "desc": "A Node.js API was called in an unsupported manner, such as\nBuffer.write(string, encoding, offset[, length]).
A given value is out of the accepted range.
\n", "type": "module", "displayName": "ERR_OUT_OF_RANGE" }, { "textRaw": "ERR_REQUIRE_ESM", "name": "err_require_esm", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to require() an ES6 module.
Script execution was interrupted by SIGINT (For example, when Ctrl+C was\npressed).
The server.listen() method was called while a net.Server was already\nlistening. This applies to all instances of net.Server, including HTTP, HTTPS,\nand HTTP/2 Server instances.
The server.close() method was called when a net.Server was not\nrunning. This applies to all instances of net.Server, including HTTP, HTTPS,\nand HTTP/2 Server instances.
An attempt was made to bind a socket that has already been bound.
\n", "type": "module", "displayName": "ERR_SOCKET_ALREADY_BOUND" }, { "textRaw": "ERR_SOCKET_BAD_BUFFER_SIZE", "name": "err_socket_bad_buffer_size", "desc": "An invalid (negative) size was passed for either the recvBufferSize or\nsendBufferSize options in dgram.createSocket().
An API function expecting a port >= 0 and < 65536 received an invalid value.
\n", "type": "module", "displayName": "ERR_SOCKET_BAD_PORT" }, { "textRaw": "ERR_SOCKET_BAD_TYPE", "name": "err_socket_bad_type", "desc": "An API function expecting a socket type (udp4 or udp6) received an invalid\nvalue.
While using dgram.createSocket(), the size of the receive or send Buffer\ncould not be determined.
Data could be sent on a socket.
\n", "type": "module", "displayName": "ERR_SOCKET_CANNOT_SEND" }, { "textRaw": "ERR_SOCKET_CLOSED", "name": "err_socket_closed", "desc": "An attempt was made to operate on an already closed socket.
\n", "type": "module", "displayName": "ERR_SOCKET_CLOSED" }, { "textRaw": "ERR_SOCKET_DGRAM_NOT_RUNNING", "name": "err_socket_dgram_not_running", "desc": "A call was made and the UDP subsystem was not running.
\n", "type": "module", "displayName": "ERR_SOCKET_DGRAM_NOT_RUNNING" }, { "textRaw": "ERR_STREAM_CANNOT_PIPE", "name": "err_stream_cannot_pipe", "desc": "An attempt was made to call stream.pipe() on a Writable stream.
A stream method was called that cannot complete because the stream was\ndestroyed using stream.destroy().
An attempt was made to call stream.write() with a null chunk.
An error returned by stream.finished() and stream.pipeline(), when a stream\nor a pipeline ends non gracefully with no explicit error.
An attempt was made to call stream.push() after a null(EOF) had been\npushed to the stream.
An attempt was made to call stream.unshift() after the 'end' event was\nemitted.
Prevents an abort if a string decoder was set on the Socket or if the decoder\nis in objectMode.
const Socket = require('net').Socket;\nconst instance = new Socket();\n\ninstance.setEncoding('utf8');\nAn attempt was made to call stream.write() after stream.end() has been\ncalled.
An attempt has been made to create a string longer than the maximum allowed\nlength.
\n", "type": "module", "displayName": "ERR_STRING_TOO_LONG" }, { "textRaw": "ERR_SYSTEM_ERROR", "name": "err_system_error", "desc": "An unspecified or non-specific system error has occurred within the Node.js\nprocess. The error object will have an err.info object property with\nadditional details.
While using TLS, the hostname/IP of the peer did not match any of the\nsubjectAltNames in its certificate.
While using TLS, the parameter offered for the Diffie-Hellman (DH)\nkey-agreement protocol is too small. By default, the key length must be greater\nthan or equal to 1024 bits to avoid vulnerabilities, even though it is strongly\nrecommended to use 2048 bits or larger for stronger security.
A TLS/SSL handshake timed out. In this case, the server must also abort the\nconnection.
\n", "type": "module", "displayName": "ERR_TLS_HANDSHAKE_TIMEOUT" }, { "textRaw": "ERR_TLS_INVALID_PROTOCOL_VERSION", "name": "err_tls_invalid_protocol_version", "desc": "Valid TLS protocol versions are 'TLSv1', 'TLSv1.1', or 'TLSv1.2'.
Attempting to set a TLS protocol minVersion or maxVersion conflicts with an\nattempt to set the secureProtocol explicitly. Use one mechanism or the other.
An attempt to renegotiate the TLS session failed.
\n", "type": "module", "displayName": "ERR_TLS_RENEGOTIATE" }, { "textRaw": "ERR_TLS_RENEGOTIATION_DISABLED", "name": "err_tls_renegotiation_disabled", "desc": "An attempt was made to renegotiate TLS on a socket instance with TLS disabled.
\n", "type": "module", "displayName": "ERR_TLS_RENEGOTIATION_DISABLED" }, { "textRaw": "ERR_TLS_REQUIRED_SERVER_NAME", "name": "err_tls_required_server_name", "desc": "While using TLS, the server.addContext() method was called without providing\na hostname in the first parameter.
An excessive amount of TLS renegotiations is detected, which is a potential\nvector for denial-of-service attacks.
\n", "type": "module", "displayName": "ERR_TLS_SESSION_ATTACK" }, { "textRaw": "ERR_TLS_SNI_FROM_SERVER", "name": "err_tls_sni_from_server", "desc": "An attempt was made to issue Server Name Indication from a TLS server-side\nsocket, which is only valid from a client.
\n", "type": "module", "displayName": "ERR_TLS_SNI_FROM_SERVER" }, { "textRaw": "ERR_TRACE_EVENTS_CATEGORY_REQUIRED", "name": "err_trace_events_category_required", "desc": "The trace_events.createTracing() method requires at least one trace event\ncategory.
The trace_events module could not be loaded because Node.js was compiled with\nthe --without-v8-platform flag.
A SharedArrayBuffer whose memory is not managed by the JavaScript engine\nor by Node.js was encountered during serialization. Such a SharedArrayBuffer\ncannot be serialized.
This can only happen when native addons create SharedArrayBuffers in\n\"externalized\" mode, or put existing SharedArrayBuffer into externalized mode.
A Transform stream finished while it was still transforming.
A Transform stream finished with data still in the write buffer.
The initialization of a TTY failed due to a system error.
\n", "type": "module", "displayName": "ERR_TTY_INIT_FAILED" }, { "textRaw": "ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET", "name": "err_uncaught_exception_capture_already_set", "desc": "process.setUncaughtExceptionCaptureCallback() was called twice,\nwithout first resetting the callback to null.
This error is designed to prevent accidentally overwriting a callback registered\nfrom another module.
\n", "type": "module", "displayName": "ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET" }, { "textRaw": "ERR_UNESCAPED_CHARACTERS", "name": "err_unescaped_characters", "desc": "A string that contained unescaped characters was received.
\n", "type": "module", "displayName": "ERR_UNESCAPED_CHARACTERS" }, { "textRaw": "ERR_UNHANDLED_ERROR", "name": "err_unhandled_error", "desc": "An unhandled error occurred (for instance, when an 'error' event is emitted\nby an EventEmitter but an 'error' handler is not registered).
Used to identify a specific kind of internal Node.js error that should not\ntypically be triggered by user code. Instances of this error point to an\ninternal bug within the Node.js binary itself.
\n", "type": "module", "displayName": "ERR_UNKNOWN_BUILTIN_MODULE" }, { "textRaw": "ERR_UNKNOWN_ENCODING", "name": "err_unknown_encoding", "desc": "An invalid or unknown encoding option was passed to an API.
\n", "type": "module", "displayName": "ERR_UNKNOWN_ENCODING" }, { "textRaw": "ERR_UNKNOWN_FILE_EXTENSION", "name": "err_unknown_file_extension", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to load a module with an unknown or unsupported file\nextension.
\n", "type": "module", "displayName": "ERR_UNKNOWN_FILE_EXTENSION" }, { "textRaw": "ERR_UNKNOWN_MODULE_FORMAT", "name": "err_unknown_module_format", "stability": 1, "stabilityText": "Experimental", "desc": "An attempt was made to load a module with an unknown or unsupported format.
\n", "type": "module", "displayName": "ERR_UNKNOWN_MODULE_FORMAT" }, { "textRaw": "ERR_UNKNOWN_SIGNAL", "name": "err_unknown_signal", "desc": "An invalid or unknown process signal was passed to an API expecting a valid\nsignal (such as subprocess.kill()).
An attempt was made to launch a Node.js process with an unknown stdin file\ntype. This error is usually an indication of a bug within Node.js itself,\nalthough it is possible for user code to trigger it.
An attempt was made to launch a Node.js process with an unknown stdout or\nstderr file type. This error is usually an indication of a bug within Node.js\nitself, although it is possible for user code to trigger it.
The V8 BreakIterator API was used but the full ICU data set is not installed.
While using the Performance Timing API (perf_hooks), no valid performance\nentry types were found.
A dynamic import callback was not specified.
\n", "type": "module", "displayName": "ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING" }, { "textRaw": "ERR_VM_MODULE_ALREADY_LINKED", "name": "err_vm_module_already_linked", "desc": "The module attempted to be linked is not eligible for linking, because of one of\nthe following reasons:
\nlinkingStatus is 'linked')linkingStatus is 'linking')linkingStatus is 'errored')The module being returned from the linker function is from a different context\nthan the parent module. Linked modules must share the same context.
\n", "type": "module", "displayName": "ERR_VM_MODULE_DIFFERENT_CONTEXT" }, { "textRaw": "ERR_VM_MODULE_LINKING_ERRORED", "name": "err_vm_module_linking_errored", "desc": "The linker function returned a module for which linking has failed.
\n", "type": "module", "displayName": "ERR_VM_MODULE_LINKING_ERRORED" }, { "textRaw": "ERR_VM_MODULE_NOT_LINKED", "name": "err_vm_module_not_linked", "desc": "The module must be successfully linked before instantiation.
\n", "type": "module", "displayName": "ERR_VM_MODULE_NOT_LINKED" }, { "textRaw": "ERR_VM_MODULE_NOT_MODULE", "name": "err_vm_module_not_module", "desc": "The fulfilled value of a linking promise is not a vm.SourceTextModule object.
The current module's status does not allow for this operation. The specific\nmeaning of the error depends on the specific function.
\n", "type": "module", "displayName": "ERR_VM_MODULE_STATUS" }, { "textRaw": "ERR_WORKER_PATH", "name": "err_worker_path", "desc": "The path for the main script of a worker is neither an absolute path\nnor a relative path starting with ./ or ../.
All attempts at serializing an uncaught exception from a worker thread failed.
\n", "type": "module", "displayName": "ERR_WORKER_UNSERIALIZABLE_ERROR" }, { "textRaw": "ERR_WORKER_UNSUPPORTED_EXTENSION", "name": "err_worker_unsupported_extension", "desc": "The pathname used for the main script of a worker has an\nunknown file extension.
\n", "type": "module", "displayName": "ERR_WORKER_UNSUPPORTED_EXTENSION" }, { "textRaw": "ERR_ZLIB_INITIALIZATION_FAILED", "name": "err_zlib_initialization_failed", "desc": "Creation of a zlib object failed due to incorrect configuration.
Too much HTTP header data was received. In order to protect against malicious or\nmalconfigured clients, if more than 8KB of HTTP header data is received then\nHTTP parsing will abort without a request or response object being created, and\nan Error with this code will be emitted.
A module file could not be resolved while attempting a require() or\nimport operation.
Used when a failure occurs sending an individual frame on the HTTP/2\nsession.
\n", "type": "module", "displayName": "ERR_HTTP2_FRAME_ERROR" }, { "textRaw": "ERR_HTTP2_HEADERS_OBJECT", "name": "err_http2_headers_object", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an HTTP/2 Headers Object is expected.
\n", "type": "module", "displayName": "ERR_HTTP2_HEADERS_OBJECT" }, { "textRaw": "ERR_HTTP2_HEADER_REQUIRED", "name": "err_http2_header_required", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when a required header is missing in an HTTP/2 message.
\n", "type": "module", "displayName": "ERR_HTTP2_HEADER_REQUIRED" }, { "textRaw": "ERR_HTTP2_INFO_HEADERS_AFTER_RESPOND", "name": "err_http2_info_headers_after_respond", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "HTTP/2 informational headers must only be sent prior to calling the\nHttp2Stream.prototype.respond() method.
Used when an action has been performed on an HTTP/2 Stream that has already\nbeen closed.
\n", "type": "module", "displayName": "ERR_HTTP2_STREAM_CLOSED" }, { "textRaw": "ERR_HTTP_INVALID_CHAR", "name": "err_http_invalid_char", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an invalid character is found in an HTTP response status message\n(reason phrase).
\n", "type": "module", "displayName": "ERR_HTTP_INVALID_CHAR" }, { "textRaw": "ERR_NAPI_CONS_PROTOTYPE_OBJECT", "name": "err_napi_cons_prototype_object", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used by the N-API when Constructor.prototype is not an object.
Used generically to identify that an operation caused an out of memory\ncondition.
\n", "type": "module", "displayName": "ERR_OUTOFMEMORY" }, { "textRaw": "ERR_PARSE_HISTORY_DATA", "name": "err_parse_history_data", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "The repl module was unable to parse data from the REPL history file.
An attempt was made to close the process.stderr stream. By design, Node.js\ndoes not allow stdout or stderr streams to be closed by user code.
An attempt was made to close the process.stdout stream. By design, Node.js\ndoes not allow stdout or stderr streams to be closed by user code.
Used when an attempt is made to use a readable stream that has not implemented\nreadable._read().
Used when a TLS renegotiation request has failed in a non-specific way.
\n", "type": "module", "displayName": "ERR_TLS_RENEGOTIATION_FAILED" }, { "textRaw": "ERR_UNKNOWN_BUILTIN_MODULE", "name": "err_unknown_builtin_module", "meta": { "added": [ "v8.0.0" ], "removed": [ "v9.0.0" ], "changes": [] }, "desc": "The 'ERR_UNKNOWN_BUILTIN_MODULE' error code is used to identify a specific\nkind of internal Node.js error that should not typically be triggered by user\ncode. Instances of this error point to an internal bug within the Node.js\nbinary itself.
Used when a given value is out of the accepted range.
\n", "type": "module", "displayName": "ERR_VALUE_OUT_OF_RANGE" }, { "textRaw": "ERR_ZLIB_BINDING_CLOSED", "name": "err_zlib_binding_closed", "meta": { "added": [ "v9.0.0" ], "removed": [ "v10.0.0" ], "changes": [] }, "desc": "Used when an attempt is made to use a zlib object after it has already been\nclosed.
These errors have never been released, but had been present on master between\nreleases.
\n", "modules": [ { "textRaw": "ERR_FS_WATCHER_ALREADY_STARTED", "name": "err_fs_watcher_already_started", "desc": "An attempt was made to start a watcher returned by fs.watch() that has\nalready been started.
An attempt was made to initiate operations on a watcher returned by\nfs.watch() that has not yet been started.
Occurs with multiple attempts to shutdown an HTTP/2 session.
\n", "type": "module", "displayName": "ERR_HTTP2_ALREADY_SHUTDOWN" }, { "textRaw": "ERR_HTTP2_ERROR", "name": "err_http2_error", "desc": "A non-specific HTTP/2 error has occurred.
\n", "type": "module", "displayName": "ERR_HTTP2_ERROR" }, { "textRaw": "ERR_INVALID_REPL_HISTORY", "name": "err_invalid_repl_history", "desc": "Used in the repl in case the old history file is used and an error occurred\nwhile trying to read and parse it.
Used when an ES6 module loader hook specifies format: 'dynamic' but does\nnot provide a dynamicInstantiate hook.
Used to prevent an abort if a string decoder was set on the Socket.
\nconst Socket = require('net').Socket;\nconst instance = new Socket();\n\ninstance.setEncoding('utf8');\nAn attempt has been made to create a string larger than the maximum allowed\nsize.
", "type": "module", "displayName": "ERR_STRING_TOO_LARGE" } ], "type": "module", "displayName": "Other error codes" } ], "type": "misc", "displayName": "Legacy Node.js Error Codes" } ], "classes": [ { "textRaw": "Class: Error", "type": "class", "name": "Error", "desc": "A generic JavaScript Error object that does not denote any specific\ncircumstance of why the error occurred. Error objects capture a \"stack trace\"\ndetailing the point in the code at which the Error was instantiated, and may\nprovide a text description of the error.
For crypto only, Error objects will include the OpenSSL error stack in a\nseparate property called opensslErrorStack if it is available when the error\nis thrown.
All errors generated by Node.js, including all System and JavaScript errors,\nwill either be instances of, or inherit from, the Error class.
Creates a .stack property on targetObject, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace() was called.
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack; // similar to `new Error().stack`\nThe first line of the trace will be prefixed with\n${myObject.name}: ${myObject.message}.
The optional constructorOpt argument accepts a function. If given, all frames\nabove constructorOpt, including constructorOpt, will be omitted from the\ngenerated stack trace.
The constructorOpt argument is useful for hiding implementation\ndetails of error generation from an end user. For instance:
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would show up in the .stack property. By passing\n// the constructor, we omit that frame, and retain all frames below it.\nnew MyError().stack;\nThe Error.stackTraceLimit property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack or\nError.captureStackTrace(obj)).
The default value is 10 but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.
" }, { "textRaw": "`code` {string}", "type": "string", "name": "code", "desc": "The error.code property is a string label that identifies the kind of error.\nerror.code is the most stable way to identify an error. It will only change\nbetween major versions of Node.js. In contrast, error.message strings may\nchange between any versions of Node.js. See Node.js Error Codes for details\nabout specific codes.
The error.message property is the string description of the error as set by\ncalling new Error(message). The message passed to the constructor will also\nappear in the first line of the stack trace of the Error, however changing\nthis property after the Error object is created may not change the first\nline of the stack trace (for example, when error.stack is read before this\nproperty is changed).
const err = new Error('The message');\nconsole.error(err.message);\n// Prints: The message\nThe error.stack property is a string describing the point in the code at which\nthe Error was instantiated.
Error: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)\nThe first line is formatted as <error class name>: <error message>, and\nis followed by a series of stack frames (each line beginning with \"at \").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.
Frames are only generated for JavaScript functions. If, for example, execution\nsynchronously passes through a C++ addon function called cheetahify which\nitself calls a JavaScript function, the frame representing the cheetahify call\nwill not be present in the stack traces:
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // cheetahify *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster();\n// will throw:\n// /home/gbusey/file.js:6\n// throw new Error('oh no!');\n// ^\n// Error: oh no!\n// at speedy (/home/gbusey/file.js:6:11)\n// at makeFaster (/home/gbusey/file.js:5:3)\n// at Object.<anonymous> (/home/gbusey/file.js:10:1)\n// at Module._compile (module.js:456:26)\n// at Object.Module._extensions..js (module.js:474:10)\n// at Module.load (module.js:356:32)\n// at Function.Module._load (module.js:312:12)\n// at Function.Module.runMain (module.js:497:10)\n// at startup (node.js:119:16)\n// at node.js:906:3\nThe location information will be one of:
\nnative, if the frame represents a call internal to V8 (as in [].forEach).plain-filename.js:line:column, if the frame represents a call internal\nto Node.js./absolute/path/to/file.js:line:column, if the frame represents a call in\na user program, or its dependencies.The string representing the stack trace is lazily generated when the\nerror.stack property is accessed.
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit or the number of available frames on the current event\nloop tick.
System-level errors are generated as augmented Error instances, which are\ndetailed here.
Creates a new Error object and sets the error.message property to the\nprovided text message. If an object is passed as message, the text message\nis generated by calling message.toString(). The error.stack property will\nrepresent the point in the code at which new Error() was called. Stack traces\nare dependent on V8's stack trace API. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit, whichever is smaller.
A subclass of Error that indicates the failure of an assertion. For details,\nsee Class: assert.AssertionError.
A subclass of Error that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.
require('net').connect(-1);\n// throws \"RangeError: \"port\" option should be >= 0 and < 65536: -1\"\nNode.js will generate and throw RangeError instances immediately as a form\nof argument validation.
A subclass of Error that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.
While client code may generate and propagate these errors, in practice, only V8\nwill do so.
\ndoesNotExist;\n// throws ReferenceError, doesNotExist is not a variable in this program.\nUnless an application is dynamically generating and running code,\nReferenceError instances should always be considered a bug in the code\nor its dependencies.
A subclass of Error that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval, Function,\nrequire, or vm. These errors are almost always indicative of a broken\nprogram.
try {\n require('vm').runInThisContext('binary ! isNotOk');\n} catch (err) {\n // err will be a SyntaxError\n}\nSyntaxError instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.
A subclass of Error that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError.
require('url').parse(() => { });\n// throws TypeError, since it expected a string\nNode.js will generate and throw TypeError instances immediately as a form\nof argument validation.
These objects are available in all modules. The following variables may appear\nto be global but are not. They exist only in the scope of modules, see the\nmodule system documentation:
\n__dirname__filenameexportsmodulerequire()The objects listed here are specific to Node.js. There are a number of\nbuilt-in objects that are part of the JavaScript language itself, which are\nalso globally accessible.
", "globals": [ { "textRaw": "Class: Buffer", "type": "global", "name": "Buffer", "meta": { "added": [ "v0.1.103" ], "changes": [] }, "desc": "Used to handle binary data. See the buffer section.
" }, { "textRaw": "clearImmediate(immediateObject)", "type": "global", "name": "clearImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "desc": "clearImmediate is described in the timers section.
clearInterval is described in the timers section.
clearTimeout is described in the timers section.
Used to print to stdout and stderr. See the console section.
In browsers, the top-level scope is the global scope. This means that\nwithin the browser var something will define a new global variable. In\nNode.js this is different. The top-level scope is not the global scope;\nvar something inside a Node.js module will be local to that module.
The process object. See the process object section.
setImmediate is described in the timers section.
setInterval is described in the timers section.
setTimeout is described in the timers section.
The WHATWG URL class. See the URL section.
The WHATWG URLSearchParams class. See the URLSearchParams section.
The object that acts as the namespace for all W3C\nWebAssembly related functionality. See the\nMozilla Developer Network for usage and compatibility.
" } ], "miscs": [ { "textRaw": "__dirname", "name": "__dirname", "desc": "This variable may appear to be global but is not. See __dirname.
This variable may appear to be global but is not. See __filename.
This variable may appear to be global but is not. See exports.
This variable may appear to be global but is not. See module.
This variable may appear to be global but is not. See require().
Node.js has many features that make it easier to write internationalized\nprograms. Some of them are:
\nLocale-sensitive or Unicode-aware functions in the ECMAScript Language\nSpecification:
\n\nAll functionality described in the ECMAScript Internationalization API\nSpecification (aka ECMA-402):
\nIntl objectString.prototype.localeCompare() and\nDate.prototype.toLocaleString()require('buffer').transcode()require('util').TextDecoderRegExp Unicode Property EscapesNode.js (and its underlying V8 engine) uses ICU to implement these features\nin native C/C++ code. However, some of them require a very large ICU data file\nin order to support all locales of the world. Because it is expected that most\nNode.js users will make use of only a small portion of ICU functionality, only\na subset of the full ICU data set is provided by Node.js by default. Several\noptions are provided for customizing and expanding the ICU data set either when\nbuilding or running Node.js.
", "miscs": [ { "textRaw": "Options for building Node.js", "name": "options_for_building_node.js", "desc": "To control how ICU is used in Node.js, four configure options are available\nduring compilation. Additional details on how to compile Node.js are documented\nin BUILDING.md.
--with-intl=none/--without-intl--with-intl=system-icu--with-intl=small-icu (default)--with-intl=full-icuAn overview of available Node.js and JavaScript features for each configure\noption:
| \n | none | \nsystem-icu | \nsmall-icu | \nfull-icu | \n
|---|---|---|---|---|
String.prototype.normalize() | \nnone (function is no-op) | \nfull | \nfull | \nfull | \n
String.prototype.to*Case() | \nfull | \nfull | \nfull | \nfull | \n
Intl | \nnone (object does not exist) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
String.prototype.localeCompare() | \npartial (not locale-aware) | \nfull | \nfull | \nfull | \n
String.prototype.toLocale*Case() | \npartial (not locale-aware) | \nfull | \nfull | \nfull | \n
Number.prototype.toLocaleString() | \npartial (not locale-aware) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
Date.prototype.toLocale*String() | \npartial (not locale-aware) | \npartial/full (depends on OS) | \npartial (English-only) | \nfull | \n
| WHATWG URL Parser | \npartial (no IDN support) | \nfull | \nfull | \nfull | \n
require('buffer').transcode() | \nnone (function does not exist) | \nfull | \nfull | \nfull | \n
| REPL | \npartial (inaccurate line editing) | \nfull | \nfull | \nfull | \n
require('util').TextDecoder | \npartial (basic encodings support) | \npartial/full (depends on OS) | \npartial (Unicode-only) | \nfull | \n
RegExp Unicode Property Escapes | \nnone (invalid RegExp error) | \nfull | \nfull | \nfull | \n
The \"(not locale-aware)\" designation denotes that the function carries out its\noperation just like the non-Locale version of the function, if one\nexists. For example, under none mode, Date.prototype.toLocaleString()'s\noperation is identical to that of Date.prototype.toString().
If this option is chosen, most internationalization features mentioned above\nwill be unavailable in the resulting node binary.
Node.js can link against an ICU build already installed on the system. In fact,\nmost Linux distributions already come with ICU installed, and this option would\nmake it possible to reuse the same set of data used by other components in the\nOS.
\nFunctionalities that only require the ICU library itself, such as\nString.prototype.normalize() and the WHATWG URL parser, are fully\nsupported under system-icu. Features that require ICU locale data in\naddition, such as Intl.DateTimeFormat may be fully or partially\nsupported, depending on the completeness of the ICU data installed on the\nsystem.
This option makes the resulting binary link against the ICU library statically,\nand includes a subset of ICU data (typically only the English locale) within\nthe node executable.
Functionalities that only require the ICU library itself, such as\nString.prototype.normalize() and the WHATWG URL parser, are fully\nsupported under small-icu. Features that require ICU locale data in addition,\nsuch as Intl.DateTimeFormat, generally only work with the English locale:
const january = new Date(9e8);\nconst english = new Intl.DateTimeFormat('en', { month: 'long' });\nconst spanish = new Intl.DateTimeFormat('es', { month: 'long' });\n\nconsole.log(english.format(january));\n// Prints \"January\"\nconsole.log(spanish.format(january));\n// Prints \"M01\" on small-icu\n// Should print \"enero\"\nThis mode provides a good balance between features and binary size, and it is\nthe default behavior if no --with-intl flag is passed. The official binaries\nare also built in this mode.
If the small-icu option is used, one can still provide additional locale data\nat runtime so that the JS methods would work for all ICU locales. Assuming the\ndata file is stored at /some/directory, it can be made available to ICU\nthrough either:
The NODE_ICU_DATA environment variable:
env NODE_ICU_DATA=/some/directory node\nThe --icu-data-dir CLI parameter:
node --icu-data-dir=/some/directory\n(If both are specified, the --icu-data-dir CLI parameter takes precedence.)
ICU is able to automatically find and load a variety of data formats, but the\ndata must be appropriate for the ICU version, and the file correctly named.\nThe most common name for the data file is icudt6X[bl].dat, where 6X denotes\nthe intended ICU version, and b or l indicates the system's endianness.\nCheck \"ICU Data\" article in the ICU User Guide for other supported formats\nand more details on ICU data in general.
The full-icu npm module can greatly simplify ICU data installation by\ndetecting the ICU version of the running node executable and downloading the\nappropriate data file. After installing the module through npm i full-icu,\nthe data file will be available at ./node_modules/full-icu. This path can be\nthen passed either to NODE_ICU_DATA or --icu-data-dir as shown above to\nenable full Intl support.
This option makes the resulting binary link against ICU statically and include\na full set of ICU data. A binary created this way has no further external\ndependencies and supports all locales, but might be rather large. See\nBUILDING.md on how to compile a binary using this mode.
", "type": "module", "displayName": "Embed the entire ICU (`full-icu`)" } ], "type": "misc", "displayName": "Options for building Node.js" }, { "textRaw": "Detecting internationalization support", "name": "detecting_internationalization_support", "desc": "To verify that ICU is enabled at all (system-icu, small-icu, or\nfull-icu), simply checking the existence of Intl should suffice:
const hasICU = typeof Intl === 'object';\nAlternatively, checking for process.versions.icu, a property defined only\nwhen ICU is enabled, works too:
const hasICU = typeof process.versions.icu === 'string';\nTo check for support for a non-English locale (i.e. full-icu or\nsystem-icu), Intl.DateTimeFormat can be a good distinguishing factor:
const hasFullICU = (() => {\n try {\n const january = new Date(9e8);\n const spanish = new Intl.DateTimeFormat('es', { month: 'long' });\n return spanish.format(january) === 'enero';\n } catch (err) {\n return false;\n }\n})();\nFor more verbose tests for Intl support, the following resources may be found\nto be helpful:
Intl support is\nbuilt correctly.The assert module provides a simple set of assertion tests that can be used to\ntest invariants.
A strict and a legacy mode exist, while it is recommended to only use\nstrict mode.
For more information about the used equality comparisons see\nMDN's guide on equality comparisons and sameness.
", "classes": [ { "textRaw": "Class: assert.AssertionError", "type": "class", "name": "assert.AssertionError", "desc": "A subclass of Error that indicates the failure of an assertion. All errors\nthrown by the assert module will be instances of the AssertionError class.
A subclass of Error that indicates the failure of an assertion.
All instances contain the built-in Error properties (message and name)\nand:
actual <any> Set to the actual value in case e.g.,\nassert.strictEqual() is used.expected <any> Set to the expected value in case e.g.,\nassert.strictEqual() is used.generatedMessage <boolean> Indicates if the message was auto-generated\n(true) or not.code <string> This is always set to the string ERR_ASSERTION to indicate\nthat the error is actually an assertion error.operator <string> Set to the passed in operator value.const assert = require('assert');\n\n// Generate an AssertionError to compare the error message later:\nconst { message } = new assert.AssertionError({\n actual: 1,\n expected: 2,\n operator: 'strictEqual'\n});\n\n// Verify error output:\ntry {\n assert.strictEqual(1, 2);\n} catch (err) {\n assert(err instanceof assert.AssertionError);\n assert.strictEqual(err.message, message);\n assert.strictEqual(err.name, 'AssertionError [ERR_ASSERTION]');\n assert.strictEqual(err.actual, 1);\n assert.strictEqual(err.expected, 2);\n assert.strictEqual(err.code, 'ERR_ASSERTION');\n assert.strictEqual(err.operator, 'strictEqual');\n assert.strictEqual(err.generatedMessage, true);\n}\nWhen using the strict mode, any assert function will use the equality used\nin the strict function mode. So assert.deepEqual() will, for example,\nwork the same as assert.deepStrictEqual().
On top of that, error messages which involve objects produce an error diff\ninstead of displaying both objects. That is not the case for the legacy mode.
\nIt can be accessed using:
\nconst assert = require('assert').strict;\nExample error diff:
\nconst assert = require('assert').strict;\n\nassert.deepEqual([[[1, 2, 3]], 4, 5], [[[1, 2, '3']], 4, 5]);\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual ... Lines skipped\n//\n// [\n// [\n// ...\n// 2,\n// - 3\n// + '3'\n// ],\n// ...\n// 5\n// ]\nTo deactivate the colors, use the NODE_DISABLE_COLORS environment variable.\nPlease note that this will also deactivate the colors in the REPL.
When accessing assert directly instead of using the strict property, the\nAbstract Equality Comparison will be used for any function without \"strict\"\nin its name, such as assert.deepEqual().
It can be accessed using:
\nconst assert = require('assert');\nIt is recommended to use the strict mode instead as the\nAbstract Equality Comparison can often have surprising results. This is\nespecially true for assert.deepEqual(), where the comparison rules are\nlax:
// WARNING: This does not throw an AssertionError!\nassert.deepEqual(/a/gi, new Date());\nAn alias of assert.ok().
Strict mode
\nAn alias of assert.deepStrictEqual().
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.deepStrictEqual()instead.
Tests for deep equality between the actual and expected parameters.\nPrimitive values are compared with the Abstract Equality Comparison\n( == ).
Only enumerable \"own\" properties are considered. The\nassert.deepEqual() implementation does not test the\n[[Prototype]] of objects or enumerable own Symbol\nproperties. For such checks, consider using assert.deepStrictEqual()\ninstead. assert.deepEqual() can have potentially surprising results. The\nfollowing example does not throw an AssertionError because the properties on\nthe RegExp object are not enumerable:
// WARNING: This does not throw an AssertionError!\nassert.deepEqual(/a/gi, new Date());\nAn exception is made for Map and Set. Maps and Sets have their\ncontained items compared too, as expected.
\"Deep\" equality means that the enumerable \"own\" properties of child objects\nare evaluated also:
\nconst assert = require('assert');\n\nconst obj1 = {\n a: {\n b: 1\n }\n};\nconst obj2 = {\n a: {\n b: 2\n }\n};\nconst obj3 = {\n a: {\n b: 1\n }\n};\nconst obj4 = Object.create(obj1);\n\nassert.deepEqual(obj1, obj1);\n// OK\n\n// Values of b are different:\nassert.deepEqual(obj1, obj2);\n// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }\n\nassert.deepEqual(obj1, obj3);\n// OK\n\n// Prototypes are ignored:\nassert.deepEqual(obj1, obj4);\n// AssertionError: { a: { b: 1 } } deepEqual {}\nIf the values are not equal, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.
Tests for deep equality between the actual and expected parameters.\n\"Deep\" equality means that the enumerable \"own\" properties of child objects\nare recursively evaluated also by the following rules.
Object.is().[[Prototype]] of objects are compared using\nthe Strict Equality Comparison.Error names and messages are always compared, even if these are not\nenumerable properties.Symbol properties are compared as well.Object properties are compared unordered.Map keys and Set items are compared unordered.WeakMap and WeakSet comparison does not rely on their values. See\nbelow for further details.const assert = require('assert').strict;\n\n// This fails because 1 !== '1'.\nassert.deepStrictEqual({ a: 1 }, { a: '1' });\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// {\n// - a: 1\n// + a: '1'\n// }\n\n// The following objects don't have own properties\nconst date = new Date();\nconst object = {};\nconst fakeDate = {};\nObject.setPrototypeOf(fakeDate, Date.prototype);\n\n// Different [[Prototype]]:\nassert.deepStrictEqual(object, fakeDate);\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// - {}\n// + Date {}\n\n// Different type tags:\nassert.deepStrictEqual(date, fakeDate);\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// - 2018-04-26T00:49:08.604Z\n// + Date {}\n\nassert.deepStrictEqual(NaN, NaN);\n// OK, because of the SameValue comparison\n\n// Different unwrapped numbers:\nassert.deepStrictEqual(new Number(1), new Number(2));\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// - [Number: 1]\n// + [Number: 2]\n\nassert.deepStrictEqual(new String('foo'), Object('foo'));\n// OK because the object and the string are identical when unwrapped.\n\nassert.deepStrictEqual(-0, -0);\n// OK\n\n// Different zeros using the SameValue Comparison:\nassert.deepStrictEqual(0, -0);\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// - 0\n// + -0\n\nconst symbol1 = Symbol();\nconst symbol2 = Symbol();\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol1]: 1 });\n// OK, because it is the same symbol on both objects.\nassert.deepStrictEqual({ [symbol1]: 1 }, { [symbol2]: 1 });\n// AssertionError [ERR_ASSERTION]: Input objects not identical:\n// {\n// [Symbol()]: 1\n// }\n\nconst weakMap1 = new WeakMap();\nconst weakMap2 = new WeakMap([[{}, {}]]);\nconst weakMap3 = new WeakMap();\nweakMap3.unequal = true;\n\nassert.deepStrictEqual(weakMap1, weakMap2);\n// OK, because it is impossible to compare the entries\n\n// Fails because weakMap3 has a property that weakMap1 does not contain:\nassert.deepStrictEqual(weakMap1, weakMap3);\n// AssertionError: Input A expected to strictly deep-equal input B:\n// + expected - actual\n// WeakMap {\n// - [items unknown]\n// + [items unknown],\n// + unequal: true\n// }\nIf the values are not equal, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.
Awaits the asyncFn promise or, if asyncFn is a function, immediately\ncalls the function and awaits the returned promise to complete. It will then\ncheck that the promise is not rejected.
If asyncFn is a function and it throws an error synchronously,\nassert.doesNotReject() will return a rejected Promise with that error. If\nthe function does not return a promise, assert.doesNotReject() will return a\nrejected Promise with an ERR_INVALID_RETURN_VALUE error. In both cases\nthe error handler is skipped.
Using assert.doesNotReject() is actually not useful because there is little\nbenefit in catching a rejection and then rejecting it again. Instead, consider\nadding a comment next to the specific code path that should not reject and keep\nerror messages as expressive as possible.
If specified, error can be a Class, RegExp or a validation\nfunction. See assert.throws() for more details.
Besides the async nature to await the completion behaves identically to\nassert.doesNotThrow().
(async () => {\n await assert.doesNotReject(\n async () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError\n );\n})();\nassert.doesNotReject(Promise.reject(new TypeError('Wrong value')))\n .then(() => {\n // ...\n });\nAsserts that the function fn does not throw an error.
Using assert.doesNotThrow() is actually not useful because there\nis no benefit in catching an error and then rethrowing it. Instead, consider\nadding a comment next to the specific code path that should not throw and keep\nerror messages as expressive as possible.
When assert.doesNotThrow() is called, it will immediately call the fn\nfunction.
If an error is thrown and it is the same type as that specified by the error\nparameter, then an AssertionError is thrown. If the error is of a different\ntype, or if the error parameter is undefined, the error is propagated back\nto the caller.
If specified, error can be a Class, RegExp or a validation\nfunction. See assert.throws() for more details.
The following, for instance, will throw the TypeError because there is no\nmatching error type in the assertion:
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError\n);\nHowever, the following will result in an AssertionError with the message\n'Got unwanted exception...':
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n TypeError\n);\nIf an AssertionError is thrown and a value is provided for the message\nparameter, the value of message will be appended to the AssertionError\nmessage:
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n /Wrong value/,\n 'Whoops'\n);\n// Throws: AssertionError: Got unwanted exception: Whoops\nStrict mode
\nAn alias of assert.strictEqual().
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.strictEqual()instead.
Tests shallow, coercive equality between the actual and expected parameters\nusing the Abstract Equality Comparison ( == ).
const assert = require('assert');\n\nassert.equal(1, 1);\n// OK, 1 == 1\nassert.equal(1, '1');\n// OK, 1 == '1'\n\nassert.equal(1, 2);\n// AssertionError: 1 == 2\nassert.equal({ a: { b: 1 } }, { a: { b: 1 } });\n// AssertionError: { a: { b: 1 } } == { a: { b: 1 } }\nIf the values are not equal, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.
Throws an AssertionError with the provided error message or a default error\nmessage. If the message parameter is an instance of an Error then it\nwill be thrown instead of the AssertionError.
const assert = require('assert').strict;\n\nassert.fail();\n// AssertionError [ERR_ASSERTION]: Failed\n\nassert.fail('boom');\n// AssertionError [ERR_ASSERTION]: boom\n\nassert.fail(new TypeError('need array'));\n// TypeError: need array\nUsing assert.fail() with more than two arguments is possible but deprecated.\nSee below for further details.
If message is falsy, the error message is set as the values of actual and\nexpected separated by the provided operator. If just the two actual and\nexpected arguments are provided, operator will default to '!='. If\nmessage is provided as third argument it will be used as the error message and\nthe other arguments will be stored as properties on the thrown object. If\nstackStartFn is provided, all stack frames above that function will be\nremoved from stacktrace (see Error.captureStackTrace). If no arguments are\ngiven, the default message Failed will be used.
const assert = require('assert').strict;\n\nassert.fail('a', 'b');\n// AssertionError [ERR_ASSERTION]: 'a' != 'b'\n\nassert.fail(1, 2, undefined, '>');\n// AssertionError [ERR_ASSERTION]: 1 > 2\n\nassert.fail(1, 2, 'fail');\n// AssertionError [ERR_ASSERTION]: fail\n\nassert.fail(1, 2, 'whoops', '>');\n// AssertionError [ERR_ASSERTION]: whoops\n\nassert.fail(1, 2, new TypeError('need array'));\n// TypeError: need array\nIn the last three cases actual, expected, and operator have no\ninfluence on the error message.
Example use of stackStartFn for truncating the exception's stacktrace:
function suppressFrame() {\n assert.fail('a', 'b', undefined, '!==', suppressFrame);\n}\nsuppressFrame();\n// AssertionError [ERR_ASSERTION]: 'a' !== 'b'\n// at repl:1:1\n// at ContextifyScript.Script.runInThisContext (vm.js:44:33)\n// ...\nThrows value if value is not undefined or null. This is useful when\ntesting the error argument in callbacks. The stack trace contains all frames\nfrom the error passed to ifError() including the potential new frames for\nifError() itself.
const assert = require('assert').strict;\n\nassert.ifError(null);\n// OK\nassert.ifError(0);\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0\nassert.ifError('error');\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'\nassert.ifError(new Error());\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error\n\n// Create some random error frames.\nlet err;\n(function errorFrame() {\n err = new Error('test error');\n})();\n\n(function ifErrorFrame() {\n assert.ifError(err);\n})();\n// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error\n// at ifErrorFrame\n// at errorFrame\nStrict mode
\nAn alias of assert.notDeepStrictEqual().
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.notDeepStrictEqual()instead.
Tests for any deep inequality. Opposite of assert.deepEqual().
const assert = require('assert');\n\nconst obj1 = {\n a: {\n b: 1\n }\n};\nconst obj2 = {\n a: {\n b: 2\n }\n};\nconst obj3 = {\n a: {\n b: 1\n }\n};\nconst obj4 = Object.create(obj1);\n\nassert.notDeepEqual(obj1, obj1);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj2);\n// OK\n\nassert.notDeepEqual(obj1, obj3);\n// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj4);\n// OK\nIf the values are deeply equal, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.
Tests for deep strict inequality. Opposite of assert.deepStrictEqual().
const assert = require('assert').strict;\n\nassert.notDeepStrictEqual({ a: 1 }, { a: '1' });\n// OK\nIf the values are deeply and strictly equal, an AssertionError is thrown with\na message property set equal to the value of the message parameter. If the\nmessage parameter is undefined, a default error message is assigned. If the\nmessage parameter is an instance of an Error then it will be thrown\ninstead of the AssertionError.
Strict mode
\nAn alias of assert.notStrictEqual().
Legacy mode
\n\n\nStability: 0 - Deprecated: Use
\nassert.notStrictEqual()instead.
Tests shallow, coercive inequality with the Abstract Equality Comparison\n( != ).
const assert = require('assert');\n\nassert.notEqual(1, 2);\n// OK\n\nassert.notEqual(1, 1);\n// AssertionError: 1 != 1\n\nassert.notEqual(1, '1');\n// AssertionError: 1 != '1'\nIf the values are equal, an AssertionError is thrown with a message property\nset equal to the value of the message parameter. If the message parameter is\nundefined, a default error message is assigned. If the message parameter is an\ninstance of an Error then it will be thrown instead of the\nAssertionError.
Tests strict inequality between the actual and expected parameters as\ndetermined by the SameValue Comparison.
const assert = require('assert').strict;\n\nassert.notStrictEqual(1, 2);\n// OK\n\nassert.notStrictEqual(1, 1);\n// AssertionError [ERR_ASSERTION]: Identical input passed to notStrictEqual: 1\n\nassert.notStrictEqual(1, '1');\n// OK\nIf the values are strictly equal, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.
Tests if value is truthy. It is equivalent to\nassert.equal(!!value, true, message).
If value is not truthy, an AssertionError is thrown with a message\nproperty set equal to the value of the message parameter. If the message\nparameter is undefined, a default error message is assigned. If the message\nparameter is an instance of an Error then it will be thrown instead of the\nAssertionError.\nIf no arguments are passed in at all message will be set to the string:\n'No value argument passed to `assert.ok()`'.
Be aware that in the repl the error message will be different to the one\nthrown in a file! See below for further details.
const assert = require('assert').strict;\n\nassert.ok(true);\n// OK\nassert.ok(1);\n// OK\n\nassert.ok();\n// AssertionError: No value argument passed to `assert.ok()`\n\nassert.ok(false, 'it\\'s false');\n// AssertionError: it's false\n\n// In the repl:\nassert.ok(typeof 123 === 'string');\n// AssertionError: false == true\n\n// In a file (e.g. test.js):\nassert.ok(typeof 123 === 'string');\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(typeof 123 === 'string')\n\nassert.ok(false);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(false)\n\nassert.ok(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert.ok(0)\n\n// Using `assert()` works the same:\nassert(0);\n// AssertionError: The expression evaluated to a falsy value:\n//\n// assert(0)\nAwaits the asyncFn promise or, if asyncFn is a function, immediately\ncalls the function and awaits the returned promise to complete. It will then\ncheck that the promise is rejected.
If asyncFn is a function and it throws an error synchronously,\nassert.rejects() will return a rejected Promise with that error. If the\nfunction does not return a promise, assert.rejects() will return a rejected\nPromise with an ERR_INVALID_RETURN_VALUE error. In both cases the error\nhandler is skipped.
Besides the async nature to await the completion behaves identically to\nassert.throws().
If specified, error can be a Class, RegExp, a validation function,\nan object where each property will be tested for, or an instance of error where\neach property will be tested for including the non-enumerable message and\nname properties.
If specified, message will be the message provided by the AssertionError if\nthe asyncFn fails to reject.
(async () => {\n await assert.rejects(\n async () => {\n throw new TypeError('Wrong value');\n },\n {\n name: 'TypeError',\n message: 'Wrong value'\n }\n );\n})();\nassert.rejects(\n Promise.reject(new Error('Wrong value')),\n Error\n).then(() => {\n // ...\n});\nNote that error cannot be a string. If a string is provided as the second\nargument, then error is assumed to be omitted and the string will be used for\nmessage instead. This can lead to easy-to-miss mistakes. Please read the\nexample in assert.throws() carefully if using a string as the second\nargument gets considered.
Tests strict equality between the actual and expected parameters as\ndetermined by the SameValue Comparison.
const assert = require('assert').strict;\n\nassert.strictEqual(1, 2);\n// AssertionError [ERR_ASSERTION]: Input A expected to strictly equal input B:\n// + expected - actual\n// - 1\n// + 2\n\nassert.strictEqual(1, 1);\n// OK\n\nassert.strictEqual(1, '1');\n// AssertionError [ERR_ASSERTION]: Input A expected to strictly equal input B:\n// + expected - actual\n// - 1\n// + '1'\nIf the values are not strictly equal, an AssertionError is thrown with a\nmessage property set equal to the value of the message parameter. If the\nmessage parameter is undefined, a default error message is assigned. If the\nmessage parameter is an instance of an Error then it will be thrown\ninstead of the AssertionError.
Expects the function fn to throw an error.
If specified, error can be a Class, RegExp, a validation function,\na validation object where each property will be tested for strict deep equality,\nor an instance of error where each property will be tested for strict deep\nequality including the non-enumerable message and name properties. When\nusing an object, it is also possible to use a regular expression, when\nvalidating against a string property. See below for examples.
If specified, message will be appended to the message provided by the\nAssertionError if the fn call fails to throw or in case the error validation\nfails.
Custom validation object/error instance:
\nconst err = new TypeError('Wrong value');\nerr.code = 404;\nerr.foo = 'bar';\nerr.info = {\n nested: true,\n baz: 'text'\n};\nerr.reg = /abc/i;\n\nassert.throws(\n () => {\n throw err;\n },\n {\n name: 'TypeError',\n message: 'Wrong value',\n info: {\n nested: true,\n baz: 'text'\n }\n // Note that only properties on the validation object will be tested for.\n // Using nested objects requires all properties to be present. Otherwise\n // the validation is going to fail.\n }\n);\n\n// Using regular expressions to validate error properties:\nassert.throws(\n () => {\n throw err;\n },\n {\n // The `name` and `message` properties are strings and using regular\n // expressions on those will match against the string. If they fail, an\n // error is thrown.\n name: /^TypeError$/,\n message: /Wrong/,\n foo: 'bar',\n info: {\n nested: true,\n // It is not possible to use regular expressions for nested properties!\n baz: 'text'\n },\n // The `reg` property contains a regular expression and only if the\n // validation object contains an identical regular expression, it is going\n // to pass.\n reg: /abc/i\n }\n);\n\n// Fails due to the different `message` and `name` properties:\nassert.throws(\n () => {\n const otherErr = new Error('Not found');\n otherErr.code = 404;\n throw otherErr;\n },\n err // This tests for `message`, `name` and `code`.\n);\nValidate instanceof using constructor:
\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n Error\n);\nValidate error message using RegExp:
Using a regular expression runs .toString on the error object, and will\ntherefore also include the error name.
assert.throws(\n () => {\n throw new Error('Wrong value');\n },\n /^Error: Wrong value$/\n);\nCustom error validation:
\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n function(err) {\n if ((err instanceof Error) && /value/.test(err)) {\n return true;\n }\n },\n 'unexpected error'\n);\nNote that error cannot be a string. If a string is provided as the second\nargument, then error is assumed to be omitted and the string will be used for\nmessage instead. This can lead to easy-to-miss mistakes. Using the same\nmessage as the thrown error message is going to result in an\nERR_AMBIGUOUS_ARGUMENT error. Please read the example below carefully if using\na string as the second argument gets considered:
function throwingFirst() {\n throw new Error('First');\n}\nfunction throwingSecond() {\n throw new Error('Second');\n}\nfunction notThrowing() {}\n\n// The second argument is a string and the input function threw an Error.\n// The first case will not throw as it does not match for the error message\n// thrown by the input function!\nassert.throws(throwingFirst, 'Second');\n// In the next example the message has no benefit over the message from the\n// error and since it is not clear if the user intended to actually match\n// against the error message, Node.js thrown an `ERR_AMBIGUOUS_ARGUMENT` error.\nassert.throws(throwingSecond, 'Second');\n// Throws an error:\n// TypeError [ERR_AMBIGUOUS_ARGUMENT]\n\n// The string is only used (as message) in case the function does not throw:\nassert.throws(notThrowing, 'Second');\n// AssertionError [ERR_ASSERTION]: Missing expected exception: Second\n\n// If it was intended to match for the error message do this instead:\nassert.throws(throwingSecond, /Second$/);\n// Does not throw because the error messages match.\nassert.throws(throwingFirst, /Second$/);\n// Throws an error:\n// Error: First\n// at throwingFirst (repl:2:9)\nDue to the confusing notation, it is recommended not to use a string as the\nsecond argument. This might lead to difficult-to-spot errors.
" } ], "type": "module", "displayName": "Assert" }, { "textRaw": "Async Hooks", "name": "async_hooks", "introduced_in": "v8.1.0", "stability": 1, "stabilityText": "Experimental", "desc": "The async_hooks module provides an API to register callbacks tracking the\nlifetime of asynchronous resources created inside a Node.js application.\nIt can be accessed using:
const async_hooks = require('async_hooks');\nAn asynchronous resource represents an object with an associated callback.\nThis callback may be called multiple times, for example, the 'connection'\nevent in net.createServer(), or just a single time like in fs.open().\nA resource can also be closed before the callback is called. AsyncHook does\nnot explicitly distinguish between these different cases but will represent them\nas the abstract concept that is a resource.
If Workers are used, each thread has an independent async_hooks\ninterface, and each thread will use a new set of async IDs.
Following is a simple overview of the public API.
\nconst async_hooks = require('async_hooks');\n\n// Return the ID of the current execution context.\nconst eid = async_hooks.executionAsyncId();\n\n// Return the ID of the handle responsible for triggering the callback of the\n// current execution scope to call.\nconst tid = async_hooks.triggerAsyncId();\n\n// Create a new AsyncHook instance. All of these callbacks are optional.\nconst asyncHook =\n async_hooks.createHook({ init, before, after, destroy, promiseResolve });\n\n// Allow callbacks of this AsyncHook instance to call. This is not an implicit\n// action after running the constructor, and must be explicitly run to begin\n// executing callbacks.\nasyncHook.enable();\n\n// Disable listening for new asynchronous events.\nasyncHook.disable();\n\n//\n// The following are the callbacks that can be passed to createHook().\n//\n\n// init is called during object construction. The resource may not have\n// completed construction when this callback runs, therefore all fields of the\n// resource referenced by \"asyncId\" may not have been populated.\nfunction init(asyncId, type, triggerAsyncId, resource) { }\n\n// before is called just before the resource's callback is called. It can be\n// called 0-N times for handles (e.g. TCPWrap), and will be called exactly 1\n// time for requests (e.g. FSReqWrap).\nfunction before(asyncId) { }\n\n// after is called just after the resource's callback has finished.\nfunction after(asyncId) { }\n\n// destroy is called when an AsyncWrap instance is destroyed.\nfunction destroy(asyncId) { }\n\n// promiseResolve is called only for promise resources, when the\n// `resolve` function passed to the `Promise` constructor is invoked\n// (either directly or through other means of resolving a promise).\nfunction promiseResolve(asyncId) { }\nRegisters functions to be called for different lifetime events of each async\noperation.
\nThe callbacks init()/before()/after()/destroy() are called for the\nrespective asynchronous event during a resource's lifetime.
All callbacks are optional. For example, if only resource cleanup needs to\nbe tracked, then only the destroy callback needs to be passed. The\nspecifics of all functions that can be passed to callbacks is in the\nHook Callbacks section.
const async_hooks = require('async_hooks');\n\nconst asyncHook = async_hooks.createHook({\n init(asyncId, type, triggerAsyncId, resource) { },\n destroy(asyncId) { }\n});\nNote that the callbacks will be inherited via the prototype chain:
\nclass MyAsyncCallbacks {\n init(asyncId, type, triggerAsyncId, resource) { }\n destroy(asyncId) {}\n}\n\nclass MyAddedCallbacks extends MyAsyncCallbacks {\n before(asyncId) { }\n after(asyncId) { }\n}\n\nconst asyncHook = async_hooks.createHook(new MyAddedCallbacks());\nIf any AsyncHook callbacks throw, the application will print the stack trace\nand exit. The exit path does follow that of an uncaught exception, but\nall 'uncaughtException' listeners are removed, thus forcing the process to\nexit. The 'exit' callbacks will still be called unless the application is run\nwith --abort-on-uncaught-exception, in which case a stack trace will be\nprinted and the application exits, leaving a core file.
The reason for this error handling behavior is that these callbacks are running\nat potentially volatile points in an object's lifetime, for example during\nclass construction and destruction. Because of this, it is deemed necessary to\nbring down the process quickly in order to prevent an unintentional abort in the\nfuture. This is subject to change in the future if a comprehensive analysis is\nperformed to ensure an exception can follow the normal control flow without\nunintentional side effects.
", "type": "module", "displayName": "Error Handling" }, { "textRaw": "Printing in AsyncHooks callbacks", "name": "printing_in_asynchooks_callbacks", "desc": "Because printing to the console is an asynchronous operation, console.log()\nwill cause the AsyncHooks callbacks to be called. Using console.log() or\nsimilar asynchronous operations inside an AsyncHooks callback function will thus\ncause an infinite recursion. An easy solution to this when debugging is to use a\nsynchronous logging operation such as fs.writeFileSync(file, msg, flag).\nThis will print to the file and will not invoke AsyncHooks recursively because\nit is synchronous.
const fs = require('fs');\nconst util = require('util');\n\nfunction debug(...args) {\n // use a function like this one when debugging inside an AsyncHooks callback\n fs.writeFileSync('log.out', `${util.format(...args)}\\n`, { flag: 'a' });\n}\nIf an asynchronous operation is needed for logging, it is possible to keep\ntrack of what caused the asynchronous operation using the information\nprovided by AsyncHooks itself. The logging should then be skipped when\nit was the logging itself that caused AsyncHooks callback to call. By\ndoing this the otherwise infinite recursion is broken.
", "type": "module", "displayName": "Printing in AsyncHooks callbacks" } ] }, { "textRaw": "asyncHook.enable()", "type": "method", "name": "enable", "signatures": [ { "return": { "textRaw": "Returns: {AsyncHook} A reference to `asyncHook`.", "name": "return", "type": "AsyncHook", "desc": "A reference to `asyncHook`." }, "params": [] } ], "desc": "Enable the callbacks for a given AsyncHook instance. If no callbacks are\nprovided enabling is a noop.
The AsyncHook instance is disabled by default. If the AsyncHook instance\nshould be enabled immediately after creation, the following pattern can be used.
const async_hooks = require('async_hooks');\n\nconst hook = async_hooks.createHook(callbacks).enable();\nDisable the callbacks for a given AsyncHook instance from the global pool of\nAsyncHook callbacks to be executed. Once a hook has been disabled it will not\nbe called again until enabled.
For API consistency disable() also returns the AsyncHook instance.
const async_hooks = require('async_hooks');\n\nconsole.log(async_hooks.executionAsyncId()); // 1 - bootstrap\nfs.open(path, 'r', (err, fd) => {\n console.log(async_hooks.executionAsyncId()); // 6 - open()\n});\nThe ID returned from executionAsyncId() is related to execution timing, not\ncausality (which is covered by triggerAsyncId()):
const server = net.createServer((conn) => {\n // Returns the ID of the server, not of the new connection, because the\n // callback runs in the execution scope of the server's MakeCallback().\n async_hooks.executionAsyncId();\n\n}).listen(port, () => {\n // Returns the ID of a TickObject (i.e. process.nextTick()) because all\n // callbacks passed to .listen() are wrapped in a nextTick().\n async_hooks.executionAsyncId();\n});\nNote that promise contexts may not get precise executionAsyncIds by default.\nSee the section on promise execution tracking.
const server = net.createServer((conn) => {\n // The resource that caused (or triggered) this callback to be called\n // was that of the new connection. Thus the return value of triggerAsyncId()\n // is the asyncId of \"conn\".\n async_hooks.triggerAsyncId();\n\n}).listen(port, () => {\n // Even though all callbacks passed to .listen() are wrapped in a nextTick()\n // the callback itself exists because the call to the server's .listen()\n // was made. So the return value would be the ID of the server.\n async_hooks.triggerAsyncId();\n});\nNote that promise contexts may not get valid triggerAsyncIds by default. See\nthe section on promise execution tracking.
Key events in the lifetime of asynchronous events have been categorized into\nfour areas: instantiation, before/after the callback is called, and when the\ninstance is destroyed.
", "methods": [ { "textRaw": "init(asyncId, type, triggerAsyncId, resource)", "type": "method", "name": "init", "signatures": [ { "params": [ { "textRaw": "`asyncId` {number} A unique ID for the async resource.", "name": "asyncId", "type": "number", "desc": "A unique ID for the async resource." }, { "textRaw": "`type` {string} The type of the async resource.", "name": "type", "type": "string", "desc": "The type of the async resource." }, { "textRaw": "`triggerAsyncId` {number} The unique ID of the async resource in whose execution context this async resource was created.", "name": "triggerAsyncId", "type": "number", "desc": "The unique ID of the async resource in whose execution context this async resource was created." }, { "textRaw": "`resource` {Object} Reference to the resource representing the async operation, needs to be released during _destroy_.", "name": "resource", "type": "Object", "desc": "Reference to the resource representing the async operation, needs to be released during _destroy_." } ] } ], "desc": "Called when a class is constructed that has the possibility to emit an\nasynchronous event. This does not mean the instance must call\nbefore/after before destroy is called, only that the possibility\nexists.
This behavior can be observed by doing something like opening a resource then\nclosing it before the resource can be used. The following snippet demonstrates\nthis.
\nrequire('net').createServer().listen(function() { this.close(); });\n// OR\nclearTimeout(setTimeout(() => {}, 10));\nEvery new resource is assigned an ID that is unique within the scope of the\ncurrent Node.js instance.
", "modules": [ { "textRaw": "`type`", "name": "`type`", "desc": "The type is a string identifying the type of resource that caused\ninit to be called. Generally, it will correspond to the name of the\nresource's constructor.
FSEVENTWRAP, FSREQWRAP, GETADDRINFOREQWRAP, GETNAMEINFOREQWRAP, HTTPPARSER,\nJSSTREAM, PIPECONNECTWRAP, PIPEWRAP, PROCESSWRAP, QUERYWRAP, SHUTDOWNWRAP,\nSIGNALWRAP, STATWATCHER, TCPCONNECTWRAP, TCPSERVERWRAP, TCPWRAP, TIMERWRAP,\nTTYWRAP, UDPSENDWRAP, UDPWRAP, WRITEWRAP, ZLIB, SSLCONNECTION, PBKDF2REQUEST,\nRANDOMBYTESREQUEST, TLSWRAP, Timeout, Immediate, TickObject\nThere is also the PROMISE resource type, which is used to track Promise\ninstances and asynchronous work scheduled by them.
Users are able to define their own type when using the public embedder API.
It is possible to have type name collisions. Embedders are encouraged to use\nunique prefixes, such as the npm package name, to prevent collisions when\nlistening to the hooks.
", "type": "module", "displayName": "`type`" }, { "textRaw": "`triggerAsyncId`", "name": "`triggerasyncid`", "desc": "triggerAsyncId is the asyncId of the resource that caused (or \"triggered\")\nthe new resource to initialize and that caused init to call. This is different\nfrom async_hooks.executionAsyncId() that only shows when a resource was\ncreated, while triggerAsyncId shows why a resource was created.
The following is a simple demonstration of triggerAsyncId:
async_hooks.createHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = async_hooks.executionAsyncId();\n fs.writeSync(\n 1, `${type}(${asyncId}): trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n }\n}).enable();\n\nrequire('net').createServer((conn) => {}).listen(8080);\nOutput when hitting the server with nc localhost 8080:
TCPSERVERWRAP(5): trigger: 1 execution: 1\nTCPWRAP(7): trigger: 5 execution: 0\nThe TCPSERVERWRAP is the server which receives the connections.
The TCPWRAP is the new connection from the client. When a new\nconnection is made, the TCPWrap instance is immediately constructed. This\nhappens outside of any JavaScript stack. (An executionAsyncId() of 0 means\nthat it is being executed from C++ with no JavaScript stack above it.) With only\nthat information, it would be impossible to link resources together in\nterms of what caused them to be created, so triggerAsyncId is given the task\nof propagating what resource is responsible for the new resource's existence.
resource is an object that represents the actual async resource that has\nbeen initialized. This can contain useful information that can vary based on\nthe value of type. For instance, for the GETADDRINFOREQWRAP resource type,\nresource provides the hostname used when looking up the IP address for the\nhost in net.Server.listen(). The API for accessing this information is\ncurrently not considered public, but using the Embedder API, users can provide\nand document their own resource objects. For example, such a resource object\ncould contain the SQL query being executed.
In the case of Promises, the resource object will have promise property\nthat refers to the Promise that is being initialized, and an\nisChainedPromise property, set to true if the promise has a parent promise,\nand false otherwise. For example, in the case of b = a.then(handler), a is\nconsidered a parent Promise of b. Here, b is considered a chained promise.
In some cases the resource object is reused for performance reasons, it is\nthus not safe to use it as a key in a WeakMap or add properties to it.
The following is an example with additional information about the calls to\ninit between the before and after calls, specifically what the\ncallback to listen() will look like. The output formatting is slightly more\nelaborate to make calling context easier to see.
let indent = 0;\nasync_hooks.createHook({\n init(asyncId, type, triggerAsyncId) {\n const eid = async_hooks.executionAsyncId();\n const indentStr = ' '.repeat(indent);\n fs.writeSync(\n 1,\n `${indentStr}${type}(${asyncId}):` +\n ` trigger: ${triggerAsyncId} execution: ${eid}\\n`);\n },\n before(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}before: ${asyncId}\\n`, { flag: 'a' });\n indent += 2;\n },\n after(asyncId) {\n indent -= 2;\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}after: ${asyncId}\\n`, { flag: 'a' });\n },\n destroy(asyncId) {\n const indentStr = ' '.repeat(indent);\n fs.writeFileSync('log.out',\n `${indentStr}destroy: ${asyncId}\\n`, { flag: 'a' });\n },\n}).enable();\n\nrequire('net').createServer(() => {}).listen(8080, () => {\n // Let's wait 10ms before logging the server started.\n setTimeout(() => {\n console.log('>>>', async_hooks.executionAsyncId());\n }, 10);\n});\nOutput from only starting the server:
\nTCPSERVERWRAP(5): trigger: 1 execution: 1\nTickObject(6): trigger: 5 execution: 1\nbefore: 6\n Timeout(7): trigger: 6 execution: 6\nafter: 6\ndestroy: 6\nbefore: 7\n>>> 7\n TickObject(8): trigger: 7 execution: 7\nafter: 7\nbefore: 8\nafter: 8\nAs illustrated in the example, executionAsyncId() and execution each specify\nthe value of the current execution context; which is delineated by calls to\nbefore and after.
Only using execution to graph resource allocation results in the following:
Timeout(7) -> TickObject(6) -> root(1)\nThe TCPSERVERWRAP is not part of this graph, even though it was the reason for\nconsole.log() being called. This is because binding to a port without a\nhostname is a synchronous operation, but to maintain a completely asynchronous\nAPI the user's callback is placed in a process.nextTick().
The graph only shows when a resource was created, not why, so to track\nthe why use triggerAsyncId.
When an asynchronous operation is initiated (such as a TCP server receiving a\nnew connection) or completes (such as writing data to disk) a callback is\ncalled to notify the user. The before callback is called just before said\ncallback is executed. asyncId is the unique identifier assigned to the\nresource about to execute the callback.
The before callback will be called 0 to N times. The before callback\nwill typically be called 0 times if the asynchronous operation was cancelled\nor, for example, if no connections are received by a TCP server. Persistent\nasynchronous resources like a TCP server will typically call the before\ncallback multiple times, while other operations like fs.open() will call\nit only once.
Called immediately after the callback specified in before is completed.
If an uncaught exception occurs during execution of the callback, then after\nwill run after the 'uncaughtException' event is emitted or a domain's\nhandler runs.
Called after the resource corresponding to asyncId is destroyed. It is also\ncalled asynchronously from the embedder API emitDestroy().
Some resources depend on garbage collection for cleanup, so if a reference is\nmade to the resource object passed to init it is possible that destroy\nwill never be called, causing a memory leak in the application. If the resource\ndoes not depend on garbage collection, then this will not be an issue.
Called when the resolve function passed to the Promise constructor is\ninvoked (either directly or through other means of resolving a promise).
Note that resolve() does not do any observable synchronous work.
The Promise is not necessarily fulfilled or rejected at this point if the\nPromise was resolved by assuming the state of another Promise.
new Promise((resolve) => resolve(true)).then((a) => {});\ncalls the following callbacks:
\ninit for PROMISE with id 5, trigger id: 1\n promise resolve 5 # corresponds to resolve(true)\ninit for PROMISE with id 6, trigger id: 5 # the Promise returned by then()\n before 6 # the then() callback is entered\n promise resolve 6 # the then() callback resolves the promise by returning\n after 6\nBy default, promise executions are not assigned asyncIds due to the relatively\nexpensive nature of the promise introspection API provided by\nV8. This means that programs using promises or async/await will not get\ncorrect execution and trigger ids for promise callback contexts by default.
const ah = require('async_hooks');\nPromise.resolve(1729).then(() => {\n console.log(`eid ${ah.executionAsyncId()} tid ${ah.triggerAsyncId()}`);\n});\n// produces:\n// eid 1 tid 0\nObserve that the then() callback claims to have executed in the context of the\nouter scope even though there was an asynchronous hop involved. Also note that\nthe triggerAsyncId value is 0, which means that we are missing context about\nthe resource that caused (triggered) the then() callback to be executed.
Installing async hooks via async_hooks.createHook enables promise execution\ntracking:
const ah = require('async_hooks');\nah.createHook({ init() {} }).enable(); // forces PromiseHooks to be enabled.\nPromise.resolve(1729).then(() => {\n console.log(`eid ${ah.executionAsyncId()} tid ${ah.triggerAsyncId()}`);\n});\n// produces:\n// eid 7 tid 6\nIn this example, adding any actual hook function enabled the tracking of\npromises. There are two promises in the example above; the promise created by\nPromise.resolve() and the promise returned by the call to then(). In the\nexample above, the first promise got the asyncId 6 and the latter got\nasyncId 7. During the execution of the then() callback, we are executing\nin the context of promise with asyncId 7. This promise was triggered by\nasync resource 6.
Another subtlety with promises is that before and after callbacks are run\nonly on chained promises. That means promises not created by then()/catch()\nwill not have the before and after callbacks fired on them. For more details\nsee the details of the V8 PromiseHooks API.
Library developers that handle their own asynchronous resources performing tasks\nlike I/O, connection pooling, or managing callback queues may use the\nAsyncWrap JavaScript API so that all the appropriate callbacks are called.
The class AsyncResource is designed to be extended by the embedder's async\nresources. Using this, users can easily trigger the lifetime events of their\nown resources.
The init hook will trigger when an AsyncResource is instantiated.
The following is an overview of the AsyncResource API.
const { AsyncResource, executionAsyncId } = require('async_hooks');\n\n// AsyncResource() is meant to be extended. Instantiating a\n// new AsyncResource() also triggers init. If triggerAsyncId is omitted then\n// async_hook.executionAsyncId() is used.\nconst asyncResource = new AsyncResource(\n type, { triggerAsyncId: executionAsyncId(), requireManualDestroy: false }\n);\n\n// Run a function in the execution context of the resource. This will\n// * establish the context of the resource\n// * trigger the AsyncHooks before callbacks\n// * call the provided function `fn` with the supplied arguments\n// * trigger the AsyncHooks after callbacks\n// * restore the original execution context\nasyncResource.runInAsyncScope(fn, thisArg, ...args);\n\n// Call AsyncHooks destroy callbacks.\nasyncResource.emitDestroy();\n\n// Return the unique ID assigned to the AsyncResource instance.\nasyncResource.asyncId();\n\n// Return the trigger ID for the AsyncResource instance.\nasyncResource.triggerAsyncId();\nCall the provided function with the provided arguments in the execution context\nof the async resource. This will establish the context, trigger the AsyncHooks\nbefore callbacks, call the function, trigger the AsyncHooks after callbacks, and\nthen restore the original execution context.
" }, { "textRaw": "asyncResource.emitBefore()", "type": "method", "name": "emitBefore", "meta": { "deprecated": [ "v9.6.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`asyncResource.runInAsyncScope()`][] instead.", "signatures": [ { "params": [] } ], "desc": "Call all before callbacks to notify that a new asynchronous execution context\nis being entered. If nested calls to emitBefore() are made, the stack of\nasyncIds will be tracked and properly unwound.
before and after calls must be unwound in the same order that they\nare called. Otherwise, an unrecoverable exception will occur and the process\nwill abort. For this reason, the emitBefore and emitAfter APIs are\nconsidered deprecated. Please use runInAsyncScope, as it provides a much safer\nalternative.
Call all after callbacks. If nested calls to emitBefore() were made, then\nmake sure the stack is unwound properly. Otherwise an error will be thrown.
If the user's callback throws an exception, emitAfter() will automatically be\ncalled for all asyncIds on the stack if the error is handled by a domain or\n'uncaughtException' handler.
before and after calls must be unwound in the same order that they\nare called. Otherwise, an unrecoverable exception will occur and the process\nwill abort. For this reason, the emitBefore and emitAfter APIs are\nconsidered deprecated. Please use runInAsyncScope, as it provides a much safer\nalternative.
Call all destroy hooks. This should only ever be called once. An error will\nbe thrown if it is called more than once. This must be manually called. If\nthe resource is left to be collected by the GC then the destroy hooks will\nnever be called.
Example usage:
\nclass DBQuery extends AsyncResource {\n constructor(db) {\n super('DBQuery');\n this.db = db;\n }\n\n getInfo(query, callback) {\n this.db.get(query, (err, data) => {\n this.runInAsyncScope(callback, null, err, data);\n });\n }\n\n close() {\n this.db = null;\n this.emitDestroy();\n }\n}\nPrior to the introduction of TypedArray, the JavaScript language had no\nmechanism for reading or manipulating streams of binary data. The Buffer class\nwas introduced as part of the Node.js API to enable interaction with octet\nstreams in TCP streams, file system operations, and other contexts.
With TypedArray now available, the Buffer class implements the\nUint8Array API in a manner that is more optimized and suitable for Node.js.
Instances of the Buffer class are similar to arrays of integers but\ncorrespond to fixed-sized, raw memory allocations outside the V8 heap.\nThe size of the Buffer is established when it is created and cannot be\nchanged.
The Buffer class is within the global scope, making it unlikely that one\nwould need to ever use require('buffer').Buffer.
// Creates a zero-filled Buffer of length 10.\nconst buf1 = Buffer.alloc(10);\n\n// Creates a Buffer of length 10, filled with 0x1.\nconst buf2 = Buffer.alloc(10, 1);\n\n// Creates an uninitialized buffer of length 10.\n// This is faster than calling Buffer.alloc() but the returned\n// Buffer instance might contain old data that needs to be\n// overwritten using either fill() or write().\nconst buf3 = Buffer.allocUnsafe(10);\n\n// Creates a Buffer containing [0x1, 0x2, 0x3].\nconst buf4 = Buffer.from([1, 2, 3]);\n\n// Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74].\nconst buf5 = Buffer.from('tést');\n\n// Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].\nconst buf6 = Buffer.from('tést', 'latin1');\nIn versions of Node.js prior to 6.0.0, Buffer instances were created using the\nBuffer constructor function, which allocates the returned Buffer\ndifferently based on what arguments are provided:
Buffer() (e.g. new Buffer(10))\nallocates a new Buffer object of the specified size. Prior to Node.js 8.0.0,\nthe memory allocated for such Buffer instances is not initialized and\ncan contain sensitive data. Such Buffer instances must be subsequently\ninitialized by using either buf.fill(0) or by writing to the\nentire Buffer. While this behavior is intentional to improve performance,\ndevelopment experience has demonstrated that a more explicit distinction is\nrequired between creating a fast-but-uninitialized Buffer versus creating a\nslower-but-safer Buffer. Starting in Node.js 8.0.0, Buffer(num) and\nnew Buffer(num) will return a Buffer with initialized memory.Buffer as the first argument copies the\npassed object's data into the Buffer.ArrayBuffer or a SharedArrayBuffer returns a Buffer that\nshares allocated memory with the given array buffer.Because the behavior of new Buffer() is different depending on the type of the\nfirst argument, security and reliability issues can be inadvertently introduced\ninto applications when argument validation or Buffer initialization is not\nperformed.
To make the creation of Buffer instances more reliable and less error-prone,\nthe various forms of the new Buffer() constructor have been deprecated\nand replaced by separate Buffer.from(), Buffer.alloc(), and\nBuffer.allocUnsafe() methods.
Developers should migrate all existing uses of the new Buffer() constructors\nto one of these new APIs.
Buffer.from(array) returns a new Buffer that contains a copy of the\nprovided octets.Buffer.from(arrayBuffer[, byteOffset[, length]])\nreturns a new Buffer that shares the same allocated memory as the given\nArrayBuffer.Buffer.from(buffer) returns a new Buffer that contains a copy of the\ncontents of the given Buffer.Buffer.from(string[, encoding]) returns a new\nBuffer that contains a copy of the provided string.Buffer.alloc(size[, fill[, encoding]]) returns a new\ninitialized Buffer of the specified size. This method is slower than\nBuffer.allocUnsafe(size) but guarantees that newly\ncreated Buffer instances never contain old data that is potentially\nsensitive.Buffer.allocUnsafe(size) and\nBuffer.allocUnsafeSlow(size) each return a\nnew uninitialized Buffer of the specified size. Because the Buffer is\nuninitialized, the allocated segment of memory might contain old data that is\npotentially sensitive.Buffer instances returned by Buffer.allocUnsafe() may be allocated off\na shared internal memory pool if size is less than or equal to half\nBuffer.poolSize. Instances returned by Buffer.allocUnsafeSlow() never\nuse the shared internal memory pool.
Node.js can be started using the --zero-fill-buffers command line option to\ncause all newly allocated Buffer instances to be zero-filled upon creation by\ndefault, including buffers returned by new Buffer(size),\nBuffer.allocUnsafe(), Buffer.allocUnsafeSlow(), and new SlowBuffer(size). Use of this flag can have a significant negative impact on\nperformance. Use of the --zero-fill-buffers option is recommended only when\nnecessary to enforce that newly allocated Buffer instances cannot contain old\ndata that is potentially sensitive.
$ node --zero-fill-buffers\n> Buffer.allocUnsafe(5);\n<Buffer 00 00 00 00 00>\nWhen calling Buffer.allocUnsafe() and Buffer.allocUnsafeSlow(), the\nsegment of allocated memory is uninitialized (it is not zeroed-out). While\nthis design makes the allocation of memory quite fast, the allocated segment of\nmemory might contain old data that is potentially sensitive. Using a Buffer\ncreated by Buffer.allocUnsafe() without completely overwriting the memory\ncan allow this old data to be leaked when the Buffer memory is read.
While there are clear performance advantages to using Buffer.allocUnsafe(),\nextra care must be taken in order to avoid introducing security\nvulnerabilities into an application.
When string data is stored in or extracted out of a Buffer instance, a\ncharacter encoding may be specified.
const buf = Buffer.from('hello world', 'ascii');\n\nconsole.log(buf.toString('hex'));\n// Prints: 68656c6c6f20776f726c64\nconsole.log(buf.toString('base64'));\n// Prints: aGVsbG8gd29ybGQ=\n\nconsole.log(Buffer.from('fhqwhgads', 'ascii'));\n// Prints: <Buffer 66 68 71 77 68 67 61 64 73>\nconsole.log(Buffer.from('fhqwhgads', 'utf16le'));\n// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>\nThe character encodings currently supported by Node.js include:
\n'ascii' - For 7-bit ASCII data only. This encoding is fast and will strip\nthe high bit if set.
'utf8' - Multibyte encoded Unicode characters. Many web pages and other\ndocument formats use UTF-8.
'utf16le' - 2 or 4 bytes, little-endian encoded Unicode characters.\nSurrogate pairs (U+10000 to U+10FFFF) are supported.
'ucs2' - Alias of 'utf16le'.
'base64' - Base64 encoding. When creating a Buffer from a string,\nthis encoding will also correctly accept \"URL and Filename Safe Alphabet\" as\nspecified in RFC4648, Section 5.
'latin1' - A way of encoding the Buffer into a one-byte encoded string\n(as defined by the IANA in RFC1345,\npage 63, to be the Latin-1 supplement block and C0/C1 control codes).
'binary' - Alias for 'latin1'.
'hex' - Encode each byte as two hexadecimal characters.
Modern Web browsers follow the WHATWG Encoding Standard which aliases\nboth 'latin1' and 'ISO-8859-1' to 'win-1252'. This means that while doing\nsomething like http.get(), if the returned charset is one of those listed in\nthe WHATWG specification it is possible that the server actually returned\n'win-1252'-encoded data, and using 'latin1' encoding may incorrectly decode\nthe characters.
Buffer instances are also Uint8Array instances. However, there are subtle\nincompatibilities with TypedArray. For example, while\nArrayBuffer#slice() creates a copy of the slice, the implementation of\nBuffer#slice() creates a view over the existing Buffer\nwithout copying, making Buffer#slice() far more efficient.
It is also possible to create new TypedArray instances from a Buffer with\nthe following caveats:
The Buffer object's memory is copied to the TypedArray, not shared.
The Buffer object's memory is interpreted as an array of distinct\nelements, and not as a byte array of the target type. That is,\nnew Uint32Array(Buffer.from([1, 2, 3, 4])) creates a 4-element Uint32Array\nwith elements [1, 2, 3, 4], not a Uint32Array with a single element\n[0x1020304] or [0x4030201].
It is possible to create a new Buffer that shares the same allocated memory as\na TypedArray instance by using the TypedArray object's .buffer property.
const arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Copies the contents of `arr`\nconst buf1 = Buffer.from(arr);\n// Shares memory with `arr`\nconst buf2 = Buffer.from(arr.buffer);\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 a0 0f>\n\narr[1] = 6000;\n\nconsole.log(buf1);\n// Prints: <Buffer 88 a0>\nconsole.log(buf2);\n// Prints: <Buffer 88 13 70 17>\nNote that when creating a Buffer using a TypedArray's .buffer, it is\npossible to use only a portion of the underlying ArrayBuffer by passing in\nbyteOffset and length parameters.
const arr = new Uint16Array(20);\nconst buf = Buffer.from(arr.buffer, 0, 16);\n\nconsole.log(buf.length);\n// Prints: 16\nThe Buffer.from() and TypedArray.from() have different signatures and\nimplementations. Specifically, the TypedArray variants accept a second\nargument that is a mapping function that is invoked on every element of the\ntyped array:
TypedArray.from(source[, mapFn[, thisArg]])The Buffer.from() method, however, does not support the use of a mapping\nfunction:
Buffer.from(array)Buffer.from(buffer)Buffer.from(arrayBuffer[, byteOffset[, length]])Buffer.from(string[, encoding])Buffer instances can be iterated over using for..of syntax:
const buf = Buffer.from([1, 2, 3]);\n\n// Prints:\n// 1\n// 2\n// 3\nfor (const b of buf) {\n console.log(b);\n}\nAdditionally, the buf.values(), buf.keys(), and\nbuf.entries() methods can be used to create iterators.
Note that buffer.constants is a property on the buffer module returned by\nrequire('buffer'), not on the Buffer global or a Buffer instance.
On 32-bit architectures, this value is (2^30)-1 (~1GB).\nOn 64-bit architectures, this value is (2^31)-1 (~2GB).
This value is also available as buffer.kMaxLength.
Represents the largest length that a string primitive can have, counted\nin UTF-16 code units.
This value may depend on the JS engine that is being used.
", "shortDesc": "The largest length allowed for a single `string` instance." } ], "type": "module", "displayName": "Buffer Constants" } ], "classes": [ { "textRaw": "Class: Buffer", "type": "class", "name": "Buffer", "desc": "The Buffer class is a global type for dealing with binary data directly.\nIt can be constructed in a variety of ways.
Allocates a new Buffer of size bytes. If fill is undefined, the\nBuffer will be zero-filled.
const buf = Buffer.alloc(5);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\nAllocates a new Buffer of size bytes. If size is larger than\nbuffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is\nthrown. A zero-length Buffer is created if size is 0.
If fill is specified, the allocated Buffer will be initialized by calling\nbuf.fill(fill).
const buf = Buffer.alloc(5, 'a');\n\nconsole.log(buf);\n// Prints: <Buffer 61 61 61 61 61>\nIf both fill and encoding are specified, the allocated Buffer will be\ninitialized by calling buf.fill(fill, encoding).
const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');\n\nconsole.log(buf);\n// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>\nCalling Buffer.alloc() can be significantly slower than the alternative\nBuffer.allocUnsafe() but ensures that the newly created Buffer instance\ncontents will never contain sensitive data.
A TypeError will be thrown if size is not a number.
Allocates a new Buffer of size bytes. If size is larger than\nbuffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is\nthrown. A zero-length Buffer is created if size is 0.
The underlying memory for Buffer instances created in this way is not\ninitialized. The contents of the newly created Buffer are unknown and\nmay contain sensitive data. Use Buffer.alloc() instead to initialize\nBuffer instances with zeroes.
const buf = Buffer.allocUnsafe(10);\n\nconsole.log(buf);\n// Prints: (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>\n\nbuf.fill(0);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>\nA TypeError will be thrown if size is not a number.
Note that the Buffer module pre-allocates an internal Buffer instance of\nsize Buffer.poolSize that is used as a pool for the fast allocation of new\nBuffer instances created using Buffer.allocUnsafe() and the deprecated\nnew Buffer(size) constructor only when size is less than or equal to\nBuffer.poolSize >> 1 (floor of Buffer.poolSize divided by two).
Use of this pre-allocated internal memory pool is a key difference between\ncalling Buffer.alloc(size, fill) vs. Buffer.allocUnsafe(size).fill(fill).\nSpecifically, Buffer.alloc(size, fill) will never use the internal Buffer\npool, while Buffer.allocUnsafe(size).fill(fill) will use the internal\nBuffer pool if size is less than or equal to half Buffer.poolSize. The\ndifference is subtle but can be important when an application requires the\nadditional performance that Buffer.allocUnsafe() provides.
Allocates a new Buffer of size bytes. If size is larger than\nbuffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is\nthrown. A zero-length Buffer is created if size is 0.
The underlying memory for Buffer instances created in this way is not\ninitialized. The contents of the newly created Buffer are unknown and\nmay contain sensitive data. Use buf.fill(0) to initialize\nsuch Buffer instances with zeroes.
When using Buffer.allocUnsafe() to allocate new Buffer instances,\nallocations under 4KB are sliced from a single pre-allocated Buffer. This\nallows applications to avoid the garbage collection overhead of creating many\nindividually allocated Buffer instances. This approach improves both\nperformance and memory usage by eliminating the need to track and clean up as\nmany persistent objects.
However, in the case where a developer may need to retain a small chunk of\nmemory from a pool for an indeterminate amount of time, it may be appropriate\nto create an un-pooled Buffer instance using Buffer.allocUnsafeSlow() and\nthen copying out the relevant bits.
// Need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n let data;\n while (null !== (data = readable.read())) {\n // Allocate for retained data\n const sb = Buffer.allocUnsafeSlow(10);\n\n // Copy the data into the new allocation\n data.copy(sb, 0, 0, 10);\n\n store.push(sb);\n }\n});\nBuffer.allocUnsafeSlow() should be used only as a last resort after a\ndeveloper has observed undue memory retention in their applications.
A TypeError will be thrown if size is not a number.
Returns the actual byte length of a string. This is not the same as\nString.prototype.length since that returns the number of characters in\na string.
For 'base64' and 'hex', this function assumes valid input. For strings that\ncontain non-Base64/Hex-encoded data (e.g. whitespace), the return value might be\ngreater than the length of a Buffer created from the string.
const str = '\\u00bd + \\u00bc = \\u00be';\n\nconsole.log(`${str}: ${str.length} characters, ` +\n `${Buffer.byteLength(str, 'utf8')} bytes`);\n// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes\nWhen string is a Buffer/DataView/TypedArray/ArrayBuffer/\nSharedArrayBuffer, the actual byte length is returned.
Compares buf1 to buf2 typically for the purpose of sorting arrays of\nBuffer instances. This is equivalent to calling\nbuf1.compare(buf2).
const buf1 = Buffer.from('1234');\nconst buf2 = Buffer.from('0123');\nconst arr = [buf1, buf2];\n\nconsole.log(arr.sort(Buffer.compare));\n// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]\n// (This result is equal to: [buf2, buf1])\nReturns a new Buffer which is the result of concatenating all the Buffer\ninstances in the list together.
If the list has no items, or if the totalLength is 0, then a new zero-length\nBuffer is returned.
If totalLength is not provided, it is calculated from the Buffer instances\nin list. This however causes an additional loop to be executed in order to\ncalculate the totalLength, so it is faster to provide the length explicitly if\nit is already known.
If totalLength is provided, it is coerced to an unsigned integer. If the\ncombined length of the Buffers in list exceeds totalLength, the result is\ntruncated to totalLength.
// Create a single `Buffer` from a list of three `Buffer` instances.\n\nconst buf1 = Buffer.alloc(10);\nconst buf2 = Buffer.alloc(14);\nconst buf3 = Buffer.alloc(18);\nconst totalLength = buf1.length + buf2.length + buf3.length;\n\nconsole.log(totalLength);\n// Prints: 42\n\nconst bufA = Buffer.concat([buf1, buf2, buf3], totalLength);\n\nconsole.log(bufA);\n// Prints: <Buffer 00 00 00 00 ...>\nconsole.log(bufA.length);\n// Prints: 42\nAllocates a new Buffer using an array of octets.
// Creates a new Buffer containing UTF-8 bytes of the string 'buffer'\nconst buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\nA TypeError will be thrown if array is not an Array.
This creates a view of the ArrayBuffer without copying the underlying\nmemory. For example, when passed a reference to the .buffer property of a\nTypedArray instance, the newly created Buffer will share the same\nallocated memory as the TypedArray.
const arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Shares memory with `arr`\nconst buf = Buffer.from(arr.buffer);\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 a0 0f>\n\n// Changing the original Uint16Array changes the Buffer also\narr[1] = 6000;\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 70 17>\nThe optional byteOffset and length arguments specify a memory range within\nthe arrayBuffer that will be shared by the Buffer.
const ab = new ArrayBuffer(10);\nconst buf = Buffer.from(ab, 0, 2);\n\nconsole.log(buf.length);\n// Prints: 2\nA TypeError will be thrown if arrayBuffer is not an ArrayBuffer or a\nSharedArrayBuffer.
Copies the passed buffer data onto a new Buffer instance.
const buf1 = Buffer.from('buffer');\nconst buf2 = Buffer.from(buf1);\n\nbuf1[0] = 0x61;\n\nconsole.log(buf1.toString());\n// Prints: auffer\nconsole.log(buf2.toString());\n// Prints: buffer\nA TypeError will be thrown if buffer is not a Buffer.
For objects whose valueOf() function returns a value not strictly equal to\nobject, returns Buffer.from(object.valueOf(), offsetOrEncoding, length).
const buf = Buffer.from(new String('this is a test'));\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\nFor objects that support Symbol.toPrimitive, returns\nBuffer.from(object[Symbol.toPrimitive](), offsetOrEncoding, length).
class Foo {\n [Symbol.toPrimitive]() {\n return 'this is a test';\n }\n}\n\nconst buf = Buffer.from(new Foo(), 'utf8');\n// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>\nCreates a new Buffer containing string. The encoding parameter identifies\nthe character encoding of string.
const buf1 = Buffer.from('this is a tést');\nconst buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');\n\nconsole.log(buf1.toString());\n// Prints: this is a tést\nconsole.log(buf2.toString());\n// Prints: this is a tést\nconsole.log(buf1.toString('ascii'));\n// Prints: this is a tC)st\nA TypeError will be thrown if string is not a string.
Returns true if obj is a Buffer, false otherwise.
Returns true if encoding contains a supported character encoding, or false\notherwise.
This is the size (in bytes) of pre-allocated internal Buffer instances used\nfor pooling. This value may be modified.
The index operator [index] can be used to get and set the octet at position\nindex in buf. The values refer to individual bytes, so the legal value\nrange is between 0x00 and 0xFF (hex) or 0 and 255 (decimal).
This operator is inherited from Uint8Array, so its behavior on out-of-bounds\naccess is the same as UInt8Array - that is, getting returns undefined and\nsetting does nothing.
// Copy an ASCII string into a `Buffer` one byte at a time.\n\nconst str = 'Node.js';\nconst buf = Buffer.allocUnsafe(str.length);\n\nfor (let i = 0; i < str.length; i++) {\n buf[i] = str.charCodeAt(i);\n}\n\nconsole.log(buf.toString('ascii'));\n// Prints: Node.js\nconst arrayBuffer = new ArrayBuffer(16);\nconst buffer = Buffer.from(arrayBuffer);\n\nconsole.log(buffer.buffer === arrayBuffer);\n// Prints: true\nWhen setting byteOffset in Buffer.from(ArrayBuffer, byteOffset, length)\nor sometimes when allocating a buffer smaller than Buffer.poolSize the\nbuffer doesn't start from a zero offset on the underlying ArrayBuffer.
This can cause problems when accessing the underlying ArrayBuffer directly\nusing buf.buffer, as the first bytes in this ArrayBuffer may be unrelated\nto the buf object itself.
A common issue is when casting a Buffer object to a TypedArray object,\nin this case one needs to specify the byteOffset correctly:
// Create a buffer smaller than `Buffer.poolSize`.\nconst nodeBuffer = new Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);\n\n// When casting the Node.js Buffer to an Int8 TypedArray remember to use the\n// byteOffset.\nnew Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);\nReturns the amount of memory allocated for buf in bytes. Note that this\ndoes not necessarily reflect the amount of \"usable\" data within buf.
// Create a `Buffer` and write a shorter ASCII string to it.\n\nconst buf = Buffer.alloc(1234);\n\nconsole.log(buf.length);\n// Prints: 1234\n\nbuf.write('some string', 0, 'ascii');\n\nconsole.log(buf.length);\n// Prints: 1234\nWhile the length property is not immutable, changing the value of length\ncan result in undefined and inconsistent behavior. Applications that wish to\nmodify the length of a Buffer should therefore treat length as read-only and\nuse buf.slice() to create a new Buffer.
let buf = Buffer.allocUnsafe(10);\n\nbuf.write('abcdefghj', 0, 'ascii');\n\nconsole.log(buf.length);\n// Prints: 10\n\nbuf = buf.slice(0, 5);\n\nconsole.log(buf.length);\n// Prints: 5\nThe buf.parent property is a deprecated alias for buf.buffer.
Compares buf with target and returns a number indicating whether buf\ncomes before, after, or is the same as target in sort order.\nComparison is based on the actual sequence of bytes in each Buffer.
0 is returned if target is the same as buf1 is returned if target should come before buf when sorted.-1 is returned if target should come after buf when sorted.const buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('BCD');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.compare(buf1));\n// Prints: 0\nconsole.log(buf1.compare(buf2));\n// Prints: -1\nconsole.log(buf1.compare(buf3));\n// Prints: -1\nconsole.log(buf2.compare(buf1));\n// Prints: 1\nconsole.log(buf2.compare(buf3));\n// Prints: 1\nconsole.log([buf1, buf2, buf3].sort(Buffer.compare));\n// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]\n// (This result is equal to: [buf1, buf3, buf2])\nThe optional targetStart, targetEnd, sourceStart, and sourceEnd\narguments can be used to limit the comparison to specific ranges within target\nand buf respectively.
const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);\nconst buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);\n\nconsole.log(buf1.compare(buf2, 5, 9, 0, 4));\n// Prints: 0\nconsole.log(buf1.compare(buf2, 0, 6, 4));\n// Prints: -1\nconsole.log(buf1.compare(buf2, 5, 6, 5));\n// Prints: 1\nERR_INDEX_OUT_OF_RANGE is thrown if targetStart < 0, sourceStart < 0,\ntargetEnd > target.byteLength, or sourceEnd > source.byteLength.
Copies data from a region of buf to a region in target even if the target\nmemory region overlaps with buf.
// Create two `Buffer` instances.\nconst buf1 = Buffer.allocUnsafe(26);\nconst buf2 = Buffer.allocUnsafe(26).fill('!');\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'\n buf1[i] = i + 97;\n}\n\n// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`\nbuf1.copy(buf2, 8, 16, 20);\n\nconsole.log(buf2.toString('ascii', 0, 25));\n// Prints: !!!!!!!!qrst!!!!!!!!!!!!!\n// Create a `Buffer` and copy data from one region to an overlapping region\n// within the same `Buffer`.\n\nconst buf = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'\n buf[i] = i + 97;\n}\n\nbuf.copy(buf, 0, 4, 10);\n\nconsole.log(buf.toString());\n// Prints: efghijghijklmnopqrstuvwxyz\nCreates and returns an iterator of [index, byte] pairs from the contents of\nbuf.
// Log the entire contents of a `Buffer`.\n\nconst buf = Buffer.from('buffer');\n\nfor (const pair of buf.entries()) {\n console.log(pair);\n}\n// Prints:\n// [0, 98]\n// [1, 117]\n// [2, 102]\n// [3, 102]\n// [4, 101]\n// [5, 114]\nReturns true if both buf and otherBuffer have exactly the same bytes,\nfalse otherwise.
const buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('414243', 'hex');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.equals(buf2));\n// Prints: true\nconsole.log(buf1.equals(buf3));\n// Prints: false\nFills buf with the specified value. If the offset and end are not given,\nthe entire buf will be filled:
// Fill a `Buffer` with the ASCII character 'h'.\n\nconst b = Buffer.allocUnsafe(50).fill('h');\n\nconsole.log(b.toString());\n// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh\nvalue is coerced to a uint32 value if it is not a string, Buffer, or\ninteger. If the resulting integer is greater than 255 (decimal), buf will be\nfilled with value & 255.
If the final write of a fill() operation falls on a multi-byte character,\nthen only the bytes of that character that fit into buf are written:
// Fill a `Buffer` with a two-byte character.\n\nconsole.log(Buffer.allocUnsafe(3).fill('\\u0222'));\n// Prints: <Buffer c8 a2 c8>\nIf value contains invalid characters, it is truncated; if no valid\nfill data remains, an exception is thrown:
const buf = Buffer.allocUnsafe(5);\n\nconsole.log(buf.fill('a'));\n// Prints: <Buffer 61 61 61 61 61>\nconsole.log(buf.fill('aazz', 'hex'));\n// Prints: <Buffer aa aa aa aa aa>\nconsole.log(buf.fill('zz', 'hex'));\n// Throws an exception.\nEquivalent to buf.indexOf() !== -1.
const buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.includes('this'));\n// Prints: true\nconsole.log(buf.includes('is'));\n// Prints: true\nconsole.log(buf.includes(Buffer.from('a buffer')));\n// Prints: true\nconsole.log(buf.includes(97));\n// Prints: true (97 is the decimal ASCII value for 'a')\nconsole.log(buf.includes(Buffer.from('a buffer example')));\n// Prints: false\nconsole.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: true\nconsole.log(buf.includes('this', 4));\n// Prints: false\nIf value is:
value is interpreted according to the character encoding in\nencoding.Buffer or Uint8Array, value will be used in its entirety.\nTo compare a partial Buffer, use buf.slice().value will be interpreted as an unsigned 8-bit integer\nvalue between 0 and 255.const buf = Buffer.from('this is a buffer');\n\nconsole.log(buf.indexOf('this'));\n// Prints: 0\nconsole.log(buf.indexOf('is'));\n// Prints: 2\nconsole.log(buf.indexOf(Buffer.from('a buffer')));\n// Prints: 8\nconsole.log(buf.indexOf(97));\n// Prints: 8 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.indexOf(Buffer.from('a buffer example')));\n// Prints: -1\nconsole.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));\n// Prints: 8\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.indexOf('\\u03a3', 0, 'utf16le'));\n// Prints: 4\nconsole.log(utf16Buffer.indexOf('\\u03a3', -4, 'utf16le'));\n// Prints: 6\nIf value is not a string, number, or Buffer, this method will throw a\nTypeError. If value is a number, it will be coerced to a valid byte value,\nan integer between 0 and 255.
If byteOffset is not a number, it will be coerced to a number. If the result\nof coercion is NaN or 0, then the entire buffer will be searched. This\nbehavior matches String#indexOf().
const b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte\n// Prints: 2, equivalent to searching for 99 or 'c'\nconsole.log(b.indexOf(99.9));\nconsole.log(b.indexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN or 0\n// Prints: 1, searching the whole buffer\nconsole.log(b.indexOf('b', undefined));\nconsole.log(b.indexOf('b', {}));\nconsole.log(b.indexOf('b', null));\nconsole.log(b.indexOf('b', []));\nIf value is an empty string or empty Buffer and byteOffset is less\nthan buf.length, byteOffset will be returned. If value is empty and\nbyteOffset is at least buf.length, buf.length will be returned.
Creates and returns an iterator of buf keys (indices).
const buf = Buffer.from('buffer');\n\nfor (const key of buf.keys()) {\n console.log(key);\n}\n// Prints:\n// 0\n// 1\n// 2\n// 3\n// 4\n// 5\nIdentical to buf.indexOf(), except the last occurrence of value is found\nrather than the first occurrence.
const buf = Buffer.from('this buffer is a buffer');\n\nconsole.log(buf.lastIndexOf('this'));\n// Prints: 0\nconsole.log(buf.lastIndexOf('buffer'));\n// Prints: 17\nconsole.log(buf.lastIndexOf(Buffer.from('buffer')));\n// Prints: 17\nconsole.log(buf.lastIndexOf(97));\n// Prints: 15 (97 is the decimal ASCII value for 'a')\nconsole.log(buf.lastIndexOf(Buffer.from('yolo')));\n// Prints: -1\nconsole.log(buf.lastIndexOf('buffer', 5));\n// Prints: 5\nconsole.log(buf.lastIndexOf('buffer', 4));\n// Prints: -1\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'utf16le');\n\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', undefined, 'utf16le'));\n// Prints: 6\nconsole.log(utf16Buffer.lastIndexOf('\\u03a3', -5, 'utf16le'));\n// Prints: 4\nIf value is not a string, number, or Buffer, this method will throw a\nTypeError. If value is a number, it will be coerced to a valid byte value,\nan integer between 0 and 255.
If byteOffset is not a number, it will be coerced to a number. Any arguments\nthat coerce to NaN, like {} or undefined, will search the whole buffer.\nThis behavior matches String#lastIndexOf().
const b = Buffer.from('abcdef');\n\n// Passing a value that's a number, but not a valid byte\n// Prints: 2, equivalent to searching for 99 or 'c'\nconsole.log(b.lastIndexOf(99.9));\nconsole.log(b.lastIndexOf(256 + 99));\n\n// Passing a byteOffset that coerces to NaN\n// Prints: 1, searching the whole buffer\nconsole.log(b.lastIndexOf('b', undefined));\nconsole.log(b.lastIndexOf('b', {}));\n\n// Passing a byteOffset that coerces to 0\n// Prints: -1, equivalent to passing 0\nconsole.log(b.lastIndexOf('b', null));\nconsole.log(b.lastIndexOf('b', []));\nIf value is an empty string or empty Buffer, byteOffset will be returned.
Reads a 64-bit double from buf at the specified offset with specified\nendian format (readDoubleBE() returns big endian, readDoubleLE() returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\nconsole.log(buf.readDoubleLE(0));\n// Prints: 5.447603722011605e-270\nconsole.log(buf.readDoubleLE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a 64-bit double from buf at the specified offset with specified\nendian format (readDoubleBE() returns big endian, readDoubleLE() returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);\n\nconsole.log(buf.readDoubleBE(0));\n// Prints: 8.20788039913184e-304\nconsole.log(buf.readDoubleLE(0));\n// Prints: 5.447603722011605e-270\nconsole.log(buf.readDoubleLE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a 32-bit float from buf at the specified offset with specified\nendian format (readFloatBE() returns big endian, readFloatLE() returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\nconsole.log(buf.readFloatLE(0));\n// Prints: 1.539989614439558e-36\nconsole.log(buf.readFloatLE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a 32-bit float from buf at the specified offset with specified\nendian format (readFloatBE() returns big endian, readFloatLE() returns\nlittle endian).
const buf = Buffer.from([1, 2, 3, 4]);\n\nconsole.log(buf.readFloatBE(0));\n// Prints: 2.387939260590663e-38\nconsole.log(buf.readFloatLE(0));\n// Prints: 1.539989614439558e-36\nconsole.log(buf.readFloatLE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a signed 8-bit integer from buf at the specified offset.
Integers read from a Buffer are interpreted as two's complement signed values.
const buf = Buffer.from([-1, 5]);\n\nconsole.log(buf.readInt8(0));\n// Prints: -1\nconsole.log(buf.readInt8(1));\n// Prints: 5\nconsole.log(buf.readInt8(2));\n// Throws ERR_OUT_OF_RANGE\nReads a signed 16-bit integer from buf at the specified offset with\nthe specified endian format (readInt16BE() returns big endian,\nreadInt16LE() returns little endian).
Integers read from a Buffer are interpreted as two's complement signed values.
const buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\nconsole.log(buf.readInt16LE(0));\n// Prints: 1280\nconsole.log(buf.readInt16LE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a signed 16-bit integer from buf at the specified offset with\nthe specified endian format (readInt16BE() returns big endian,\nreadInt16LE() returns little endian).
Integers read from a Buffer are interpreted as two's complement signed values.
const buf = Buffer.from([0, 5]);\n\nconsole.log(buf.readInt16BE(0));\n// Prints: 5\nconsole.log(buf.readInt16LE(0));\n// Prints: 1280\nconsole.log(buf.readInt16LE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a signed 32-bit integer from buf at the specified offset with\nthe specified endian format (readInt32BE() returns big endian,\nreadInt32LE() returns little endian).
Integers read from a Buffer are interpreted as two's complement signed values.
const buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\nconsole.log(buf.readInt32LE(0));\n// Prints: 83886080\nconsole.log(buf.readInt32LE(1));\n// Throws ERR_OUT_OF_RANGE\nReads a signed 32-bit integer from buf at the specified offset with\nthe specified endian format (readInt32BE() returns big endian,\nreadInt32LE() returns little endian).
Integers read from a Buffer are interpreted as two's complement signed values.
const buf = Buffer.from([0, 0, 0, 5]);\n\nconsole.log(buf.readInt32BE(0));\n// Prints: 5\nconsole.log(buf.readInt32LE(0));\n// Prints: 83886080\nconsole.log(buf.readInt32LE(1));\n// Throws ERR_OUT_OF_RANGE\nReads byteLength number of bytes from buf at the specified offset\nand interprets the result as a two's complement signed value. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\nconsole.log(buf.readIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readIntBE(1, 6).toString(16));\n// Throws ERR_INDEX_OUT_OF_RANGE\nconsole.log(buf.readIntBE(1, 0).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads byteLength number of bytes from buf at the specified offset\nand interprets the result as a two's complement signed value. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readIntLE(0, 6).toString(16));\n// Prints: -546f87a9cbee\nconsole.log(buf.readIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readIntBE(1, 6).toString(16));\n// Throws ERR_INDEX_OUT_OF_RANGE\nconsole.log(buf.readIntBE(1, 0).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads an unsigned 8-bit integer from buf at the specified offset.
const buf = Buffer.from([1, -2]);\n\nconsole.log(buf.readUInt8(0));\n// Prints: 1\nconsole.log(buf.readUInt8(1));\n// Prints: 254\nconsole.log(buf.readUInt8(2));\n// Throws ERR_OUT_OF_RANGE\nReads an unsigned 16-bit integer from buf at the specified offset with\nspecified endian format (readUInt16BE() returns big endian, readUInt16LE()\nreturns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\nconsole.log(buf.readUInt16LE(1).toString(16));\n// Prints: 5634\nconsole.log(buf.readUInt16LE(2).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads an unsigned 16-bit integer from buf at the specified offset with\nspecified endian format (readUInt16BE() returns big endian, readUInt16LE()\nreturns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56]);\n\nconsole.log(buf.readUInt16BE(0).toString(16));\n// Prints: 1234\nconsole.log(buf.readUInt16LE(0).toString(16));\n// Prints: 3412\nconsole.log(buf.readUInt16BE(1).toString(16));\n// Prints: 3456\nconsole.log(buf.readUInt16LE(1).toString(16));\n// Prints: 5634\nconsole.log(buf.readUInt16LE(2).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads an unsigned 32-bit integer from buf at the specified offset with\nspecified endian format (readUInt32BE() returns big endian,\nreadUInt32LE() returns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\nconsole.log(buf.readUInt32LE(0).toString(16));\n// Prints: 78563412\nconsole.log(buf.readUInt32LE(1).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads an unsigned 32-bit integer from buf at the specified offset with\nspecified endian format (readUInt32BE() returns big endian,\nreadUInt32LE() returns little endian).
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);\n\nconsole.log(buf.readUInt32BE(0).toString(16));\n// Prints: 12345678\nconsole.log(buf.readUInt32LE(0).toString(16));\n// Prints: 78563412\nconsole.log(buf.readUInt32LE(1).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads byteLength number of bytes from buf at the specified offset\nand interprets the result as an unsigned integer. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\nconsole.log(buf.readUIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReads byteLength number of bytes from buf at the specified offset\nand interprets the result as an unsigned integer. Supports up to 48\nbits of accuracy.
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);\n\nconsole.log(buf.readUIntBE(0, 6).toString(16));\n// Prints: 1234567890ab\nconsole.log(buf.readUIntLE(0, 6).toString(16));\n// Prints: ab9078563412\nconsole.log(buf.readUIntBE(1, 6).toString(16));\n// Throws ERR_OUT_OF_RANGE\nReturns a new Buffer that references the same memory as the original, but\noffset and cropped by the start and end indices.
Specifying end greater than buf.length will return the same result as\nthat of end equal to buf.length.
Modifying the new Buffer slice will modify the memory in the original Buffer\nbecause the allocated memory of the two objects overlap.
// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte\n// from the original `Buffer`.\n\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'\n buf1[i] = i + 97;\n}\n\nconst buf2 = buf1.slice(0, 3);\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: abc\n\nbuf1[0] = 33;\n\nconsole.log(buf2.toString('ascii', 0, buf2.length));\n// Prints: !bc\nSpecifying negative indexes causes the slice to be generated relative to the\nend of buf rather than the beginning.
const buf = Buffer.from('buffer');\n\nconsole.log(buf.slice(-6, -1).toString());\n// Prints: buffe\n// (Equivalent to buf.slice(0, 5))\n\nconsole.log(buf.slice(-6, -2).toString());\n// Prints: buff\n// (Equivalent to buf.slice(0, 4))\n\nconsole.log(buf.slice(-5, -2).toString());\n// Prints: uff\n// (Equivalent to buf.slice(1, 4))\nInterprets buf as an array of unsigned 16-bit integers and swaps the\nbyte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is\nnot a multiple of 2.
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap16();\n\nconsole.log(buf1);\n// Prints: <Buffer 02 01 04 03 06 05 08 07>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap16();\n// Throws ERR_INVALID_BUFFER_SIZE\nOne convenient use of buf.swap16() is to perform a fast in-place conversion\nbetween UTF-16 little-endian and UTF-16 big-endian:
const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');\nbuf.swap16(); // Convert to big-endian UTF-16 text.\nInterprets buf as an array of unsigned 32-bit integers and swaps the\nbyte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is\nnot a multiple of 4.
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap32();\n\nconsole.log(buf1);\n// Prints: <Buffer 04 03 02 01 08 07 06 05>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap32();\n// Throws ERR_INVALID_BUFFER_SIZE\nInterprets buf as an array of 64-bit numbers and swaps byte order in-place.\nThrows ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 8.
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\n\nconsole.log(buf1);\n// Prints: <Buffer 01 02 03 04 05 06 07 08>\n\nbuf1.swap64();\n\nconsole.log(buf1);\n// Prints: <Buffer 08 07 06 05 04 03 02 01>\n\nconst buf2 = Buffer.from([0x1, 0x2, 0x3]);\n\nbuf2.swap64();\n// Throws ERR_INVALID_BUFFER_SIZE\nNote that JavaScript cannot encode 64-bit integers. This method is intended\nfor working with 64-bit floats.
" }, { "textRaw": "buf.toJSON()", "type": "method", "name": "toJSON", "meta": { "added": [ "v0.9.2" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "Returns a JSON representation of buf. JSON.stringify() implicitly calls\nthis function when stringifying a Buffer instance.
const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);\nconst json = JSON.stringify(buf);\n\nconsole.log(json);\n// Prints: {\"type\":\"Buffer\",\"data\":[1,2,3,4,5]}\n\nconst copy = JSON.parse(json, (key, value) => {\n return value && value.type === 'Buffer' ?\n Buffer.from(value.data) :\n value;\n});\n\nconsole.log(copy);\n// Prints: <Buffer 01 02 03 04 05>\nDecodes buf to a string according to the specified character encoding in\nencoding. start and end may be passed to decode only a subset of buf.
The maximum length of a string instance (in UTF-16 code units) is available\nas buffer.constants.MAX_STRING_LENGTH.
const buf1 = Buffer.allocUnsafe(26);\n\nfor (let i = 0; i < 26; i++) {\n // 97 is the decimal ASCII value for 'a'\n buf1[i] = i + 97;\n}\n\nconsole.log(buf1.toString('ascii'));\n// Prints: abcdefghijklmnopqrstuvwxyz\nconsole.log(buf1.toString('ascii', 0, 5));\n// Prints: abcde\n\nconst buf2 = Buffer.from('tést');\n\nconsole.log(buf2.toString('hex'));\n// Prints: 74c3a97374\nconsole.log(buf2.toString('utf8', 0, 3));\n// Prints: té\nconsole.log(buf2.toString(undefined, 0, 3));\n// Prints: té\nCreates and returns an iterator for buf values (bytes). This function is\ncalled automatically when a Buffer is used in a for..of statement.
const buf = Buffer.from('buffer');\n\nfor (const value of buf.values()) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n\nfor (const value of buf) {\n console.log(value);\n}\n// Prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\nWrites string to buf at offset according to the character encoding in\nencoding. The length parameter is the number of bytes to write. If buf did\nnot contain enough space to fit the entire string, only part of string will be\nwritten. However, partially encoded characters will not be written.
const buf = Buffer.alloc(256);\n\nconst len = buf.write('\\u00bd + \\u00bc = \\u00be', 0);\n\nconsole.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);\n// Prints: 12 bytes: ½ + ¼ = ¾\nWrites value to buf at the specified offset with specified endian\nformat (writeDoubleBE() writes big endian, writeDoubleLE() writes little\nendian). value should be a valid 64-bit double. Behavior is undefined when\nvalue is anything other than a 64-bit double.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleBE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>\n\nbuf.writeDoubleLE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>\nWrites value to buf at the specified offset with specified endian\nformat (writeDoubleBE() writes big endian, writeDoubleLE() writes little\nendian). value should be a valid 64-bit double. Behavior is undefined when\nvalue is anything other than a 64-bit double.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeDoubleBE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>\n\nbuf.writeDoubleLE(123.456, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>\nWrites value to buf at the specified offset with specified endian\nformat (writeFloatBE() writes big endian, writeFloatLE() writes little\nendian). value should be a valid 32-bit float. Behavior is undefined when\nvalue is anything other than a 32-bit float.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer bb fe 4a 4f>\nWrites value to buf at the specified offset with specified endian\nformat (writeFloatBE() writes big endian, writeFloatLE() writes little\nendian). value should be a valid 32-bit float. Behavior is undefined when\nvalue is anything other than a 32-bit float.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer 4f 4a fe bb>\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n// Prints: <Buffer bb fe 4a 4f>\nWrites value to buf at the specified offset. value should be a valid\nsigned 8-bit integer. Behavior is undefined when value is anything other than\na signed 8-bit integer.
value is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(2);\n\nbuf.writeInt8(2, 0);\nbuf.writeInt8(-2, 1);\n\nconsole.log(buf);\n// Prints: <Buffer 02 fe>\nWrites value to buf at the specified offset with specified endian\nformat (writeInt16BE() writes big endian, writeInt16LE() writes little\nendian). value should be a valid signed 16-bit integer. Behavior is\nundefined when value is anything other than a signed 16-bit integer.
value is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt16BE(0x0102, 0);\nbuf.writeInt16LE(0x0304, 2);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 04 03>\nWrites value to buf at the specified offset with specified endian\nformat (writeInt16BE() writes big endian, writeInt16LE() writes little\nendian). value should be a valid signed 16-bit integer. Behavior is\nundefined when value is anything other than a signed 16-bit integer.
value is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeInt16BE(0x0102, 0);\nbuf.writeInt16LE(0x0304, 2);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 04 03>\nWrites value to buf at the specified offset with specified endian\nformat (writeInt32BE() writes big endian, writeInt32LE() writes little\nendian). value should be a valid signed 32-bit integer. Behavior is\nundefined when value is anything other than a signed 32-bit integer.
value is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeInt32BE(0x01020304, 0);\nbuf.writeInt32LE(0x05060708, 4);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 08 07 06 05>\nWrites value to buf at the specified offset with specified endian\nformat (writeInt32BE() writes big endian, writeInt32LE() writes little\nendian). value should be a valid signed 32-bit integer. Behavior is\nundefined when value is anything other than a signed 32-bit integer.
value is interpreted and written as a two's complement signed integer.
const buf = Buffer.allocUnsafe(8);\n\nbuf.writeInt32BE(0x01020304, 0);\nbuf.writeInt32LE(0x05060708, 4);\n\nconsole.log(buf);\n// Prints: <Buffer 01 02 03 04 08 07 06 05>\nWrites byteLength bytes of value to buf at the specified offset.\nSupports up to 48 bits of accuracy. Behavior is undefined when value is\nanything other than a signed integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\nWrites byteLength bytes of value to buf at the specified offset.\nSupports up to 48 bits of accuracy. Behavior is undefined when value is\nanything other than a signed integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\nWrites value to buf at the specified offset. value should be a\nvalid unsigned 8-bit integer. Behavior is undefined when value is anything\nother than an unsigned 8-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt8(0x3, 0);\nbuf.writeUInt8(0x4, 1);\nbuf.writeUInt8(0x23, 2);\nbuf.writeUInt8(0x42, 3);\n\nconsole.log(buf);\n// Prints: <Buffer 03 04 23 42>\nWrites value to buf at the specified offset with specified endian\nformat (writeUInt16BE() writes big endian, writeUInt16LE() writes little\nendian). value should be a valid unsigned 16-bit integer. Behavior is\nundefined when value is anything other than an unsigned 16-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer de ad be ef>\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer ad de ef be>\nWrites value to buf at the specified offset with specified endian\nformat (writeUInt16BE() writes big endian, writeUInt16LE() writes little\nendian). value should be a valid unsigned 16-bit integer. Behavior is\nundefined when value is anything other than an unsigned 16-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer de ad be ef>\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n// Prints: <Buffer ad de ef be>\nWrites value to buf at the specified offset with specified endian\nformat (writeUInt32BE() writes big endian, writeUInt32LE() writes little\nendian). value should be a valid unsigned 32-bit integer. Behavior is\nundefined when value is anything other than an unsigned 32-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer ce fa ed fe>\nWrites value to buf at the specified offset with specified endian\nformat (writeUInt32BE() writes big endian, writeUInt32LE() writes little\nendian). value should be a valid unsigned 32-bit integer. Behavior is\nundefined when value is anything other than an unsigned 32-bit integer.
const buf = Buffer.allocUnsafe(4);\n\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer fe ed fa ce>\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n// Prints: <Buffer ce fa ed fe>\nWrites byteLength bytes of value to buf at the specified offset.\nSupports up to 48 bits of accuracy. Behavior is undefined when value is\nanything other than an unsigned integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeUIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\nWrites byteLength bytes of value to buf at the specified offset.\nSupports up to 48 bits of accuracy. Behavior is undefined when value is\nanything other than an unsigned integer.
const buf = Buffer.allocUnsafe(6);\n\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer 12 34 56 78 90 ab>\n\nbuf.writeUIntLE(0x1234567890ab, 0, 6);\n\nconsole.log(buf);\n// Prints: <Buffer ab 90 78 56 34 12>\nAllocates a new Buffer using an array of octets.
// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'\nconst buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);\nThis creates a view of the ArrayBuffer or SharedArrayBuffer without\ncopying the underlying memory. For example, when passed a reference to the\n.buffer property of a TypedArray instance, the newly created Buffer will\nshare the same allocated memory as the TypedArray.
The optional byteOffset and length arguments specify a memory range within\nthe arrayBuffer that will be shared by the Buffer.
const arr = new Uint16Array(2);\n\narr[0] = 5000;\narr[1] = 4000;\n\n// Shares memory with `arr`\nconst buf = new Buffer(arr.buffer);\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 a0 0f>\n\n// Changing the original Uint16Array changes the Buffer also\narr[1] = 6000;\n\nconsole.log(buf);\n// Prints: <Buffer 88 13 70 17>\nCopies the passed buffer data onto a new Buffer instance.
const buf1 = new Buffer('buffer');\nconst buf2 = new Buffer(buf1);\n\nbuf1[0] = 0x61;\n\nconsole.log(buf1.toString());\n// Prints: auffer\nconsole.log(buf2.toString());\n// Prints: buffer\nAllocates a new Buffer of size bytes. If size is larger than\nbuffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is\nthrown. A zero-length Buffer is created if size is 0.
Prior to Node.js 8.0.0, the underlying memory for Buffer instances\ncreated in this way is not initialized. The contents of a newly created\nBuffer are unknown and may contain sensitive data. Use\nBuffer.alloc(size) instead to initialize a Buffer\nwith zeroes.
const buf = new Buffer(10);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>\nCreates a new Buffer containing string. The encoding parameter identifies\nthe character encoding of string.
const buf1 = new Buffer('this is a tést');\nconst buf2 = new Buffer('7468697320697320612074c3a97374', 'hex');\n\nconsole.log(buf1.toString());\n// Prints: this is a tést\nconsole.log(buf2.toString());\n// Prints: this is a tést\nconsole.log(buf1.toString('ascii'));\n// Prints: this is a tC)st\nReturns an un-pooled Buffer.
In order to avoid the garbage collection overhead of creating many individually\nallocated Buffer instances, by default allocations under 4KB are sliced from a\nsingle larger allocated object.
In the case where a developer may need to retain a small chunk of memory from a\npool for an indeterminate amount of time, it may be appropriate to create an\nun-pooled Buffer instance using SlowBuffer then copy out the relevant bits.
// Need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n let data;\n while (null !== (data = readable.read())) {\n // Allocate for retained data\n const sb = SlowBuffer(10);\n\n // Copy the data into the new allocation\n data.copy(sb, 0, 0, 10);\n\n store.push(sb);\n }\n});\nUse of SlowBuffer should be used only as a last resort after a developer\nhas observed undue memory retention in their applications.
Allocates a new Buffer of size bytes. If size is larger than\nbuffer.constants.MAX_LENGTH or smaller than 0, ERR_INVALID_OPT_VALUE is\nthrown. A zero-length Buffer is created if size is 0.
The underlying memory for SlowBuffer instances is not initialized. The\ncontents of a newly created SlowBuffer are unknown and may contain sensitive\ndata. Use buf.fill(0) to initialize a SlowBuffer with\nzeroes.
const { SlowBuffer } = require('buffer');\n\nconst buf = new SlowBuffer(5);\n\nconsole.log(buf);\n// Prints: (contents may vary): <Buffer 78 e0 82 02 01>\n\nbuf.fill(0);\n\nconsole.log(buf);\n// Prints: <Buffer 00 00 00 00 00>\nReturns the maximum number of bytes that will be returned when\nbuf.inspect() is called. This can be overridden by user modules. See\nutil.inspect() for more details on buf.inspect() behavior.
Note that this is a property on the buffer module returned by\nrequire('buffer'), not on the Buffer global or a Buffer instance.
An alias for buffer.constants.MAX_LENGTH.
Note that this is a property on the buffer module returned by\nrequire('buffer'), not on the Buffer global or a Buffer instance.
Re-encodes the given Buffer or Uint8Array instance from one character\nencoding to another. Returns a new Buffer instance.
Throws if the fromEnc or toEnc specify invalid character encodings or if\nconversion from fromEnc to toEnc is not permitted.
Encodings supported by buffer.transcode() are: 'ascii', 'utf8',\n'utf16le', 'ucs2', 'latin1', and 'binary'.
The transcoding process will use substitution characters if a given byte\nsequence cannot be adequately represented in the target encoding. For instance:
\nconst buffer = require('buffer');\n\nconst newBuf = buffer.transcode(Buffer.from('€'), 'utf8', 'ascii');\nconsole.log(newBuf.toString('ascii'));\n// Prints: '?'\nBecause the Euro (€) sign is not representable in US-ASCII, it is replaced\nwith ? in the transcoded Buffer.
Note that this is a property on the buffer module returned by\nrequire('buffer'), not on the Buffer global or a Buffer instance.
\n\nStability: 2 - Stable
\n
The child_process module provides the ability to spawn child processes in\na manner that is similar, but not identical, to popen(3). This capability\nis primarily provided by the child_process.spawn() function:
const { spawn } = require('child_process');\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.log(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});\nBy default, pipes for stdin, stdout, and stderr are established between\nthe parent Node.js process and the spawned child. These pipes have\nlimited (and platform-specific) capacity. If the child process writes to\nstdout in excess of that limit without the output being captured, the child\nprocess will block waiting for the pipe buffer to accept more data. This is\nidentical to the behavior of pipes in the shell. Use the { stdio: 'ignore' }\noption if the output will not be consumed.
The child_process.spawn() method spawns the child process asynchronously,\nwithout blocking the Node.js event loop. The child_process.spawnSync()\nfunction provides equivalent functionality in a synchronous manner that blocks\nthe event loop until the spawned process either exits or is terminated.
For convenience, the child_process module provides a handful of synchronous\nand asynchronous alternatives to child_process.spawn() and\nchild_process.spawnSync(). Note that each of these alternatives are\nimplemented on top of child_process.spawn() or child_process.spawnSync().
child_process.exec(): spawns a shell and runs a command within that shell,\npassing the stdout and stderr to a callback function when complete.child_process.execFile(): similar to child_process.exec() except that\nit spawns the command directly without first spawning a shell by default.child_process.fork(): spawns a new Node.js process and invokes a\nspecified module with an IPC communication channel established that allows\nsending messages between parent and child.child_process.execSync(): a synchronous version of\nchild_process.exec() that will block the Node.js event loop.child_process.execFileSync(): a synchronous version of\nchild_process.execFile() that will block the Node.js event loop.For certain use cases, such as automating shell scripts, the\nsynchronous counterparts may be more convenient. In many cases, however,\nthe synchronous methods can have significant impact on performance due to\nstalling the event loop while spawned processes complete.
", "modules": [ { "textRaw": "Asynchronous Process Creation", "name": "asynchronous_process_creation", "desc": "The child_process.spawn(), child_process.fork(), child_process.exec(),\nand child_process.execFile() methods all follow the idiomatic asynchronous\nprogramming pattern typical of other Node.js APIs.
Each of the methods returns a ChildProcess instance. These objects\nimplement the Node.js EventEmitter API, allowing the parent process to\nregister listener functions that are called when certain events occur during\nthe life cycle of the child process.
The child_process.exec() and child_process.execFile() methods additionally\nallow for an optional callback function to be specified that is invoked\nwhen the child process terminates.
The importance of the distinction between child_process.exec() and\nchild_process.execFile() can vary based on platform. On Unix-type operating\nsystems (Unix, Linux, macOS) child_process.execFile() can be more efficient\nbecause it does not spawn a shell by default. On Windows, however, .bat and .cmd\nfiles are not executable on their own without a terminal, and therefore cannot\nbe launched using child_process.execFile(). When running on Windows, .bat\nand .cmd files can be invoked using child_process.spawn() with the shell\noption set, with child_process.exec(), or by spawning cmd.exe and passing\nthe .bat or .cmd file as an argument (which is what the shell option and\nchild_process.exec() do). In any case, if the script filename contains\nspaces it needs to be quoted.
// On Windows Only ...\nconst { spawn } = require('child_process');\nconst bat = spawn('cmd.exe', ['/c', 'my.bat']);\n\nbat.stdout.on('data', (data) => {\n console.log(data.toString());\n});\n\nbat.stderr.on('data', (data) => {\n console.log(data.toString());\n});\n\nbat.on('exit', (code) => {\n console.log(`Child exited with code ${code}`);\n});\n// OR...\nconst { exec } = require('child_process');\nexec('my.bat', (err, stdout, stderr) => {\n if (err) {\n console.error(err);\n return;\n }\n console.log(stdout);\n});\n\n// Script with spaces in the filename:\nconst bat = spawn('\"my script.cmd\"', ['a', 'b'], { shell: true });\n// or:\nexec('\"my script.cmd\" a b', (err, stdout, stderr) => {\n // ...\n});\nSpawns a shell then executes the command within that shell, buffering any\ngenerated output. The command string passed to the exec function is processed\ndirectly by the shell and special characters (vary based on\nshell)\nneed to be dealt with accordingly:
exec('\"/path/to/test file/test.sh\" arg1 arg2');\n// Double quotes are used so that the space in the path is not interpreted as\n// multiple arguments\n\nexec('echo \"The \\\\$HOME variable is $HOME\"');\n// The $HOME variable is escaped in the first instance, but not in the second\nNever pass unsanitized user input to this function. Any input containing shell\nmetacharacters may be used to trigger arbitrary command execution.
\nIf a callback function is provided, it is called with the arguments\n(error, stdout, stderr). On success, error will be null. On error,\nerror will be an instance of Error. The error.code property will be\nthe exit code of the child process while error.signal will be set to the\nsignal that terminated the process. Any exit code other than 0 is considered\nto be an error.
The stdout and stderr arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding is 'buffer', or an unrecognized character\nencoding, Buffer objects will be passed to the callback instead.
const { exec } = require('child_process');\nexec('cat *.js missing_file | wc -l', (error, stdout, stderr) => {\n if (error) {\n console.error(`exec error: ${error}`);\n return;\n }\n console.log(`stdout: ${stdout}`);\n console.log(`stderr: ${stderr}`);\n});\nIf timeout is greater than 0, the parent will send the signal\nidentified by the killSignal property (the default is 'SIGTERM') if the\nchild runs longer than timeout milliseconds.
Unlike the exec(3) POSIX system call, child_process.exec() does not replace\nthe existing process and uses a shell to execute the command.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with stdout and stderr properties. In case of an\nerror (including any error resulting in an exit code other than 0), a rejected\npromise is returned, with the same error object given in the callback, but\nwith an additional two properties stdout and stderr.
const util = require('util');\nconst exec = util.promisify(require('child_process').exec);\n\nasync function lsExample() {\n const { stdout, stderr } = await exec('ls');\n console.log('stdout:', stdout);\n console.log('stderr:', stderr);\n}\nlsExample();\nThe child_process.execFile() function is similar to child_process.exec()\nexcept that it does not spawn a shell by default. Rather, the specified executable file\nis spawned directly as a new process making it slightly more efficient than\nchild_process.exec().
The same options as child_process.exec() are supported. Since a shell is not\nspawned, behaviors such as I/O redirection and file globbing are not supported.
const { execFile } = require('child_process');\nconst child = execFile('node', ['--version'], (error, stdout, stderr) => {\n if (error) {\n throw error;\n }\n console.log(stdout);\n});\nThe stdout and stderr arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding is 'buffer', or an unrecognized character\nencoding, Buffer objects will be passed to the callback instead.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with stdout and stderr properties. In case of an\nerror (including any error resulting in an exit code other than 0), a rejected\npromise is returned, with the same error object given in the\ncallback, but with an additional two properties stdout and stderr.
const util = require('util');\nconst execFile = util.promisify(require('child_process').execFile);\nasync function getVersion() {\n const { stdout } = await execFile('node', ['--version']);\n console.log(stdout);\n}\ngetVersion();\nIf the shell option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
The child_process.fork() method is a special case of\nchild_process.spawn() used specifically to spawn new Node.js processes.\nLike child_process.spawn(), a ChildProcess object is returned. The returned\nChildProcess will have an additional communication channel built-in that\nallows messages to be passed back and forth between the parent and child. See\nsubprocess.send() for details.
It is important to keep in mind that spawned Node.js child processes are\nindependent of the parent with exception of the IPC communication channel\nthat is established between the two. Each process has its own memory, with\ntheir own V8 instances. Because of the additional resource allocations\nrequired, spawning a large number of child Node.js processes is not\nrecommended.
\nBy default, child_process.fork() will spawn new Node.js instances using the\nprocess.execPath of the parent process. The execPath property in the\noptions object allows for an alternative execution path to be used.
Node.js processes launched with a custom execPath will communicate with the\nparent process using the file descriptor (fd) identified using the\nenvironment variable NODE_CHANNEL_FD on the child process.
Unlike the fork(2) POSIX system call, child_process.fork() does not clone the\ncurrent process.
The shell option available in child_process.spawn() is not supported by\nchild_process.fork() and will be ignored if set.
The child_process.spawn() method spawns a new process using the given\ncommand, with command line arguments in args. If omitted, args defaults\nto an empty array.
If the shell option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
A third argument may be used to specify additional options, with these defaults:
\nconst defaults = {\n cwd: undefined,\n env: process.env\n};\nUse cwd to specify the working directory from which the process is spawned.\nIf not given, the default is to inherit the current working directory.
Use env to specify environment variables that will be visible to the new\nprocess, the default is process.env.
undefined values in env will be ignored.
Example of running ls -lh /usr, capturing stdout, stderr, and the\nexit code:
const { spawn } = require('child_process');\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.log(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});\nExample: A very elaborate way to run ps ax | grep ssh
const { spawn } = require('child_process');\nconst ps = spawn('ps', ['ax']);\nconst grep = spawn('grep', ['ssh']);\n\nps.stdout.on('data', (data) => {\n grep.stdin.write(data);\n});\n\nps.stderr.on('data', (data) => {\n console.log(`ps stderr: ${data}`);\n});\n\nps.on('close', (code) => {\n if (code !== 0) {\n console.log(`ps process exited with code ${code}`);\n }\n grep.stdin.end();\n});\n\ngrep.stdout.on('data', (data) => {\n console.log(data.toString());\n});\n\ngrep.stderr.on('data', (data) => {\n console.log(`grep stderr: ${data}`);\n});\n\ngrep.on('close', (code) => {\n if (code !== 0) {\n console.log(`grep process exited with code ${code}`);\n }\n});\nExample of checking for failed spawn:
const { spawn } = require('child_process');\nconst subprocess = spawn('bad_command');\n\nsubprocess.on('error', (err) => {\n console.log('Failed to start subprocess.');\n});\nCertain platforms (macOS, Linux) will use the value of argv[0] for the process\ntitle while others (Windows, SunOS) will use command.
Node.js currently overwrites argv[0] with process.execPath on startup, so\nprocess.argv[0] in a Node.js child process will not match the argv0\nparameter passed to spawn from the parent, retrieve it with the\nprocess.argv0 property instead.
On Windows, setting options.detached to true makes it possible for the\nchild process to continue running after the parent exits. The child will have\nits own console window. Once enabled for a child process, it cannot be\ndisabled.
On non-Windows platforms, if options.detached is set to true, the child\nprocess will be made the leader of a new process group and session. Note that\nchild processes may continue running after the parent exits regardless of\nwhether they are detached or not. See setsid(2) for more information.
By default, the parent will wait for the detached child to exit. To prevent the\nparent from waiting for a given subprocess to exit, use the\nsubprocess.unref() method. Doing so will cause the parent's event loop to not\ninclude the child in its reference count, allowing the parent to exit\nindependently of the child, unless there is an established IPC channel between\nthe child and the parent.
When using the detached option to start a long-running process, the process\nwill not stay running in the background after the parent exits unless it is\nprovided with a stdio configuration that is not connected to the parent.\nIf the parent's stdio is inherited, the child will remain attached to the\ncontrolling terminal.
Example of a long-running process, by detaching and also ignoring its parent\nstdio file descriptors, in order to ignore the parent's termination:
const { spawn } = require('child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore'\n});\n\nsubprocess.unref();\nAlternatively one can redirect the child process' output into files:
\nconst fs = require('fs');\nconst { spawn } = require('child_process');\nconst out = fs.openSync('./out.log', 'a');\nconst err = fs.openSync('./out.log', 'a');\n\nconst subprocess = spawn('prg', [], {\n detached: true,\n stdio: [ 'ignore', out, err ]\n});\n\nsubprocess.unref();\nThe options.stdio option is used to configure the pipes that are established\nbetween the parent and child process. By default, the child's stdin, stdout,\nand stderr are redirected to corresponding subprocess.stdin,\nsubprocess.stdout, and subprocess.stderr streams on the\nChildProcess object. This is equivalent to setting the options.stdio\nequal to ['pipe', 'pipe', 'pipe'].
For convenience, options.stdio may be one of the following strings:
'pipe' - equivalent to ['pipe', 'pipe', 'pipe'] (the default)'ignore' - equivalent to ['ignore', 'ignore', 'ignore']'inherit' - equivalent to ['inherit', 'inherit', 'inherit'] or [0, 1, 2]Otherwise, the value of options.stdio is an array where each index corresponds\nto an fd in the child. The fds 0, 1, and 2 correspond to stdin, stdout,\nand stderr, respectively. Additional fds can be specified to create additional\npipes between the parent and child. The value is one of the following:
'pipe' - Create a pipe between the child process and the parent process.\nThe parent end of the pipe is exposed to the parent as a property on the\nchild_process object as subprocess.stdio[fd]. Pipes created\nfor fds 0 - 2 are also available as subprocess.stdin,\nsubprocess.stdout and subprocess.stderr, respectively.
'ipc' - Create an IPC channel for passing messages/file descriptors\nbetween parent and child. A ChildProcess may have at most one IPC stdio\nfile descriptor. Setting this option enables the subprocess.send()\nmethod. If the child is a Node.js process, the presence of an IPC channel\nwill enable process.send() and process.disconnect() methods,\nas well as 'disconnect' and 'message' events within the child.
Accessing the IPC channel fd in any way other than process.send()\nor using the IPC channel with a child process that is not a Node.js instance\nis not supported.
'ignore' - Instructs Node.js to ignore the fd in the child. While Node.js\nwill always open fds 0 - 2 for the processes it spawns, setting the fd to\n'ignore' will cause Node.js to open /dev/null and attach it to the\nchild's fd.
'inherit' - Pass through the corresponding stdio stream to/from the\nparent process. In the first three positions, this is equivalent to\nprocess.stdin, process.stdout, and process.stderr, respectively. In\nany other position, equivalent to 'ignore'.
<Stream> object - Share a readable or writable stream that refers to a tty,\nfile, socket, or a pipe with the child process. The stream's underlying\nfile descriptor is duplicated in the child process to the fd that\ncorresponds to the index in the stdio array. Note that the stream must\nhave an underlying descriptor (file streams do not until the 'open'\nevent has occurred).
Positive integer - The integer value is interpreted as a file descriptor\nthat is currently open in the parent process. It is shared with the child\nprocess, similar to how <Stream> objects can be shared. Passing sockets\nis not supported on Windows.
\nnull, undefined - Use default value. For stdio fds 0, 1, and 2 (in other\nwords, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the\ndefault is 'ignore'.
const { spawn } = require('child_process');\n\n// Child will use parent's stdios\nspawn('prg', [], { stdio: 'inherit' });\n\n// Spawn child sharing only stderr\nspawn('prg', [], { stdio: ['pipe', 'pipe', process.stderr] });\n\n// Open an extra fd=4, to interact with programs presenting a\n// startd-style interface.\nspawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });\nIt is worth noting that when an IPC channel is established between the\nparent and child processes, and the child is a Node.js process, the child\nis launched with the IPC channel unreferenced (using unref()) until the\nchild registers an event handler for the 'disconnect' event\nor the 'message' event. This allows the child to exit\nnormally without the process being held open by the open IPC channel.
On UNIX-like operating systems, the child_process.spawn() method\nperforms memory operations synchronously before decoupling the event loop\nfrom the child. Applications with a large memory footprint may find frequent\nchild_process.spawn() calls to be a bottleneck. For more information,\nsee V8 issue 7381.
See also: child_process.exec() and child_process.fork().
The child_process.spawnSync(), child_process.execSync(), and\nchild_process.execFileSync() methods are synchronous and WILL block\nthe Node.js event loop, pausing execution of any additional code until the\nspawned process exits.
Blocking calls like these are mostly useful for simplifying general-purpose\nscripting tasks and for simplifying the loading/processing of application\nconfiguration at startup.
", "methods": [ { "textRaw": "child_process.execFileSync(file[, args][, options])", "type": "method", "name": "execFileSync", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/22409", "description": "The `input` option can now be any `TypedArray` or a `DataView`." }, { "version": "v8.8.0", "pr-url": "https://github.com/nodejs/node/pull/15380", "description": "The `windowsHide` option is supported now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/10653", "description": "The `input` option can now be a `Uint8Array`." }, { "version": "v6.2.1, v4.5.0", "pr-url": "https://github.com/nodejs/node/pull/6939", "description": "The `encoding` option can now explicitly be set to `buffer`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer|string} The stdout from the command.", "name": "return", "type": "Buffer|string", "desc": "The stdout from the command." }, "params": [ { "textRaw": "`file` {string} The name or path of the executable file to run.", "name": "file", "type": "string", "desc": "The name or path of the executable file to run." }, { "textRaw": "`args` {string[]} List of string arguments.", "name": "args", "type": "string[]", "desc": "List of string arguments.", "optional": true }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string} Current working directory of the child process.", "name": "cwd", "type": "string", "desc": "Current working directory of the child process." }, { "textRaw": "`input` {string|Buffer|TypedArray|DataView} The value which will be passed as stdin to the spawned process. Supplying this value will override `stdio[0]`.", "name": "input", "type": "string|Buffer|TypedArray|DataView", "desc": "The value which will be passed as stdin to the spawned process. Supplying this value will override `stdio[0]`." }, { "textRaw": "`stdio` {string|Array} Child's stdio configuration. `stderr` by default will be output to the parent process' stderr unless `stdio` is specified. **Default:** `'pipe'`.", "name": "stdio", "type": "string|Array", "default": "`'pipe'`", "desc": "Child's stdio configuration. `stderr` by default will be output to the parent process' stderr unless `stdio` is specified." }, { "textRaw": "`env` {Object} Environment key-value pairs.", "name": "env", "type": "Object", "desc": "Environment key-value pairs." }, { "textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).", "name": "uid", "type": "number", "desc": "Sets the user identity of the process (see setuid(2))." }, { "textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).", "name": "gid", "type": "number", "desc": "Sets the group identity of the process (see setgid(2))." }, { "textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.", "name": "timeout", "type": "number", "default": "`undefined`", "desc": "In milliseconds the maximum amount of time the process is allowed to run." }, { "textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed. **Default:** `'SIGTERM'`.", "name": "killSignal", "type": "string|integer", "default": "`'SIGTERM'`", "desc": "The signal value to be used when the spawned process will be killed." }, { "textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`200 * 1024`", "desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated. See caveat at [`maxBuffer` and Unicode][]." }, { "textRaw": "`encoding` {string} The encoding used for all stdio inputs and outputs. **Default:** `'buffer'`.", "name": "encoding", "type": "string", "default": "`'buffer'`", "desc": "The encoding used for all stdio inputs and outputs." }, { "textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.", "name": "windowsHide", "type": "boolean", "default": "`false`", "desc": "Hide the subprocess console window that would normally be created on Windows systems." }, { "textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on UNIX, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell Requirements][] and [Default Windows Shell][]. **Default:** `false` (no shell).", "name": "shell", "type": "boolean|string", "default": "`false` (no shell)", "desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on UNIX, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell Requirements][] and [Default Windows Shell][]." } ], "optional": true } ] } ], "desc": "The child_process.execFileSync() method is generally identical to\nchild_process.execFile() with the exception that the method will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal is sent, the method won't return until the process has\ncompletely exited.
If the child process intercepts and handles the SIGTERM signal and\ndoes not exit, the parent process will still wait until the child process has\nexited.
If the process times out or has a non-zero exit code, this method will\nthrow an Error that will include the full result of the underlying\nchild_process.spawnSync().
If the shell option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
The child_process.execSync() method is generally identical to\nchild_process.exec() with the exception that the method will not return until\nthe child process has fully closed. When a timeout has been encountered and\nkillSignal is sent, the method won't return until the process has completely\nexited. Note that if the child process intercepts and handles the SIGTERM\nsignal and doesn't exit, the parent process will wait until the child\nprocess has exited.
If the process times out or has a non-zero exit code, this method will\nthrow. The Error object will contain the entire result from\nchild_process.spawnSync().
Never pass unsanitized user input to this function. Any input containing shell\nmetacharacters may be used to trigger arbitrary command execution.
" }, { "textRaw": "child_process.spawnSync(command[, args][, options])", "type": "method", "name": "spawnSync", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": "v10.10.0", "pr-url": "https://github.com/nodejs/node/pull/22409", "description": "The `input` option can now be any `TypedArray` or a `DataView`." }, { "version": "v8.8.0", "pr-url": "https://github.com/nodejs/node/pull/15380", "description": "The `windowsHide` option is supported now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/10653", "description": "The `input` option can now be a `Uint8Array`." }, { "version": "v6.2.1, v4.5.0", "pr-url": "https://github.com/nodejs/node/pull/6939", "description": "The `encoding` option can now explicitly be set to `buffer`." }, { "version": "v5.7.0", "pr-url": "https://github.com/nodejs/node/pull/4598", "description": "The `shell` option is supported now." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object", "options": [ { "textRaw": "`pid` {number} Pid of the child process.", "name": "pid", "type": "number", "desc": "Pid of the child process." }, { "textRaw": "`output` {Array} Array of results from stdio output.", "name": "output", "type": "Array", "desc": "Array of results from stdio output." }, { "textRaw": "`stdout` {Buffer|string} The contents of `output[1]`.", "name": "stdout", "type": "Buffer|string", "desc": "The contents of `output[1]`." }, { "textRaw": "`stderr` {Buffer|string} The contents of `output[2]`.", "name": "stderr", "type": "Buffer|string", "desc": "The contents of `output[2]`." }, { "textRaw": "`status` {number|null} The exit code of the subprocess, or `null` if the subprocess terminated due to a signal.", "name": "status", "type": "number|null", "desc": "The exit code of the subprocess, or `null` if the subprocess terminated due to a signal." }, { "textRaw": "`signal` {string|null} The signal used to kill the subprocess, or `null` if the subprocess did not terminate due to a signal.", "name": "signal", "type": "string|null", "desc": "The signal used to kill the subprocess, or `null` if the subprocess did not terminate due to a signal." }, { "textRaw": "`error` {Error} The error object if the child process failed or timed out.", "name": "error", "type": "Error", "desc": "The error object if the child process failed or timed out." } ] }, "params": [ { "textRaw": "`command` {string} The command to run.", "name": "command", "type": "string", "desc": "The command to run." }, { "textRaw": "`args` {string[]} List of string arguments.", "name": "args", "type": "string[]", "desc": "List of string arguments.", "optional": true }, { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`cwd` {string} Current working directory of the child process.", "name": "cwd", "type": "string", "desc": "Current working directory of the child process." }, { "textRaw": "`input` {string|Buffer|TypedArray|DataView} The value which will be passed as stdin to the spawned process. Supplying this value will override `stdio[0]`.", "name": "input", "type": "string|Buffer|TypedArray|DataView", "desc": "The value which will be passed as stdin to the spawned process. Supplying this value will override `stdio[0]`." }, { "textRaw": "`argv0` {string} Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified.", "name": "argv0", "type": "string", "desc": "Explicitly set the value of `argv[0]` sent to the child process. This will be set to `command` if not specified." }, { "textRaw": "`stdio` {string|Array} Child's stdio configuration.", "name": "stdio", "type": "string|Array", "desc": "Child's stdio configuration." }, { "textRaw": "`env` {Object} Environment key-value pairs.", "name": "env", "type": "Object", "desc": "Environment key-value pairs." }, { "textRaw": "`uid` {number} Sets the user identity of the process (see setuid(2)).", "name": "uid", "type": "number", "desc": "Sets the user identity of the process (see setuid(2))." }, { "textRaw": "`gid` {number} Sets the group identity of the process (see setgid(2)).", "name": "gid", "type": "number", "desc": "Sets the group identity of the process (see setgid(2))." }, { "textRaw": "`timeout` {number} In milliseconds the maximum amount of time the process is allowed to run. **Default:** `undefined`.", "name": "timeout", "type": "number", "default": "`undefined`", "desc": "In milliseconds the maximum amount of time the process is allowed to run." }, { "textRaw": "`killSignal` {string|integer} The signal value to be used when the spawned process will be killed. **Default:** `'SIGTERM'`.", "name": "killSignal", "type": "string|integer", "default": "`'SIGTERM'`", "desc": "The signal value to be used when the spawned process will be killed." }, { "textRaw": "`maxBuffer` {number} Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]. **Default:** `200 * 1024`.", "name": "maxBuffer", "type": "number", "default": "`200 * 1024`", "desc": "Largest amount of data in bytes allowed on stdout or stderr. If exceeded, the child process is terminated and any output is truncated. See caveat at [`maxBuffer` and Unicode][]." }, { "textRaw": "`encoding` {string} The encoding used for all stdio inputs and outputs. **Default:** `'buffer'`.", "name": "encoding", "type": "string", "default": "`'buffer'`", "desc": "The encoding used for all stdio inputs and outputs." }, { "textRaw": "`shell` {boolean|string} If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on UNIX, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell Requirements][] and [Default Windows Shell][]. **Default:** `false` (no shell).", "name": "shell", "type": "boolean|string", "default": "`false` (no shell)", "desc": "If `true`, runs `command` inside of a shell. Uses `'/bin/sh'` on UNIX, and `process.env.ComSpec` on Windows. A different shell can be specified as a string. See [Shell Requirements][] and [Default Windows Shell][]." }, { "textRaw": "`windowsVerbatimArguments` {boolean} No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified. **Default:** `false`.", "name": "windowsVerbatimArguments", "type": "boolean", "default": "`false`", "desc": "No quoting or escaping of arguments is done on Windows. Ignored on Unix. This is set to `true` automatically when `shell` is specified." }, { "textRaw": "`windowsHide` {boolean} Hide the subprocess console window that would normally be created on Windows systems. **Default:** `false`.", "name": "windowsHide", "type": "boolean", "default": "`false`", "desc": "Hide the subprocess console window that would normally be created on Windows systems." } ], "optional": true } ] } ], "desc": "The child_process.spawnSync() method is generally identical to\nchild_process.spawn() with the exception that the function will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal is sent, the method won't return until the process has\ncompletely exited. Note that if the process intercepts and handles the\nSIGTERM signal and doesn't exit, the parent process will wait until the child\nprocess has exited.
If the shell option is enabled, do not pass unsanitized user input to this\nfunction. Any input containing shell metacharacters may be used to trigger\narbitrary command execution.
The maxBuffer option specifies the largest number of bytes allowed on stdout\nor stderr. If this value is exceeded, then the child process is terminated.\nThis impacts output that includes multibyte character encodings such as UTF-8 or\nUTF-16. For instance, console.log('中文测试') will send 13 UTF-8 encoded bytes\nto stdout although there are only 4 characters.
The shell should understand the -c switch on UNIX or /d /s /c on Windows.\nOn Windows, command line parsing should be compatible with 'cmd.exe'.
Although Microsoft specifies %COMSPEC% must contain the path to\n'cmd.exe' in the root environment, child processes are not always subject to\nthe same requirement. Thus, in child_process functions where a shell can be\nspawned, 'cmd.exe' is used as a fallback if process.env.ComSpec is\nunavailable.
Instances of the ChildProcess class are EventEmitters that represent\nspawned child processes.
Instances of ChildProcess are not intended to be created directly. Rather,\nuse the child_process.spawn(), child_process.exec(),\nchild_process.execFile(), or child_process.fork() methods to create\ninstances of ChildProcess.
The 'close' event is emitted when the stdio streams of a child process have\nbeen closed. This is distinct from the 'exit' event, since multiple\nprocesses might share the same stdio streams.
The 'disconnect' event is emitted after calling the\nsubprocess.disconnect() method in parent process or\nprocess.disconnect() in child process. After disconnecting it is no longer\npossible to send or receive messages, and the subprocess.connected\nproperty is false.
The 'error' event is emitted whenever:
The 'exit' event may or may not fire after an error has occurred. When\nlistening to both the 'exit' and 'error' events, it is important to guard\nagainst accidentally invoking handler functions multiple times.
See also subprocess.kill() and subprocess.send().
The 'exit' event is emitted after the child process ends. If the process\nexited, code is the final exit code of the process, otherwise null. If the\nprocess terminated due to receipt of a signal, signal is the string name of\nthe signal, otherwise null. One of the two will always be non-null.
Note that when the 'exit' event is triggered, child process stdio streams\nmight still be open.
Also, note that Node.js establishes signal handlers for SIGINT and\nSIGTERM and Node.js processes will not terminate immediately due to receipt\nof those signals. Rather, Node.js will perform a sequence of cleanup actions\nand then will re-raise the handled signal.
See waitpid(2).
The 'message' event is triggered when a child process uses process.send()\nto send messages.
The message goes through serialization and parsing. The resulting\nmessage might not be the same as what is originally sent.
" } ], "properties": [ { "textRaw": "`channel` {Object} A pipe representing the IPC channel to the child process.", "type": "Object", "name": "channel", "meta": { "added": [ "v7.1.0" ], "changes": [] }, "desc": "The subprocess.channel property is a reference to the child's IPC channel. If\nno IPC channel currently exists, this property is undefined.
The subprocess.connected property indicates whether it is still possible to\nsend and receive messages from a child process. When subprocess.connected is\nfalse, it is no longer possible to send or receive messages.
The subprocess.killed property indicates whether the child process\nsuccessfully received a signal from subprocess.kill(). The killed property\ndoes not indicate that the child process has been terminated.
Returns the process identifier (PID) of the child process.
\nconst { spawn } = require('child_process');\nconst grep = spawn('grep', ['ssh']);\n\nconsole.log(`Spawned child pid: ${grep.pid}`);\ngrep.stdin.end();\nA Readable Stream that represents the child process's stderr.
If the child was spawned with stdio[2] set to anything other than 'pipe',\nthen this will be null.
subprocess.stderr is an alias for subprocess.stdio[2]. Both properties will\nrefer to the same value.
A Writable Stream that represents the child process's stdin.
Note that if a child process waits to read all of its input, the child will not\ncontinue until this stream has been closed via end().
If the child was spawned with stdio[0] set to anything other than 'pipe',\nthen this will be null.
subprocess.stdin is an alias for subprocess.stdio[0]. Both properties will\nrefer to the same value.
A sparse array of pipes to the child process, corresponding with positions in\nthe stdio option passed to child_process.spawn() that have been set\nto the value 'pipe'. Note that subprocess.stdio[0], subprocess.stdio[1],\nand subprocess.stdio[2] are also available as subprocess.stdin,\nsubprocess.stdout, and subprocess.stderr, respectively.
In the following example, only the child's fd 1 (stdout) is configured as a\npipe, so only the parent's subprocess.stdio[1] is a stream, all other values\nin the array are null.
const assert = require('assert');\nconst fs = require('fs');\nconst child_process = require('child_process');\n\nconst subprocess = child_process.spawn('ls', {\n stdio: [\n 0, // Use parent's stdin for child\n 'pipe', // Pipe child's stdout to parent\n fs.openSync('err.out', 'w') // Direct child's stderr to a file\n ]\n});\n\nassert.strictEqual(subprocess.stdio[0], null);\nassert.strictEqual(subprocess.stdio[0], subprocess.stdin);\n\nassert(subprocess.stdout);\nassert.strictEqual(subprocess.stdio[1], subprocess.stdout);\n\nassert.strictEqual(subprocess.stdio[2], null);\nassert.strictEqual(subprocess.stdio[2], subprocess.stderr);\nA Readable Stream that represents the child process's stdout.
If the child was spawned with stdio[1] set to anything other than 'pipe',\nthen this will be null.
subprocess.stdout is an alias for subprocess.stdio[1]. Both properties will\nrefer to the same value.
Closes the IPC channel between parent and child, allowing the child to exit\ngracefully once there are no other connections keeping it alive. After calling\nthis method the subprocess.connected and process.connected properties in\nboth the parent and child (respectively) will be set to false, and it will be\nno longer possible to pass messages between the processes.
The 'disconnect' event will be emitted when there are no messages in the\nprocess of being received. This will most often be triggered immediately after\ncalling subprocess.disconnect().
Note that when the child process is a Node.js instance (e.g. spawned using\nchild_process.fork()), the process.disconnect() method can be invoked\nwithin the child process to close the IPC channel as well.
The subprocess.kill() method sends a signal to the child process. If no\nargument is given, the process will be sent the 'SIGTERM' signal. See\nsignal(7) for a list of available signals.
const { spawn } = require('child_process');\nconst grep = spawn('grep', ['ssh']);\n\ngrep.on('close', (code, signal) => {\n console.log(\n `child process terminated due to receipt of signal ${signal}`);\n});\n\n// Send SIGHUP to process\ngrep.kill('SIGHUP');\nThe ChildProcess object may emit an 'error' event if the signal cannot be\ndelivered. Sending a signal to a child process that has already exited is not\nan error but may have unforeseen consequences. Specifically, if the process\nidentifier (PID) has been reassigned to another process, the signal will be\ndelivered to that process instead which can have unexpected results.
Note that while the function is called kill, the signal delivered to the\nchild process may not actually terminate the process.
See kill(2) for reference.
On Linux, child processes of child processes will not be terminated\nwhen attempting to kill their parent. This is likely to happen when running a\nnew process in a shell or with the use of the shell option of ChildProcess:
'use strict';\nconst { spawn } = require('child_process');\n\nconst subprocess = spawn(\n 'sh',\n [\n '-c',\n `node -e \"setInterval(() => {\n console.log(process.pid, 'is alive')\n }, 500);\"`\n ], {\n stdio: ['inherit', 'inherit', 'inherit']\n }\n);\n\nsetTimeout(() => {\n subprocess.kill(); // does not terminate the node process in the shell\n}, 2000);\nCalling subprocess.ref() after making a call to subprocess.unref() will\nrestore the removed reference count for the child process, forcing the parent\nto wait for the child to exit before exiting itself.
const { spawn } = require('child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore'\n});\n\nsubprocess.unref();\nsubprocess.ref();\nWhen an IPC channel has been established between the parent and child (\ni.e. when using child_process.fork()), the subprocess.send() method can\nbe used to send messages to the child process. When the child process is a\nNode.js instance, these messages can be received via the 'message' event.
The message goes through serialization and parsing. The resulting\nmessage might not be the same as what is originally sent.
\nFor example, in the parent script:
\nconst cp = require('child_process');\nconst n = cp.fork(`${__dirname}/sub.js`);\n\nn.on('message', (m) => {\n console.log('PARENT got message:', m);\n});\n\n// Causes the child to print: CHILD got message: { hello: 'world' }\nn.send({ hello: 'world' });\nAnd then the child script, 'sub.js' might look like this:
process.on('message', (m) => {\n console.log('CHILD got message:', m);\n});\n\n// Causes the parent to print: PARENT got message: { foo: 'bar', baz: null }\nprocess.send({ foo: 'bar', baz: NaN });\nChild Node.js processes will have a process.send() method of their own that\nallows the child to send messages back to the parent.
There is a special case when sending a {cmd: 'NODE_foo'} message. Messages\ncontaining a NODE_ prefix in the cmd property are reserved for use within\nNode.js core and will not be emitted in the child's 'message'\nevent. Rather, such messages are emitted using the\n'internalMessage' event and are consumed internally by Node.js.\nApplications should avoid using such messages or listening for\n'internalMessage' events as it is subject to change without notice.
The optional sendHandle argument that may be passed to subprocess.send() is\nfor passing a TCP server or socket object to the child process. The child will\nreceive the object as the second argument passed to the callback function\nregistered on the 'message' event. Any data that is received\nand buffered in the socket will not be sent to the child.
The optional callback is a function that is invoked after the message is\nsent but before the child may have received it. The function is called with a\nsingle argument: null on success, or an Error object on failure.
If no callback function is provided and the message cannot be sent, an\n'error' event will be emitted by the ChildProcess object. This can happen,\nfor instance, when the child process has already exited.
subprocess.send() will return false if the channel has closed or when the\nbacklog of unsent messages exceeds a threshold that makes it unwise to send\nmore. Otherwise, the method returns true. The callback function can be\nused to implement flow control.
The sendHandle argument can be used, for instance, to pass the handle of\na TCP server object to the child process as illustrated in the example below:
const subprocess = require('child_process').fork('subprocess.js');\n\n// Open up the server object and send the handle.\nconst server = require('net').createServer();\nserver.on('connection', (socket) => {\n socket.end('handled by parent');\n});\nserver.listen(1337, () => {\n subprocess.send('server', server);\n});\nThe child would then receive the server object as:
\nprocess.on('message', (m, server) => {\n if (m === 'server') {\n server.on('connection', (socket) => {\n socket.end('handled by child');\n });\n }\n});\nOnce the server is now shared between the parent and child, some connections\ncan be handled by the parent and some by the child.
\nWhile the example above uses a server created using the net module, dgram\nmodule servers use exactly the same workflow with the exceptions of listening on\na 'message' event instead of 'connection' and using server.bind() instead of\nserver.listen(). This is, however, currently only supported on UNIX platforms.
Similarly, the sendHandler argument can be used to pass the handle of a\nsocket to the child process. The example below spawns two children that each\nhandle connections with \"normal\" or \"special\" priority:
const { fork } = require('child_process');\nconst normal = fork('subprocess.js', ['normal']);\nconst special = fork('subprocess.js', ['special']);\n\n// Open up the server and send sockets to child. Use pauseOnConnect to prevent\n// the sockets from being read before they are sent to the child process.\nconst server = require('net').createServer({ pauseOnConnect: true });\nserver.on('connection', (socket) => {\n\n // If this is special priority\n if (socket.remoteAddress === '74.125.127.100') {\n special.send('socket', socket);\n return;\n }\n // This is normal priority\n normal.send('socket', socket);\n});\nserver.listen(1337);\nThe subprocess.js would receive the socket handle as the second argument\npassed to the event callback function:
process.on('message', (m, socket) => {\n if (m === 'socket') {\n if (socket) {\n // Check that the client socket exists.\n // It is possible for the socket to be closed between the time it is\n // sent and the time it is received in the child process.\n socket.end(`Request handled with ${process.argv[2]} priority`);\n }\n }\n});\nOnce a socket has been passed to a child, the parent is no longer capable of\ntracking when the socket is destroyed. To indicate this, the .connections\nproperty becomes null. It is recommended not to use .maxConnections when\nthis occurs.
It is also recommended that any 'message' handlers in the child process\nverify that socket exists, as the connection may have been closed during the\ntime it takes to send the connection to the child.
By default, the parent will wait for the detached child to exit. To prevent the\nparent from waiting for a given subprocess to exit, use the\nsubprocess.unref() method. Doing so will cause the parent's event loop to not\ninclude the child in its reference count, allowing the parent to exit\nindependently of the child, unless there is an established IPC channel between\nthe child and the parent.
const { spawn } = require('child_process');\n\nconst subprocess = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: 'ignore'\n});\n\nsubprocess.unref();\nA single instance of Node.js runs in a single thread. To take advantage of\nmulti-core systems, the user will sometimes want to launch a cluster of Node.js\nprocesses to handle the load.
\nThe cluster module allows easy creation of child processes that all share\nserver ports.
\nconst cluster = require('cluster');\nconst http = require('http');\nconst numCPUs = require('os').cpus().length;\n\nif (cluster.isMaster) {\n console.log(`Master ${process.pid} is running`);\n\n // Fork workers.\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('exit', (worker, code, signal) => {\n console.log(`worker ${worker.process.pid} died`);\n });\n} else {\n // Workers can share any TCP connection\n // In this case it is an HTTP server\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n }).listen(8000);\n\n console.log(`Worker ${process.pid} started`);\n}\nRunning Node.js will now share port 8000 between the workers:
\n$ node server.js\nMaster 3596 is running\nWorker 4324 started\nWorker 4520 started\nWorker 6056 started\nWorker 5644 started\nPlease note that on Windows, it is not yet possible to set up a named pipe\nserver in a worker.
", "miscs": [ { "textRaw": "How It Works", "name": "How It Works", "type": "misc", "desc": "The worker processes are spawned using the child_process.fork() method,\nso that they can communicate with the parent via IPC and pass server\nhandles back and forth.
The cluster module supports two methods of distributing incoming\nconnections.
\nThe first one (and the default one on all platforms except Windows),\nis the round-robin approach, where the master process listens on a\nport, accepts new connections and distributes them across the workers\nin a round-robin fashion, with some built-in smarts to avoid\noverloading a worker process.
\nThe second approach is where the master process creates the listen\nsocket and sends it to interested workers. The workers then accept\nincoming connections directly.
\nThe second approach should, in theory, give the best performance.\nIn practice however, distribution tends to be very unbalanced due\nto operating system scheduler vagaries. Loads have been observed\nwhere over 70% of all connections ended up in just two processes,\nout of a total of eight.
\nBecause server.listen() hands off most of the work to the master\nprocess, there are three cases where the behavior between a normal\nNode.js process and a cluster worker differs:
server.listen({fd: 7}) Because the message is passed to the master,\nfile descriptor 7 in the parent will be listened on, and the\nhandle passed to the worker, rather than listening to the worker's\nidea of what the number 7 file descriptor references.server.listen(handle) Listening on handles explicitly will cause\nthe worker to use the supplied handle, rather than talk to the master\nprocess.server.listen(0) Normally, this will cause servers to listen on a\nrandom port. However, in a cluster, each worker will receive the\nsame \"random\" port each time they do listen(0). In essence, the\nport is random the first time, but predictable thereafter. To listen\non a unique port, generate a port number based on the cluster worker ID.Node.js does not provide routing logic. It is, therefore important to design an\napplication such that it does not rely too heavily on in-memory data objects for\nthings like sessions and login.
\nBecause workers are all separate processes, they can be killed or\nre-spawned depending on a program's needs, without affecting other\nworkers. As long as there are some workers still alive, the server will\ncontinue to accept connections. If no workers are alive, existing connections\nwill be dropped and new connections will be refused. Node.js does not\nautomatically manage the number of workers, however. It is the application's\nresponsibility to manage the worker pool based on its own needs.
\nAlthough a primary use case for the cluster module is networking, it can\nalso be used for other use cases requiring worker processes.
A Worker object contains all public information and method about a worker.\nIn the master it can be obtained using cluster.workers. In a worker\nit can be obtained using cluster.worker.
Similar to the cluster.on('disconnect') event, but specific to this worker.
cluster.fork().on('disconnect', () => {\n // Worker has disconnected\n});\nThis event is the same as the one provided by child_process.fork().
Within a worker, process.on('error') may also be used.
Similar to the cluster.on('exit') event, but specific to this worker.
const worker = cluster.fork();\nworker.on('exit', (code, signal) => {\n if (signal) {\n console.log(`worker was killed by signal: ${signal}`);\n } else if (code !== 0) {\n console.log(`worker exited with error code: ${code}`);\n } else {\n console.log('worker success!');\n }\n});\nSimilar to the cluster.on('listening') event, but specific to this worker.
cluster.fork().on('listening', (address) => {\n // Worker is listening\n});\nIt is not emitted in the worker.
" }, { "textRaw": "Event: 'message'", "type": "event", "name": "message", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "params": [ { "textRaw": "`message` {Object}", "name": "message", "type": "Object" }, { "textRaw": "`handle` {undefined|Object}", "name": "handle", "type": "undefined|Object" } ], "desc": "Similar to the 'message' event of cluster, but specific to this worker.
Within a worker, process.on('message') may also be used.
Here is an example using the message system. It keeps a count in the master\nprocess of the number of HTTP requests received by the workers:
\nconst cluster = require('cluster');\nconst http = require('http');\n\nif (cluster.isMaster) {\n\n // Keep track of http requests\n let numReqs = 0;\n setInterval(() => {\n console.log(`numReqs = ${numReqs}`);\n }, 1000);\n\n // Count requests\n function messageHandler(msg) {\n if (msg.cmd && msg.cmd === 'notifyRequest') {\n numReqs += 1;\n }\n }\n\n // Start workers and listen for messages containing notifyRequest\n const numCPUs = require('os').cpus().length;\n for (let i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n for (const id in cluster.workers) {\n cluster.workers[id].on('message', messageHandler);\n }\n\n} else {\n\n // Worker processes have a http server.\n http.Server((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n\n // notify master about the request\n process.send({ cmd: 'notifyRequest' });\n }).listen(8000);\n}\nSimilar to the cluster.on('online') event, but specific to this worker.
cluster.fork().on('online', () => {\n // Worker is online\n});\nIt is not emitted in the worker.
" } ], "methods": [ { "textRaw": "worker.disconnect()", "type": "method", "name": "disconnect", "meta": { "added": [ "v0.7.7" ], "changes": [ { "version": "v7.3.0", "pr-url": "https://github.com/nodejs/node/pull/10019", "description": "This method now returns a reference to `worker`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {cluster.Worker} A reference to `worker`.", "name": "return", "type": "cluster.Worker", "desc": "A reference to `worker`." }, "params": [] } ], "desc": "In a worker, this function will close all servers, wait for the 'close' event\non those servers, and then disconnect the IPC channel.
In the master, an internal message is sent to the worker causing it to call\n.disconnect() on itself.
Causes .exitedAfterDisconnect to be set.
Note that after a server is closed, it will no longer accept new connections,\nbut connections may be accepted by any other listening worker. Existing\nconnections will be allowed to close as usual. When no more connections exist,\nsee server.close(), the IPC channel to the worker will close allowing it\nto die gracefully.
The above applies only to server connections, client connections are not\nautomatically closed by workers, and disconnect does not wait for them to close\nbefore exiting.
\nNote that in a worker, process.disconnect exists, but it is not this function,\nit is disconnect.
Because long living server connections may block workers from disconnecting, it\nmay be useful to send a message, so application specific actions may be taken to\nclose them. It also may be useful to implement a timeout, killing a worker if\nthe 'disconnect' event has not been emitted after some time.
if (cluster.isMaster) {\n const worker = cluster.fork();\n let timeout;\n\n worker.on('listening', (address) => {\n worker.send('shutdown');\n worker.disconnect();\n timeout = setTimeout(() => {\n worker.kill();\n }, 2000);\n });\n\n worker.on('disconnect', () => {\n clearTimeout(timeout);\n });\n\n} else if (cluster.isWorker) {\n const net = require('net');\n const server = net.createServer((socket) => {\n // connections never end\n });\n\n server.listen(8000);\n\n process.on('message', (msg) => {\n if (msg === 'shutdown') {\n // initiate graceful close of any connections to server\n }\n });\n}\nThis function returns true if the worker is connected to its master via its\nIPC channel, false otherwise. A worker is connected to its master after it\nhas been created. It is disconnected after the 'disconnect' event is emitted.
This function returns true if the worker's process has terminated (either\nbecause of exiting or being signaled). Otherwise, it returns false.
This function will kill the worker. In the master, it does this by disconnecting\nthe worker.process, and once disconnected, killing with signal. In the\nworker, it does it by disconnecting the channel, and then exiting with code 0.
Because kill() attempts to gracefully disconnect the worker process, it is\nsusceptible to waiting indefinitely for the disconnect to complete. For example,\nif the worker enters an infinite loop, a graceful disconnect will never occur.\nIf the graceful disconnect behavior is not needed, use worker.process.kill().
Causes .exitedAfterDisconnect to be set.
This method is aliased as worker.destroy() for backwards compatibility.
Note that in a worker, process.kill() exists, but it is not this function,\nit is kill.
Send a message to a worker or master, optionally with a handle.
\nIn the master this sends a message to a specific worker. It is identical to\nChildProcess.send().
In a worker this sends a message to the master. It is identical to\nprocess.send().
This example will echo back all messages from the master:
\nif (cluster.isMaster) {\n const worker = cluster.fork();\n worker.send('hi there');\n\n} else if (cluster.isWorker) {\n process.on('message', (msg) => {\n process.send(msg);\n });\n}\nSet by calling .kill() or .disconnect(). Until then, it is undefined.
The boolean worker.exitedAfterDisconnect allows distinguishing between\nvoluntary and accidental exit, the master may choose not to respawn a worker\nbased on this value.
cluster.on('exit', (worker, code, signal) => {\n if (worker.exitedAfterDisconnect === true) {\n console.log('Oh, it was just voluntary – no need to worry');\n }\n});\n\n// kill worker\nworker.kill();\nEach new worker is given its own unique id, this id is stored in the\nid.
While a worker is alive, this is the key that indexes it in\ncluster.workers.
All workers are created using child_process.fork(), the returned object\nfrom this function is stored as .process. In a worker, the global process\nis stored.
See: Child Process module.
\nNote that workers will call process.exit(0) if the 'disconnect' event occurs\non process and .exitedAfterDisconnect is not true. This protects against\naccidental disconnection.
Emitted after the worker IPC channel has disconnected. This can occur when a\nworker exits gracefully, is killed, or is disconnected manually (such as with\nworker.disconnect()).
There may be a delay between the 'disconnect' and 'exit' events. These\nevents can be used to detect if the process is stuck in a cleanup or if there\nare long-living connections.
cluster.on('disconnect', (worker) => {\n console.log(`The worker #${worker.id} has disconnected`);\n});\nWhen any of the workers die the cluster module will emit the 'exit' event.
This can be used to restart the worker by calling .fork() again.
cluster.on('exit', (worker, code, signal) => {\n console.log('worker %d died (%s). restarting...',\n worker.process.pid, signal || code);\n cluster.fork();\n});\nSee child_process event: 'exit'.
When a new worker is forked the cluster module will emit a 'fork' event.\nThis can be used to log worker activity, and create a custom timeout.
const timeouts = [];\nfunction errorMsg() {\n console.error('Something must be wrong with the connection ...');\n}\n\ncluster.on('fork', (worker) => {\n timeouts[worker.id] = setTimeout(errorMsg, 2000);\n});\ncluster.on('listening', (worker, address) => {\n clearTimeout(timeouts[worker.id]);\n});\ncluster.on('exit', (worker, code, signal) => {\n clearTimeout(timeouts[worker.id]);\n errorMsg();\n});\nAfter calling listen() from a worker, when the 'listening' event is emitted\non the server a 'listening' event will also be emitted on cluster in the\nmaster.
The event handler is executed with two arguments, the worker contains the\nworker object and the address object contains the following connection\nproperties: address, port and addressType. This is very useful if the\nworker is listening on more than one address.
cluster.on('listening', (worker, address) => {\n console.log(\n `A worker is now connected to ${address.address}:${address.port}`);\n});\nThe addressType is one of:
4 (TCPv4)6 (TCPv6)-1 (unix domain socket)'udp4' or 'udp6' (UDP v4 or v6)Emitted when the cluster master receives a message from any worker.
\nSee child_process event: 'message'.
Before Node.js v6.0, this event emitted only the message and the handle,\nbut not the worker object, contrary to what the documentation stated.
\nIf support for older versions is required but a worker object is not\nrequired, it is possible to work around the discrepancy by checking the\nnumber of arguments:
\ncluster.on('message', (worker, message, handle) => {\n if (arguments.length === 2) {\n handle = message;\n message = worker;\n worker = undefined;\n }\n // ...\n});\nAfter forking a new worker, the worker should respond with an online message.\nWhen the master receives an online message it will emit this event.\nThe difference between 'fork' and 'online' is that fork is emitted when the\nmaster forks a worker, and 'online' is emitted when the worker is running.
cluster.on('online', (worker) => {\n console.log('Yay, the worker responded after it was forked');\n});\nEmitted every time .setupMaster() is called.
The settings object is the cluster.settings object at the time\n.setupMaster() was called and is advisory only, since multiple calls to\n.setupMaster() can be made in a single tick.
If accuracy is important, use cluster.settings.
Calls .disconnect() on each worker in cluster.workers.
When they are disconnected all internal handles will be closed, allowing the\nmaster process to die gracefully if no other event is waiting.
\nThe method takes an optional callback argument which will be called when\nfinished.
\nThis can only be called from the master process.
" }, { "textRaw": "cluster.fork([env])", "type": "method", "name": "fork", "meta": { "added": [ "v0.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {cluster.Worker}", "name": "return", "type": "cluster.Worker" }, "params": [ { "textRaw": "`env` {Object} Key/value pairs to add to worker process environment.", "name": "env", "type": "Object", "desc": "Key/value pairs to add to worker process environment.", "optional": true } ] } ], "desc": "Spawn a new worker process.
\nThis can only be called from the master process.
" }, { "textRaw": "cluster.setupMaster([settings])", "type": "method", "name": "setupMaster", "meta": { "added": [ "v0.7.1" ], "changes": [ { "version": "v6.4.0", "pr-url": "https://github.com/nodejs/node/pull/7838", "description": "The `stdio` option is supported now." } ] }, "signatures": [ { "params": [ { "textRaw": "`settings` {Object} See [`cluster.settings`][].", "name": "settings", "type": "Object", "desc": "See [`cluster.settings`][].", "optional": true } ] } ], "desc": "setupMaster is used to change the default 'fork' behavior. Once called,\nthe settings will be present in cluster.settings.
Note that:
\n.fork() and have no\neffect on workers that are already running..setupMaster() is\nthe env passed to .fork().cluster.setupMaster() is called.const cluster = require('cluster');\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'https'],\n silent: true\n});\ncluster.fork(); // https worker\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'http']\n});\ncluster.fork(); // http worker\nThis can only be called from the master process.
" } ], "properties": [ { "textRaw": "`isMaster` {boolean}", "type": "boolean", "name": "isMaster", "meta": { "added": [ "v0.8.1" ], "changes": [] }, "desc": "True if the process is a master. This is determined\nby the process.env.NODE_UNIQUE_ID. If process.env.NODE_UNIQUE_ID is\nundefined, then isMaster is true.
True if the process is not a master (it is the negation of cluster.isMaster).
The scheduling policy, either cluster.SCHED_RR for round-robin or\ncluster.SCHED_NONE to leave it to the operating system. This is a\nglobal setting and effectively frozen once either the first worker is spawned,\nor cluster.setupMaster() is called, whichever comes first.
SCHED_RR is the default on all operating systems except Windows.\nWindows will change to SCHED_RR once libuv is able to effectively\ndistribute IOCP handles without incurring a large performance hit.
cluster.schedulingPolicy can also be set through the\nNODE_CLUSTER_SCHED_POLICY environment variable. Valid\nvalues are 'rr' and 'none'.
After calling .setupMaster() (or .fork()) this settings object will contain\nthe settings, including the default values.
This object is not intended to be changed or set manually.
" }, { "textRaw": "`worker` {Object}", "type": "Object", "name": "worker", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "desc": "A reference to the current worker object. Not available in the master process.
\nconst cluster = require('cluster');\n\nif (cluster.isMaster) {\n console.log('I am master');\n cluster.fork();\n cluster.fork();\n} else if (cluster.isWorker) {\n console.log(`I am worker #${cluster.worker.id}`);\n}\nA hash that stores the active worker objects, keyed by id field. Makes it\neasy to loop through all the workers. It is only available in the master\nprocess.
A worker is removed from cluster.workers after the worker has disconnected\nand exited. The order between these two events cannot be determined in\nadvance. However, it is guaranteed that the removal from the cluster.workers\nlist happens before last 'disconnect' or 'exit' event is emitted.
// Go through all workers\nfunction eachWorker(callback) {\n for (const id in cluster.workers) {\n callback(cluster.workers[id]);\n }\n}\neachWorker((worker) => {\n worker.send('big announcement to all workers');\n});\nUsing the worker's unique id is the easiest way to locate the worker.
\nsocket.on('data', (id) => {\n const worker = cluster.workers[id];\n});\nThe console module provides a simple debugging console that is similar to the\nJavaScript console mechanism provided by web browsers.
The module exports two specific components:
\nConsole class with methods such as console.log(), console.error() and\nconsole.warn() that can be used to write to any Node.js stream.console instance configured to write to process.stdout and\nprocess.stderr. The global console can be used without calling\nrequire('console').Warning: The global console object's methods are neither consistently\nsynchronous like the browser APIs they resemble, nor are they consistently\nasynchronous like all other Node.js streams. See the note on process I/O for\nmore information.
\nExample using the global console:
console.log('hello world');\n// Prints: hello world, to stdout\nconsole.log('hello %s', 'world');\n// Prints: hello world, to stdout\nconsole.error(new Error('Whoops, something bad happened'));\n// Prints: [Error: Whoops, something bad happened], to stderr\n\nconst name = 'Will Robinson';\nconsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to stderr\nExample using the Console class:
const out = getStreamSomehow();\nconst err = getStreamSomehow();\nconst myConsole = new console.Console(out, err);\n\nmyConsole.log('hello world');\n// Prints: hello world, to out\nmyConsole.log('hello %s', 'world');\n// Prints: hello world, to out\nmyConsole.error(new Error('Whoops, something bad happened'));\n// Prints: [Error: Whoops, something bad happened], to err\n\nconst name = 'Will Robinson';\nmyConsole.warn(`Danger ${name}! Danger!`);\n// Prints: Danger Will Robinson! Danger!, to err\nThe Console class can be used to create a simple logger with configurable\noutput streams and can be accessed using either require('console').Console\nor console.Console (or their destructured counterparts):
const { Console } = require('console');\nconst { Console } = console;\nA simple assertion test that verifies whether value is truthy. If it is not,\nAssertion failed is logged. If provided, the error message is formatted\nusing util.format() by passing along all message arguments. The output is\nused as the error message.
console.assert(true, 'does nothing');\n// OK\nconsole.assert(false, 'Whoops %s work', 'didn\\'t');\n// Assertion failed: Whoops didn't work\nCalling console.assert() with a falsy assertion will only cause the message\nto be printed to the console without interrupting execution of subsequent code.
When stdout is a TTY, calling console.clear() will attempt to clear the\nTTY. When stdout is not a TTY, this method does nothing.
The specific operation of console.clear() can vary across operating systems\nand terminal types. For most Linux operating systems, console.clear()\noperates similarly to the clear shell command. On Windows, console.clear()\nwill clear only the output in the current terminal viewport for the Node.js\nbinary.
Maintains an internal counter specific to label and outputs to stdout the\nnumber of times console.count() has been called with the given label.
> console.count()\ndefault: 1\nundefined\n> console.count('default')\ndefault: 2\nundefined\n> console.count('abc')\nabc: 1\nundefined\n> console.count('xyz')\nxyz: 1\nundefined\n> console.count('abc')\nabc: 2\nundefined\n> console.count()\ndefault: 3\nundefined\n>\nResets the internal counter specific to label.
> console.count('abc');\nabc: 1\nundefined\n> console.countReset('abc');\nundefined\n> console.count('abc');\nabc: 1\nundefined\n>\nThe console.debug() function is an alias for console.log().
Uses util.inspect() on obj and prints the resulting string to stdout.\nThis function bypasses any custom inspect() function defined on obj.
This method calls console.log() passing it the arguments received.\nPlease note that this method does not produce any XML formatting.
Prints to stderr with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3) (the arguments are all passed to\nutil.format()).
const code = 5;\nconsole.error('error #%d', code);\n// Prints: error #5, to stderr\nconsole.error('error', code);\n// Prints: error 5, to stderr\nIf formatting elements (e.g. %d) are not found in the first string then\nutil.inspect() is called on each argument and the resulting string\nvalues are concatenated. See util.format() for more information.
Increases indentation of subsequent lines by two spaces.
\nIf one or more labels are provided, those are printed first without the\nadditional indentation.
An alias for console.group().
Decreases indentation of subsequent lines by two spaces.
" }, { "textRaw": "console.info([data][, ...args])", "type": "method", "name": "info", "meta": { "added": [ "v0.1.100" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`data` {any}", "name": "data", "type": "any", "optional": true }, { "textRaw": "`...args` {any}", "name": "...args", "type": "any", "optional": true } ] } ], "desc": "The console.info() function is an alias for console.log().
Prints to stdout with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3) (the arguments are all passed to\nutil.format()).
const count = 5;\nconsole.log('count: %d', count);\n// Prints: count: 5, to stdout\nconsole.log('count:', count);\n// Prints: count: 5, to stdout\nSee util.format() for more information.
Try to construct a table with the columns of the properties of tabularData\n(or use properties) and rows of tabularData and log it. Falls back to just\nlogging the argument if it can’t be parsed as tabular.
// These can't be parsed as tabular data\nconsole.table(Symbol());\n// Symbol()\n\nconsole.table(undefined);\n// undefined\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }]);\n// ┌─────────┬─────┬─────┐\n// │ (index) │ a │ b │\n// ├─────────┼─────┼─────┤\n// │ 0 │ 1 │ 'Y' │\n// │ 1 │ 'Z' │ 2 │\n// └─────────┴─────┴─────┘\n\nconsole.table([{ a: 1, b: 'Y' }, { a: 'Z', b: 2 }], ['a']);\n// ┌─────────┬─────┐\n// │ (index) │ a │\n// ├─────────┼─────┤\n// │ 0 │ 1 │\n// │ 1 │ 'Z' │\n// └─────────┴─────┘\nStarts a timer that can be used to compute the duration of an operation. Timers\nare identified by a unique label. Use the same label when calling\nconsole.timeEnd() to stop the timer and output the elapsed time in\nmilliseconds to stdout. Timer durations are accurate to the sub-millisecond.
Stops a timer that was previously started by calling console.time() and\nprints the result to stdout:
console.time('100-elements');\nfor (let i = 0; i < 100; i++) {}\nconsole.timeEnd('100-elements');\n// prints 100-elements: 225.438ms\nFor a timer that was previously started by calling console.time(), prints\nthe elapsed time and other data arguments to stdout:
console.time('process');\nconst value = expensiveProcess1(); // Returns 42\nconsole.timeLog('process', value);\n// Prints \"process: 365.227ms 42\".\ndoExpensiveProcess2(value);\nconsole.timeEnd('process');\nPrints to stderr the string 'Trace: ', followed by the util.format()\nformatted message and stack trace to the current position in the code.
console.trace('Show me');\n// Prints: (stack trace will vary based on where trace is called)\n// Trace: Show me\n// at repl:2:9\n// at REPLServer.defaultEval (repl.js:248:27)\n// at bound (domain.js:287:14)\n// at REPLServer.runBound [as eval] (domain.js:300:12)\n// at REPLServer.<anonymous> (repl.js:412:12)\n// at emitOne (events.js:82:20)\n// at REPLServer.emit (events.js:169:7)\n// at REPLServer.Interface._onLine (readline.js:210:10)\n// at REPLServer.Interface._line (readline.js:549:8)\n// at REPLServer.Interface._ttyWrite (readline.js:826:14)\nThe console.warn() function is an alias for console.error().
Creates a new Console with one or two writable stream instances. stdout is a\nwritable stream to print log or info output. stderr is used for warning or\nerror output. If stderr is not provided, stdout is used for stderr.
const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// in stdout.log: count 5\nThe global console is a special Console whose output is sent to\nprocess.stdout and process.stderr. It is equivalent to calling:
new Console({ stdout: process.stdout, stderr: process.stderr });\nCreates a new Console with one or two writable stream instances. stdout is a\nwritable stream to print log or info output. stderr is used for warning or\nerror output. If stderr is not provided, stdout is used for stderr.
const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// custom simple logger\nconst logger = new Console({ stdout: output, stderr: errorOutput });\n// use it like console\nconst count = 5;\nlogger.log('count: %d', count);\n// in stdout.log: count 5\nThe global console is a special Console whose output is sent to\nprocess.stdout and process.stderr. It is equivalent to calling:
new Console({ stdout: process.stdout, stderr: process.stderr });\nThe following methods are exposed by the V8 engine in the general API but do\nnot display anything unless used in conjunction with the inspector\n(--inspect flag).
This method does not display anything unless used in the inspector. The\nconsole.markTimeline() method is the deprecated form of\nconsole.timeStamp().
This method does not display anything unless used in the inspector. The\nconsole.profile() method starts a JavaScript CPU profile with an optional\nlabel until console.profileEnd() is called. The profile is then added to\nthe Profile panel of the inspector.
console.profile('MyLabel');\n// Some code\nconsole.profileEnd('MyLabel');\n// Adds the profile 'MyLabel' to the Profiles panel of the inspector.\nThis method does not display anything unless used in the inspector. Stops the\ncurrent JavaScript CPU profiling session if one has been started and prints\nthe report to the Profiles panel of the inspector. See\nconsole.profile() for an example.
If this method is called without a label, the most recently started profile is\nstopped.
" }, { "textRaw": "console.timeStamp([label])", "type": "method", "name": "timeStamp", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`label` {string}", "name": "label", "type": "string", "optional": true } ] } ], "desc": "This method does not display anything unless used in the inspector. The\nconsole.timeStamp() method adds an event with the label 'label' to the\nTimeline panel of the inspector.
This method does not display anything unless used in the inspector. The\nconsole.timeline() method is the deprecated form of console.time().
This method does not display anything unless used in the inspector. The\nconsole.timelineEnd() method is the deprecated form of\nconsole.timeEnd().
The crypto module provides cryptographic functionality that includes a set of\nwrappers for OpenSSL's hash, HMAC, cipher, decipher, sign, and verify functions.
Use require('crypto') to access this module.
const crypto = require('crypto');\n\nconst secret = 'abcdefg';\nconst hash = crypto.createHmac('sha256', secret)\n .update('I love cupcakes')\n .digest('hex');\nconsole.log(hash);\n// Prints:\n// c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e\nIt is possible for Node.js to be built without including support for the\ncrypto module. In such cases, calling require('crypto') will result in an\nerror being thrown.
let crypto;\ntry {\n crypto = require('crypto');\n} catch (err) {\n console.log('crypto support is disabled!');\n}\nThe default encoding to use for functions that can take either strings\nor buffers. The default value is 'buffer', which makes methods\ndefault to Buffer objects.
The crypto.DEFAULT_ENCODING mechanism is provided for backwards compatibility\nwith legacy programs that expect 'latin1' to be the default encoding.
New applications should expect the default to be 'buffer'.
This property is deprecated.
" }, { "textRaw": "crypto.fips", "name": "fips", "meta": { "added": [ "v6.0.0" ], "deprecated": [ "v10.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated", "desc": "Property for checking and controlling whether a FIPS compliant crypto provider\nis currently in use. Setting to true requires a FIPS build of Node.js.
\nThis property is deprecated. Please use crypto.setFips() and\ncrypto.getFips() instead.
Creates and returns a Cipher object that uses the given algorithm and\npassword.
The options argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode is used (e.g. 'aes-128-ccm'). In that case, the\nauthTagLength option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength\noption is not required but can be used to set the length of the authentication\ntag that will be returned by getAuthTag() and defaults to 16 bytes.
The algorithm is dependent on OpenSSL, examples are 'aes192', etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms\n(openssl list-cipher-algorithms for older versions of OpenSSL) will\ndisplay the available cipher algorithms.
The password is used to derive the cipher key and initialization vector (IV).\nThe value must be either a 'latin1' encoded string, a Buffer, a\nTypedArray, or a DataView.
The implementation of crypto.createCipher() derives keys using the OpenSSL\nfunction EVP_BytesToKey with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.
In line with OpenSSL's recommendation to use a more modern algorithm instead of\nEVP_BytesToKey it is recommended that developers derive a key and IV on\ntheir own using crypto.scrypt() and to use crypto.createCipheriv()\nto create the Cipher object. Users should not use ciphers with counter mode\n(e.g. CTR, GCM, or CCM) in crypto.createCipher(). A warning is emitted when\nthey are used in order to avoid the risk of IV reuse that causes\nvulnerabilities. For the case when IV is reused in GCM, see Nonce-Disrespecting\nAdversaries for details.
Creates and returns a Cipher object, with the given algorithm, key and\ninitialization vector (iv).
The options argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode is used (e.g. 'aes-128-ccm'). In that case, the\nauthTagLength option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength\noption is not required but can be used to set the length of the authentication\ntag that will be returned by getAuthTag() and defaults to 16 bytes.
The algorithm is dependent on OpenSSL, examples are 'aes192', etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms\n(openssl list-cipher-algorithms for older versions of OpenSSL) will\ndisplay the available cipher algorithms.
The key is the raw key used by the algorithm and iv is an\ninitialization vector. Both arguments must be 'utf8' encoded strings,\nBuffers, TypedArray, or DataViews. If the cipher does not need\nan initialization vector, iv may be null.
Initialization vectors should be unpredictable and unique; ideally, they will be\ncryptographically random. They do not have to be secret: IVs are typically just\nadded to ciphertext messages unencrypted. It may sound contradictory that\nsomething has to be unpredictable and unique, but does not have to be secret;\nit is important to remember that an attacker must not be able to predict ahead\nof time what a given IV will be.
" }, { "textRaw": "crypto.createCredentials(details)", "type": "method", "name": "createCredentials", "meta": { "added": [ "v0.1.92" ], "deprecated": [ "v0.11.13" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`tls.createSecureContext()`][] instead.", "signatures": [ { "return": { "textRaw": "Returns: {tls.SecureContext}", "name": "return", "type": "tls.SecureContext" }, "params": [ { "textRaw": "`details` {Object} Identical to [`tls.createSecureContext()`][].", "name": "details", "type": "Object", "desc": "Identical to [`tls.createSecureContext()`][]." } ] } ], "desc": "The crypto.createCredentials() method is a deprecated function for creating\nand returning a tls.SecureContext. It should not be used. Replace it with\ntls.createSecureContext() which has the exact same arguments and return\nvalue.
Returns a tls.SecureContext, as-if tls.createSecureContext() had been\ncalled.
Creates and returns a Decipher object that uses the given algorithm and\npassword (key).
The options argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode is used (e.g. 'aes-128-ccm'). In that case, the\nauthTagLength option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode.
The implementation of crypto.createDecipher() derives keys using the OpenSSL\nfunction EVP_BytesToKey with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.
In line with OpenSSL's recommendation to use a more modern algorithm instead of\nEVP_BytesToKey it is recommended that developers derive a key and IV on\ntheir own using crypto.scrypt() and to use crypto.createDecipheriv()\nto create the Decipher object.
Creates and returns a Decipher object that uses the given algorithm, key\nand initialization vector (iv).
The options argument controls stream behavior and is optional except when a\ncipher in CCM or OCB mode is used (e.g. 'aes-128-ccm'). In that case, the\nauthTagLength option is required and specifies the length of the\nauthentication tag in bytes, see CCM mode. In GCM mode, the authTagLength\noption is not required but can be used to restrict accepted authentication tags\nto those with the specified length.
The algorithm is dependent on OpenSSL, examples are 'aes192', etc. On\nrecent OpenSSL releases, openssl list -cipher-algorithms\n(openssl list-cipher-algorithms for older versions of OpenSSL) will\ndisplay the available cipher algorithms.
The key is the raw key used by the algorithm and iv is an\ninitialization vector. Both arguments must be 'utf8' encoded strings,\nBuffers, TypedArray, or DataViews. If the cipher does not need\nan initialization vector, iv may be null.
Initialization vectors should be unpredictable and unique; ideally, they will be\ncryptographically random. They do not have to be secret: IVs are typically just\nadded to ciphertext messages unencrypted. It may sound contradictory that\nsomething has to be unpredictable and unique, but does not have to be secret;\nit is important to remember that an attacker must not be able to predict ahead\nof time what a given IV will be.
" }, { "textRaw": "crypto.createDiffieHellman(prime[, primeEncoding][, generator][, generatorEncoding])", "type": "method", "name": "createDiffieHellman", "meta": { "added": [ "v0.11.12" ], "changes": [ { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/12223", "description": "The `prime` argument can be any `TypedArray` or `DataView` now." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11983", "description": "The `prime` argument can be a `Uint8Array` now." }, { "version": "v6.0.0", "pr-url": "https://github.com/nodejs/node/pull/5522", "description": "The default for the encoding parameters changed from `binary` to `utf8`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {DiffieHellman}", "name": "return", "type": "DiffieHellman" }, "params": [ { "textRaw": "`prime` {string | Buffer | TypedArray | DataView}", "name": "prime", "type": "string | Buffer | TypedArray | DataView" }, { "textRaw": "`primeEncoding` {string} The [encoding][] of the `prime` string.", "name": "primeEncoding", "type": "string", "desc": "The [encoding][] of the `prime` string.", "optional": true }, { "textRaw": "`generator` {number | string | Buffer | TypedArray | DataView} **Default:** `2`", "name": "generator", "type": "number | string | Buffer | TypedArray | DataView", "default": "`2`", "optional": true }, { "textRaw": "`generatorEncoding` {string} The [encoding][] of the `generator` string.", "name": "generatorEncoding", "type": "string", "desc": "The [encoding][] of the `generator` string.", "optional": true } ] } ], "desc": "Creates a DiffieHellman key exchange object using the supplied prime and an\noptional specific generator.
The generator argument can be a number, string, or Buffer. If\ngenerator is not specified, the value 2 is used.
If primeEncoding is specified, prime is expected to be a string; otherwise\na Buffer, TypedArray, or DataView is expected.
If generatorEncoding is specified, generator is expected to be a string;\notherwise a number, Buffer, TypedArray, or DataView is expected.
Creates a DiffieHellman key exchange object and generates a prime of\nprimeLength bits using an optional specific numeric generator.\nIf generator is not specified, the value 2 is used.
Creates an Elliptic Curve Diffie-Hellman (ECDH) key exchange object using a\npredefined curve specified by the curveName string. Use\ncrypto.getCurves() to obtain a list of available curve names. On recent\nOpenSSL releases, openssl ecparam -list_curves will also display the name\nand description of each available elliptic curve.
Creates and returns a Hash object that can be used to generate hash digests\nusing the given algorithm. Optional options argument controls stream\nbehavior.
The algorithm is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256', 'sha512', etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms\n(openssl list-message-digest-algorithms for older versions of OpenSSL) will\ndisplay the available digest algorithms.
Example: generating the sha256 sum of a file
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hash.update(data);\n else {\n console.log(`${hash.digest('hex')} ${filename}`);\n }\n});\nCreates and returns an Hmac object that uses the given algorithm and key.\nOptional options argument controls stream behavior.
The algorithm is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256', 'sha512', etc.\nOn recent releases of OpenSSL, openssl list -digest-algorithms\n(openssl list-message-digest-algorithms for older versions of OpenSSL) will\ndisplay the available digest algorithms.
The key is the HMAC key used to generate the cryptographic HMAC hash.
Example: generating the sha256 HMAC of a file
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = input.read();\n if (data)\n hmac.update(data);\n else {\n console.log(`${hmac.digest('hex')} ${filename}`);\n }\n});\nCreates and returns a Sign object that uses the given algorithm.\nUse crypto.getHashes() to obtain an array of names of the available\nsigning algorithms. Optional options argument controls the\nstream.Writable behavior.
Creates and returns a Verify object that uses the given algorithm.\nUse crypto.getHashes() to obtain an array of names of the available\nsigning algorithms. Optional options argument controls the\nstream.Writable behavior.
Generates a new asymmetric key pair of the given type. Only RSA, DSA and EC\nare currently supported.
It is recommended to encode public keys as 'spki' and private keys as\n'pkcs8' with encryption:
const { generateKeyPair } = require('crypto');\ngenerateKeyPair('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem'\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret'\n }\n}, (err, publicKey, privateKey) => {\n // Handle errors and use the generated key pair.\n});\nOn completion, callback will be called with err set to undefined and\npublicKey / privateKey representing the generated key pair. When PEM\nencoding was selected, the result will be a string, otherwise it will be a\nbuffer containing the data encoded as DER. Note that Node.js itself does not\naccept DER, it is supported for interoperability with other libraries such as\nWebCrypto only.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with publicKey and privateKey properties.
Generates a new asymmetric key pair of the given type. Only RSA, DSA and EC\nare currently supported.
It is recommended to encode public keys as 'spki' and private keys as\n'pkcs8' with encryption:
const { generateKeyPairSync } = require('crypto');\nconst { publicKey, privateKey } = generateKeyPairSync('rsa', {\n modulusLength: 4096,\n publicKeyEncoding: {\n type: 'spki',\n format: 'pem'\n },\n privateKeyEncoding: {\n type: 'pkcs8',\n format: 'pem',\n cipher: 'aes-256-cbc',\n passphrase: 'top secret'\n }\n});\nThe return value { publicKey, privateKey } represents the generated key pair.\nWhen PEM encoding was selected, the respective key will be a string, otherwise\nit will be a buffer containing the data encoded as DER.
const ciphers = crypto.getCiphers();\nconsole.log(ciphers); // ['aes-128-cbc', 'aes-128-ccm', ...]\nconst curves = crypto.getCurves();\nconsole.log(curves); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]\nCreates a predefined DiffieHellman key exchange object. The\nsupported groups are: 'modp1', 'modp2', 'modp5' (defined in\nRFC 2412, but see Caveats) and 'modp14', 'modp15',\n'modp16', 'modp17', 'modp18' (defined in RFC 3526). The\nreturned object mimics the interface of objects created by\ncrypto.createDiffieHellman(), but will not allow changing\nthe keys (with diffieHellman.setPublicKey(), for example). The\nadvantage of using this method is that the parties do not have to\ngenerate nor exchange a group modulus beforehand, saving both processor\nand communication time.
Example (obtaining a shared secret):
\nconst crypto = require('crypto');\nconst alice = crypto.getDiffieHellman('modp14');\nconst bob = crypto.getDiffieHellman('modp14');\n\nalice.generateKeys();\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n/* aliceSecret and bobSecret should be the same */\nconsole.log(aliceSecret === bobSecret);\nconst hashes = crypto.getHashes();\nconsole.log(hashes); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]\nProvides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest is\napplied to derive a key of the requested byte length (keylen) from the\npassword, salt and iterations.
The supplied callback function is called with two arguments: err and\nderivedKey. If an error occurs while deriving the key, err will be set;\notherwise err will be null. By default, the successfully generated\nderivedKey will be passed to the callback as a Buffer. An error will be\nthrown if any of the input arguments specify invalid values or types.
If digest is null, 'sha1' will be used. This behavior will be deprecated\nin a future version of Node.js.
The iterations argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.
The salt should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
const crypto = require('crypto');\ncrypto.pbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\nThe crypto.DEFAULT_ENCODING property can be used to change the way the\nderivedKey is passed to the callback. This property, however, has been\ndeprecated and use should be avoided.
const crypto = require('crypto');\ncrypto.DEFAULT_ENCODING = 'hex';\ncrypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey); // '3745e48...aa39b34'\n});\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes().
Note that this API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications, see the\nUV_THREADPOOL_SIZE documentation for more information.
Provides a synchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest is\napplied to derive a key of the requested byte length (keylen) from the\npassword, salt and iterations.
If an error occurs an Error will be thrown, otherwise the derived key will be\nreturned as a Buffer.
If digest is null, 'sha1' will be used. This behavior will be deprecated\nin a future version of Node.js.
The iterations argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.
The salt should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
const crypto = require('crypto');\nconst key = crypto.pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');\nconsole.log(key.toString('hex')); // '3745e48...08d59ae'\nThe crypto.DEFAULT_ENCODING property may be used to change the way the\nderivedKey is returned. This property, however, is deprecated and use\nshould be avoided.
const crypto = require('crypto');\ncrypto.DEFAULT_ENCODING = 'hex';\nconst key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');\nconsole.log(key); // '3745e48...aa39b34'\nAn array of supported digest functions can be retrieved using\ncrypto.getHashes().
Decrypts buffer with privateKey. buffer was previously encrypted using\nthe corresponding public key, for example using crypto.publicEncrypt().
privateKey can be an object or a string. If privateKey is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING.
Encrypts buffer with privateKey. The returned data can be decrypted using\nthe corresponding public key, for example using crypto.publicDecrypt().
privateKey can be an object or a string. If privateKey is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_PADDING.
Decrypts buffer with key.buffer was previously encrypted using\nthe corresponding private key, for example using crypto.privateEncrypt().
key can be an object or a string. If key is a string, it is treated as\nthe key with no passphrase and will use RSA_PKCS1_PADDING.
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.
" }, { "textRaw": "crypto.publicEncrypt(key, buffer)", "type": "method", "name": "publicEncrypt", "meta": { "added": [ "v0.11.14" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer} A new `Buffer` with the encrypted content.", "name": "return", "type": "Buffer", "desc": "A new `Buffer` with the encrypted content." }, "params": [ { "textRaw": "`key` {Object | string}", "name": "key", "type": "Object | string", "options": [ { "textRaw": "`key` {string} A PEM encoded public or private key.", "name": "key", "type": "string", "desc": "A PEM encoded public or private key." }, { "textRaw": "`passphrase` {string} An optional passphrase for the private key.", "name": "passphrase", "type": "string", "desc": "An optional passphrase for the private key." }, { "textRaw": "`padding` {crypto.constants} An optional padding value defined in `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`, `crypto.constants.RSA_PKCS1_PADDING`, or `crypto.constants.RSA_PKCS1_OAEP_PADDING`.", "name": "padding", "type": "crypto.constants", "desc": "An optional padding value defined in `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`, `crypto.constants.RSA_PKCS1_PADDING`, or `crypto.constants.RSA_PKCS1_OAEP_PADDING`." } ] }, { "textRaw": "`buffer` {Buffer | TypedArray | DataView}", "name": "buffer", "type": "Buffer | TypedArray | DataView" } ] } ], "desc": "Encrypts the content of buffer with key and returns a new\nBuffer with encrypted content. The returned data can be decrypted using\nthe corresponding private key, for example using crypto.privateDecrypt().
key can be an object or a string. If key is a string, it is treated as\nthe key with no passphrase and will use RSA_PKCS1_OAEP_PADDING.
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.
" }, { "textRaw": "crypto.randomBytes(size[, callback])", "type": "method", "name": "randomBytes", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/16454", "description": "Passing `null` as the `callback` argument now throws `ERR_INVALID_CALLBACK`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer} if the `callback` function is not provided.", "name": "return", "type": "Buffer", "desc": "if the `callback` function is not provided." }, "params": [ { "textRaw": "`size` {number}", "name": "size", "type": "number" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`buf` {Buffer}", "name": "buf", "type": "Buffer" } ], "optional": true } ] } ], "desc": "Generates cryptographically strong pseudo-random data. The size argument\nis a number indicating the number of bytes to generate.
If a callback function is provided, the bytes are generated asynchronously\nand the callback function is invoked with two arguments: err and buf.\nIf an error occurs, err will be an Error object; otherwise it is null. The\nbuf argument is a Buffer containing the generated bytes.
// Asynchronous\nconst crypto = require('crypto');\ncrypto.randomBytes(256, (err, buf) => {\n if (err) throw err;\n console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);\n});\nIf the callback function is not provided, the random bytes are generated\nsynchronously and returned as a Buffer. An error will be thrown if\nthere is a problem generating the bytes.
// Synchronous\nconst buf = crypto.randomBytes(256);\nconsole.log(\n `${buf.length} bytes of random data: ${buf.toString('hex')}`);\nThe crypto.randomBytes() method will not complete until there is\nsufficient entropy available.\nThis should normally never take longer than a few milliseconds. The only time\nwhen generating the random bytes may conceivably block for a longer period of\ntime is right after boot, when the whole system is still low on entropy.
Note that this API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications, see the\nUV_THREADPOOL_SIZE documentation for more information.
The asynchronous version of crypto.randomBytes() is carried out in a single\nthreadpool request. To minimize threadpool task length variation, partition\nlarge randomBytes requests when doing so as part of fulfilling a client\nrequest.
Synchronous version of crypto.randomFill().
const buf = Buffer.alloc(10);\nconsole.log(crypto.randomFillSync(buf).toString('hex'));\n\ncrypto.randomFillSync(buf, 5);\nconsole.log(buf.toString('hex'));\n\n// The above is equivalent to the following:\ncrypto.randomFillSync(buf, 5, 5);\nconsole.log(buf.toString('hex'));\nAny TypedArray or DataView instance may be passed as buffer.
const a = new Uint32Array(10);\nconsole.log(Buffer.from(crypto.randomFillSync(a).buffer,\n a.byteOffset, a.byteLength).toString('hex'));\n\nconst b = new Float64Array(10);\nconsole.log(Buffer.from(crypto.randomFillSync(b).buffer,\n b.byteOffset, b.byteLength).toString('hex'));\n\nconst c = new DataView(new ArrayBuffer(10));\nconsole.log(Buffer.from(crypto.randomFillSync(c).buffer,\n c.byteOffset, c.byteLength).toString('hex'));\nThis function is similar to crypto.randomBytes() but requires the first\nargument to be a Buffer that will be filled. It also\nrequires that a callback is passed in.
If the callback function is not provided, an error will be thrown.
const buf = Buffer.alloc(10);\ncrypto.randomFill(buf, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\ncrypto.randomFill(buf, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\n\n// The above is equivalent to the following:\ncrypto.randomFill(buf, 5, 5, (err, buf) => {\n if (err) throw err;\n console.log(buf.toString('hex'));\n});\nAny TypedArray or DataView instance may be passed as buffer.
const a = new Uint32Array(10);\ncrypto.randomFill(a, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst b = new Float64Array(10);\ncrypto.randomFill(b, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\n\nconst c = new DataView(new ArrayBuffer(10));\ncrypto.randomFill(c, (err, buf) => {\n if (err) throw err;\n console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)\n .toString('hex'));\n});\nNote that this API uses libuv's threadpool, which can have surprising and\nnegative performance implications for some applications, see the\nUV_THREADPOOL_SIZE documentation for more information.
The asynchronous version of crypto.randomFill() is carried out in a single\nthreadpool request. To minimize threadpool task length variation, partition\nlarge randomFill requests when doing so as part of fulfilling a client\nrequest.
Provides an asynchronous scrypt implementation. Scrypt is a password-based\nkey derivation function that is designed to be expensive computationally and\nmemory-wise in order to make brute-force attacks unrewarding.
\nThe salt should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
The callback function is called with two arguments: err and derivedKey.\nerr is an exception object when key derivation fails, otherwise err is\nnull. derivedKey is passed to the callback as a Buffer.
An exception is thrown when any of the input arguments specify invalid values\nor types.
\nconst crypto = require('crypto');\n// Using the factory defaults.\ncrypto.scrypt('secret', 'salt', 64, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...08d59ae'\n});\n// Using a custom N parameter. Must be a power of two.\ncrypto.scrypt('secret', 'salt', 64, { N: 1024 }, (err, derivedKey) => {\n if (err) throw err;\n console.log(derivedKey.toString('hex')); // '3745e48...aa39b34'\n});\nProvides a synchronous scrypt implementation. Scrypt is a password-based\nkey derivation function that is designed to be expensive computationally and\nmemory-wise in order to make brute-force attacks unrewarding.
\nThe salt should be as unique as possible. It is recommended that a salt is\nrandom and at least 16 bytes long. See NIST SP 800-132 for details.
An exception is thrown when key derivation fails, otherwise the derived key is\nreturned as a Buffer.
An exception is thrown when any of the input arguments specify invalid values\nor types.
\nconst crypto = require('crypto');\n// Using the factory defaults.\nconst key1 = crypto.scryptSync('secret', 'salt', 64);\nconsole.log(key1.toString('hex')); // '3745e48...08d59ae'\n// Using a custom N parameter. Must be a power of two.\nconst key2 = crypto.scryptSync('secret', 'salt', 64, { N: 1024 });\nconsole.log(key2.toString('hex')); // '3745e48...aa39b34'\nLoad and set the engine for some or all OpenSSL functions (selected by flags).
engine could be either an id or a path to the engine's shared library.
The optional flags argument uses ENGINE_METHOD_ALL by default. The flags\nis a bit field taking one of or a mix of the following flags (defined in\ncrypto.constants):
crypto.constants.ENGINE_METHOD_RSAcrypto.constants.ENGINE_METHOD_DSAcrypto.constants.ENGINE_METHOD_DHcrypto.constants.ENGINE_METHOD_RANDcrypto.constants.ENGINE_METHOD_ECcrypto.constants.ENGINE_METHOD_CIPHERScrypto.constants.ENGINE_METHOD_DIGESTScrypto.constants.ENGINE_METHOD_PKEY_METHScrypto.constants.ENGINE_METHOD_PKEY_ASN1_METHScrypto.constants.ENGINE_METHOD_ALLcrypto.constants.ENGINE_METHOD_NONEThe flags below are deprecated in OpenSSL-1.1.0.
\ncrypto.constants.ENGINE_METHOD_ECDHcrypto.constants.ENGINE_METHOD_ECDSAcrypto.constants.ENGINE_METHOD_STOREEnables the FIPS compliant crypto provider in a FIPS-enabled Node.js build.\nThrows an error if FIPS mode is not available.
" }, { "textRaw": "crypto.timingSafeEqual(a, b)", "type": "method", "name": "timingSafeEqual", "meta": { "added": [ "v6.6.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`a` {Buffer | TypedArray | DataView}", "name": "a", "type": "Buffer | TypedArray | DataView" }, { "textRaw": "`b` {Buffer | TypedArray | DataView}", "name": "b", "type": "Buffer | TypedArray | DataView" } ] } ], "desc": "This function is based on a constant-time algorithm.\nReturns true if a is equal to b, without leaking timing information that\nwould allow an attacker to guess one of the values. This is suitable for\ncomparing HMAC digests or secret values like authentication cookies or\ncapability urls.
a and b must both be Buffers, TypedArrays, or DataViews, and they\nmust have the same length.
Use of crypto.timingSafeEqual does not guarantee that the surrounding code\nis timing-safe. Care should be taken to ensure that the surrounding code does\nnot introduce timing vulnerabilities.
The Crypto module was added to Node.js before there was the concept of a\nunified Stream API, and before there were Buffer objects for handling\nbinary data. As such, the many of the crypto defined classes have methods not\ntypically found on other Node.js classes that implement the streams\nAPI (e.g. update(), final(), or digest()). Also, many methods accepted\nand returned 'latin1' encoded strings by default rather than Buffers. This\ndefault was changed after Node.js v0.8 to use Buffer objects by default\ninstead.
Usage of ECDH with non-dynamically generated key pairs has been simplified.\nNow, ecdh.setPrivateKey() can be called with a preselected private key\nand the associated public point (key) will be computed and stored in the object.\nThis allows code to only store and provide the private part of the EC key pair.\necdh.setPrivateKey() now also validates that the private key is valid for\nthe selected curve.
The ecdh.setPublicKey() method is now deprecated as its inclusion in the\nAPI is not useful. Either a previously stored private key should be set, which\nautomatically generates the associated public key, or ecdh.generateKeys()\nshould be called. The main drawback of using ecdh.setPublicKey() is that\nit can be used to put the ECDH key pair into an inconsistent state.
The crypto module still supports some algorithms which are already\ncompromised and are not currently recommended for use. The API also allows\nthe use of ciphers and hashes with a small key size that are considered to be\ntoo weak for safe use.
Users should take full responsibility for selecting the crypto\nalgorithm and key size according to their security requirements.
\nBased on the recommendations of NIST SP 800-131A:
\nmodp1, modp2 and modp5 have a key size\nsmaller than 2048 bits and are not recommended.See the reference for other recommendations and details.
", "type": "module", "displayName": "Support for weak or compromised algorithms" }, { "textRaw": "CCM mode", "name": "ccm_mode", "desc": "CCM is one of the supported AEAD algorithms. Applications which use this\nmode must adhere to certain restrictions when using the cipher API:
\nauthTagLength option and must be one of 4, 6, 8, 10, 12, 14 or\n16 bytes.N must be between 7 and 13\nbytes (7 ≤ N ≤ 13).2 ** (8 * (15 - N)) bytes.setAuthTag() before\nspecifying additional authenticated data or calling update().\nOtherwise, decryption will fail and final() will throw an error in\ncompliance with section 2.6 of RFC 3610.write(data), end(data) or pipe() in CCM\nmode might fail as CCM cannot handle more than one chunk of data per instance.setAAD() via the plaintextLength\noption. This is not necessary if no AAD is used.update() can only be called\nonce.update() is sufficient to encrypt/decrypt the message,\napplications must call final() to compute or verify the\nauthentication tag.const crypto = require('crypto');\n\nconst key = 'keykeykeykeykeykeykeykey';\nconst nonce = crypto.randomBytes(12);\n\nconst aad = Buffer.from('0123456789', 'hex');\n\nconst cipher = crypto.createCipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16\n});\nconst plaintext = 'Hello world';\ncipher.setAAD(aad, {\n plaintextLength: Buffer.byteLength(plaintext)\n});\nconst ciphertext = cipher.update(plaintext, 'utf8');\ncipher.final();\nconst tag = cipher.getAuthTag();\n\n// Now transmit { ciphertext, nonce, tag }.\n\nconst decipher = crypto.createDecipheriv('aes-192-ccm', key, nonce, {\n authTagLength: 16\n});\ndecipher.setAuthTag(tag);\ndecipher.setAAD(aad, {\n plaintextLength: ciphertext.length\n});\nconst receivedPlaintext = decipher.update(ciphertext, null, 'utf8');\n\ntry {\n decipher.final();\n} catch (err) {\n console.error('Authentication failed!');\n}\n\nconsole.log(receivedPlaintext);\nThe following constants exported by crypto.constants apply to various uses of\nthe crypto, tls, and https modules and are generally specific to OpenSSL.
| Constant | \nDescription | \n
|---|---|
SSL_OP_ALL | \n Applies multiple bug workarounds within OpenSSL. See\n https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html\n for detail. | \n
SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION | \n Allows legacy insecure renegotiation between OpenSSL and unpatched\n clients or servers. See\n https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html. | \n
SSL_OP_CIPHER_SERVER_PREFERENCE | \n Attempts to use the server's preferences instead of the client's when\n selecting a cipher. Behavior depends on protocol version. See\n https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html. | \n
SSL_OP_CISCO_ANYCONNECT | \n Instructs OpenSSL to use Cisco's \"speshul\" version of DTLS_BAD_VER. | \n
SSL_OP_COOKIE_EXCHANGE | \n Instructs OpenSSL to turn on cookie exchange. | \n
SSL_OP_CRYPTOPRO_TLSEXT_BUG | \n Instructs OpenSSL to add server-hello extension from an early version\n of the cryptopro draft. | \n
SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS | \n Instructs OpenSSL to disable a SSL 3.0/TLS 1.0 vulnerability\n workaround added in OpenSSL 0.9.6d. | \n
SSL_OP_EPHEMERAL_RSA | \n Instructs OpenSSL to always use the tmp_rsa key when performing RSA\n operations. | \n
SSL_OP_LEGACY_SERVER_CONNECT | \n Allows initial connection to servers that do not support RI. | \n
SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER | \n \n |
SSL_OP_MICROSOFT_SESS_ID_BUG | \n \n |
SSL_OP_MSIE_SSLV2_RSA_PADDING | \n Instructs OpenSSL to disable the workaround for a man-in-the-middle\n protocol-version vulnerability in the SSL 2.0 server implementation. | \n
SSL_OP_NETSCAPE_CA_DN_BUG | \n \n |
SSL_OP_NETSCAPE_CHALLENGE_BUG | \n \n |
SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG | \n \n |
SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG | \n \n |
SSL_OP_NO_COMPRESSION | \n Instructs OpenSSL to disable support for SSL/TLS compression. | \n
SSL_OP_NO_QUERY_MTU | \n \n |
SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION | \n Instructs OpenSSL to always start a new session when performing\n renegotiation. | \n
SSL_OP_NO_SSLv2 | \n Instructs OpenSSL to turn off SSL v2 | \n
SSL_OP_NO_SSLv3 | \n Instructs OpenSSL to turn off SSL v3 | \n
SSL_OP_NO_TICKET | \n Instructs OpenSSL to disable use of RFC4507bis tickets. | \n
SSL_OP_NO_TLSv1 | \n Instructs OpenSSL to turn off TLS v1 | \n
SSL_OP_NO_TLSv1_1 | \n Instructs OpenSSL to turn off TLS v1.1 | \n
SSL_OP_NO_TLSv1_2 | \n Instructs OpenSSL to turn off TLS v1.2 | \nSSL_OP_PKCS1_CHECK_1 | \n \n \n |
SSL_OP_PKCS1_CHECK_2 | \n \n |
SSL_OP_SINGLE_DH_USE | \n Instructs OpenSSL to always create a new key when using\n temporary/ephemeral DH parameters. | \n
SSL_OP_SINGLE_ECDH_USE | \n Instructs OpenSSL to always create a new key when using\n temporary/ephemeral ECDH parameters. | \nSSL_OP_SSLEAY_080_CLIENT_DH_BUG | \n \n \n |
SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG | \n \n |
SSL_OP_TLS_BLOCK_PADDING_BUG | \n \n |
SSL_OP_TLS_D5_BUG | \n \n |
SSL_OP_TLS_ROLLBACK_BUG | \n Instructs OpenSSL to disable version rollback attack detection. | \n
| Constant | \nDescription | \n
|---|---|
ENGINE_METHOD_RSA | \n Limit engine usage to RSA | \n
ENGINE_METHOD_DSA | \n Limit engine usage to DSA | \n
ENGINE_METHOD_DH | \n Limit engine usage to DH | \n
ENGINE_METHOD_RAND | \n Limit engine usage to RAND | \n
ENGINE_METHOD_EC | \n Limit engine usage to EC | \n
ENGINE_METHOD_CIPHERS | \n Limit engine usage to CIPHERS | \n
ENGINE_METHOD_DIGESTS | \n Limit engine usage to DIGESTS | \n
ENGINE_METHOD_PKEY_METHS | \n Limit engine usage to PKEY_METHDS | \n
ENGINE_METHOD_PKEY_ASN1_METHS | \n Limit engine usage to PKEY_ASN1_METHS | \n
ENGINE_METHOD_ALL | \n \n |
ENGINE_METHOD_NONE | \n \n |
| Constant | \nDescription | \n
|---|---|
DH_CHECK_P_NOT_SAFE_PRIME | \n \n |
DH_CHECK_P_NOT_PRIME | \n \n |
DH_UNABLE_TO_CHECK_GENERATOR | \n \n |
DH_NOT_SUITABLE_GENERATOR | \n \n |
ALPN_ENABLED | \n \n |
RSA_PKCS1_PADDING | \n \n |
RSA_SSLV23_PADDING | \n \n |
RSA_NO_PADDING | \n \n |
RSA_PKCS1_OAEP_PADDING | \n \n |
RSA_X931_PADDING | \n \n |
RSA_PKCS1_PSS_PADDING | \n \n |
RSA_PSS_SALTLEN_DIGEST | \n Sets the salt length for RSA_PKCS1_PSS_PADDING to the\n digest size when signing or verifying. | \n
RSA_PSS_SALTLEN_MAX_SIGN | \n Sets the salt length for RSA_PKCS1_PSS_PADDING to the\n maximum permissible value when signing data. | \n
RSA_PSS_SALTLEN_AUTO | \n Causes the salt length for RSA_PKCS1_PSS_PADDING to be\n determined automatically when verifying a signature. | \n
POINT_CONVERSION_COMPRESSED | \n \n |
POINT_CONVERSION_UNCOMPRESSED | \n \n |
POINT_CONVERSION_HYBRID | \n \n |
| Constant | \nDescription | \n
|---|---|
defaultCoreCipherList | \n Specifies the built-in default cipher list used by Node.js. | \n
defaultCipherList | \n Specifies the active default cipher list used by the current Node.js\n process. | \n
SPKAC is a Certificate Signing Request mechanism originally implemented by\nNetscape and was specified formally as part of HTML5's keygen element.
Note that <keygen> is deprecated since HTML 5.2 and new projects\nshould not use this element anymore.
The crypto module provides the Certificate class for working with SPKAC\ndata. The most common usage is handling output generated by the HTML5\n<keygen> element. Node.js uses OpenSSL's SPKAC implementation internally.
const { Certificate } = require('crypto');\nconst spkac = getSpkacSomehow();\nconst challenge = Certificate.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\nconst { Certificate } = require('crypto');\nconst spkac = getSpkacSomehow();\nconst publicKey = Certificate.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\nconst { Certificate } = require('crypto');\nconst spkac = getSpkacSomehow();\nconsole.log(Certificate.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\nAs a still supported legacy interface, it is possible (but not recommended) to\ncreate new instances of the crypto.Certificate class as illustrated in the\nexamples below.
Instances of the Certificate class can be created using the new keyword\nor by calling crypto.Certificate() as a function:
const crypto = require('crypto');\n\nconst cert1 = new crypto.Certificate();\nconst cert2 = crypto.Certificate();\nconst cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconst challenge = cert.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n// Prints: the challenge as a UTF8 string\nconst cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconst publicKey = cert.exportPublicKey(spkac);\nconsole.log(publicKey);\n// Prints: the public key as <Buffer ...>\nconst cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconsole.log(cert.verifySpkac(Buffer.from(spkac)));\n// Prints: true or false\nInstances of the Cipher class are used to encrypt data. The class can be\nused in one of two ways:
cipher.update() and cipher.final() methods to produce\nthe encrypted data.The crypto.createCipher() or crypto.createCipheriv() methods are\nused to create Cipher instances. Cipher objects are not to be created\ndirectly using the new keyword.
Example: Using Cipher objects as streams:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Key length is dependent on the algorithm. In this case for aes192, it is\n// 24 bytes (192 bits).\n// Use async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes()` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nlet encrypted = '';\ncipher.on('readable', () => {\n let chunk;\n while (null !== (chunk = cipher.read())) {\n encrypted += chunk.toString('hex');\n }\n});\ncipher.on('end', () => {\n console.log(encrypted);\n // Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa\n});\n\ncipher.write('some clear text data');\ncipher.end();\nExample: Using Cipher and piped streams:
const crypto = require('crypto');\nconst fs = require('fs');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes()` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nconst input = fs.createReadStream('test.js');\nconst output = fs.createWriteStream('test.enc');\n\ninput.pipe(cipher).pipe(output);\nExample: Using the cipher.update() and cipher.final() methods:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// Use `crypto.randomBytes` to generate a random iv instead of the static iv\n// shown here.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst cipher = crypto.createCipheriv(algorithm, key, iv);\n\nlet encrypted = cipher.update('some clear text data', 'utf8', 'hex');\nencrypted += cipher.final('hex');\nconsole.log(encrypted);\n// Prints: e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa\nOnce the cipher.final() method has been called, the Cipher object can no\nlonger be used to encrypt data. Attempts to call cipher.final() more than\nonce will result in an error being thrown.
When using an authenticated encryption mode (GCM, CCM and OCB are\ncurrently supported), the cipher.setAAD() method sets the value used for the\nadditional authenticated data (AAD) input parameter.
The options argument is optional for GCM and OCB. When using CCM, the\nplaintextLength option must be specified and its value must match the length\nof the plaintext in bytes. See CCM mode.
The cipher.setAAD() method must be called before cipher.update().
The cipher.getAuthTag() method should only be called after encryption has\nbeen completed using the cipher.final() method.
When using block encryption algorithms, the Cipher class will automatically\nadd padding to the input data to the appropriate block size. To disable the\ndefault padding call cipher.setAutoPadding(false).
When autoPadding is false, the length of the entire input data must be a\nmultiple of the cipher's block size or cipher.final() will throw an error.\nDisabling automatic padding is useful for non-standard padding, for instance\nusing 0x0 instead of PKCS padding.
The cipher.setAutoPadding() method must be called before\ncipher.final().
Updates the cipher with data. If the inputEncoding argument is given,\nthe data\nargument is a string using the specified encoding. If the inputEncoding\nargument is not given, data must be a Buffer, TypedArray, or\nDataView. If data is a Buffer, TypedArray, or DataView, then\ninputEncoding is ignored.
The outputEncoding specifies the output format of the enciphered\ndata. If the outputEncoding\nis specified, a string using the specified encoding is returned. If no\noutputEncoding is provided, a Buffer is returned.
The cipher.update() method can be called multiple times with new data until\ncipher.final() is called. Calling cipher.update() after\ncipher.final() will result in an error being thrown.
Instances of the Decipher class are used to decrypt data. The class can be\nused in one of two ways:
decipher.update() and decipher.final() methods to\nproduce the unencrypted data.The crypto.createDecipher() or crypto.createDecipheriv() methods are\nused to create Decipher instances. Decipher objects are not to be created\ndirectly using the new keyword.
Example: Using Decipher objects as streams:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Key length is dependent on the algorithm. In this case for aes192, it is\n// 24 bytes (192 bits).\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = crypto.createDecipheriv(algorithm, key, iv);\n\nlet decrypted = '';\ndecipher.on('readable', () => {\n while (null !== (chunk = decipher.read())) {\n decrypted += chunk.toString('utf8');\n }\n});\ndecipher.on('end', () => {\n console.log(decrypted);\n // Prints: some clear text data\n});\n\n// Encrypted with same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\ndecipher.write(encrypted, 'hex');\ndecipher.end();\nExample: Using Decipher and piped streams:
const crypto = require('crypto');\nconst fs = require('fs');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = crypto.createDecipheriv(algorithm, key, iv);\n\nconst input = fs.createReadStream('test.enc');\nconst output = fs.createWriteStream('test.js');\n\ninput.pipe(decipher).pipe(output);\nExample: Using the decipher.update() and decipher.final() methods:
const crypto = require('crypto');\n\nconst algorithm = 'aes-192-cbc';\nconst password = 'Password used to generate key';\n// Use the async `crypto.scrypt()` instead.\nconst key = crypto.scryptSync(password, 'salt', 24);\n// The IV is usually passed along with the ciphertext.\nconst iv = Buffer.alloc(16, 0); // Initialization vector.\n\nconst decipher = crypto.createDecipheriv(algorithm, key, iv);\n\n// Encrypted using same algorithm, key and iv.\nconst encrypted =\n 'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';\nlet decrypted = decipher.update(encrypted, 'hex', 'utf8');\ndecrypted += decipher.final('utf8');\nconsole.log(decrypted);\n// Prints: some clear text data\nOnce the decipher.final() method has been called, the Decipher object can\nno longer be used to decrypt data. Attempts to call decipher.final() more\nthan once will result in an error being thrown.
When using an authenticated encryption mode (GCM, CCM and OCB are\ncurrently supported), the decipher.setAAD() method sets the value used for the\nadditional authenticated data (AAD) input parameter.
The options argument is optional for GCM. When using CCM, the\nplaintextLength option must be specified and its value must match the length\nof the plaintext in bytes. See CCM mode.
The decipher.setAAD() method must be called before decipher.update().
When using an authenticated encryption mode (GCM, CCM and OCB are\ncurrently supported), the decipher.setAuthTag() method is used to pass in the\nreceived authentication tag. If no tag is provided, or if the cipher text\nhas been tampered with, decipher.final() will throw, indicating that the\ncipher text should be discarded due to failed authentication.
Note that this Node.js version does not verify the length of GCM authentication\ntags. Such a check must be implemented by applications and is crucial to the\nauthenticity of the encrypted data, otherwise, an attacker can use an\narbitrarily short authentication tag to increase the chances of successfully\npassing authentication (up to 0.39%). It is highly recommended to associate one\nof the values 16, 15, 14, 13, 12, 8 or 4 bytes with each key, and to only permit\nauthentication tags of that length, see NIST SP 800-38D.
\nThe decipher.setAuthTag() method must be called before\ndecipher.final().
When data has been encrypted without standard block padding, calling\ndecipher.setAutoPadding(false) will disable automatic padding to prevent\ndecipher.final() from checking for and removing padding.
Turning auto padding off will only work if the input data's length is a\nmultiple of the ciphers block size.
\nThe decipher.setAutoPadding() method must be called before\ndecipher.final().
Updates the decipher with data. If the inputEncoding argument is given,\nthe data\nargument is a string using the specified encoding. If the inputEncoding\nargument is not given, data must be a Buffer. If data is a\nBuffer then inputEncoding is ignored.
The outputEncoding specifies the output format of the enciphered\ndata. If the outputEncoding\nis specified, a string using the specified encoding is returned. If no\noutputEncoding is provided, a Buffer is returned.
The decipher.update() method can be called multiple times with new data until\ndecipher.final() is called. Calling decipher.update() after\ndecipher.final() will result in an error being thrown.
The DiffieHellman class is a utility for creating Diffie-Hellman key\nexchanges.
Instances of the DiffieHellman class can be created using the\ncrypto.createDiffieHellman() function.
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createDiffieHellman(2048);\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.createDiffieHellman(alice.getPrime(), alice.getGenerator());\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\n// OK\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\nComputes the shared secret using otherPublicKey as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using the specified inputEncoding, and secret is\nencoded using specified outputEncoding.\nIf the inputEncoding is not\nprovided, otherPublicKey is expected to be a Buffer,\nTypedArray, or DataView.
If outputEncoding is given a string is returned; otherwise, a\nBuffer is returned.
Generates private and public Diffie-Hellman key values, and returns\nthe public key in the specified encoding. This key should be\ntransferred to the other party.\nIf encoding is provided a string is returned; otherwise a\nBuffer is returned.
Returns the Diffie-Hellman generator in the specified encoding.\nIf encoding is provided a string is\nreturned; otherwise a Buffer is returned.
Returns the Diffie-Hellman prime in the specified encoding.\nIf encoding is provided a string is\nreturned; otherwise a Buffer is returned.
Returns the Diffie-Hellman private key in the specified encoding.\nIf encoding is provided a\nstring is returned; otherwise a Buffer is returned.
Returns the Diffie-Hellman public key in the specified encoding.\nIf encoding is provided a\nstring is returned; otherwise a Buffer is returned.
Sets the Diffie-Hellman private key. If the encoding argument is provided,\nprivateKey is expected\nto be a string. If no encoding is provided, privateKey is expected\nto be a Buffer, TypedArray, or DataView.
Sets the Diffie-Hellman public key. If the encoding argument is provided,\npublicKey is expected\nto be a string. If no encoding is provided, publicKey is expected\nto be a Buffer, TypedArray, or DataView.
A bit field containing any warnings and/or errors resulting from a check\nperformed during initialization of the DiffieHellman object.
The following values are valid for this property (as defined in constants\nmodule):
DH_CHECK_P_NOT_SAFE_PRIMEDH_CHECK_P_NOT_PRIMEDH_UNABLE_TO_CHECK_GENERATORDH_NOT_SUITABLE_GENERATORThe ECDH class is a utility for creating Elliptic Curve Diffie-Hellman (ECDH)\nkey exchanges.
Instances of the ECDH class can be created using the\ncrypto.createECDH() function.
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createECDH('secp521r1');\nconst aliceKey = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.createECDH('secp521r1');\nconst bobKey = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst aliceSecret = alice.computeSecret(bobKey);\nconst bobSecret = bob.computeSecret(aliceKey);\n\nassert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));\n// OK\nConverts the EC Diffie-Hellman public key specified by key and curve to the\nformat specified by format. The format argument specifies point encoding\nand can be 'compressed', 'uncompressed' or 'hybrid'. The supplied key is\ninterpreted using the specified inputEncoding, and the returned key is encoded\nusing the specified outputEncoding.
Use crypto.getCurves() to obtain a list of available curve names.\nOn recent OpenSSL releases, openssl ecparam -list_curves will also display\nthe name and description of each available elliptic curve.
If format is not specified the point will be returned in 'uncompressed'\nformat.
If the inputEncoding is not provided, key is expected to be a Buffer,\nTypedArray, or DataView.
Example (uncompressing a key):
\nconst { createECDH, ECDH } = require('crypto');\n\nconst ecdh = createECDH('secp256k1');\necdh.generateKeys();\n\nconst compressedKey = ecdh.getPublicKey('hex', 'compressed');\n\nconst uncompressedKey = ECDH.convertKey(compressedKey,\n 'secp256k1',\n 'hex',\n 'hex',\n 'uncompressed');\n\n// the converted key and the uncompressed public key should be the same\nconsole.log(uncompressedKey === ecdh.getPublicKey('hex'));\nComputes the shared secret using otherPublicKey as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using specified inputEncoding, and the returned secret\nis encoded using the specified outputEncoding.\nIf the inputEncoding is not\nprovided, otherPublicKey is expected to be a Buffer, TypedArray, or\nDataView.
If outputEncoding is given a string will be returned; otherwise a\nBuffer is returned.
ecdh.computeSecret will throw an\nERR_CRYPTO_ECDH_INVALID_PUBLIC_KEY error when otherPublicKey\nlies outside of the elliptic curve. Since otherPublicKey is\nusually supplied from a remote user over an insecure network,\nits recommended for developers to handle this exception accordingly.
Generates private and public EC Diffie-Hellman key values, and returns\nthe public key in the specified format and encoding. This key should be\ntransferred to the other party.
The format argument specifies point encoding and can be 'compressed' or\n'uncompressed'. If format is not specified, the point will be returned in\n'uncompressed' format.
If encoding is provided a string is returned; otherwise a Buffer\nis returned.
If encoding is specified, a string is returned; otherwise a Buffer is\nreturned.
The format argument specifies point encoding and can be 'compressed' or\n'uncompressed'. If format is not specified the point will be returned in\n'uncompressed' format.
If encoding is specified, a string is returned; otherwise a Buffer is\nreturned.
Sets the EC Diffie-Hellman private key.\nIf encoding is provided, privateKey is expected\nto be a string; otherwise privateKey is expected to be a Buffer,\nTypedArray, or DataView.
If privateKey is not valid for the curve specified when the ECDH object was\ncreated, an error is thrown. Upon setting the private key, the associated\npublic point (key) is also generated and set in the ECDH object.
Sets the EC Diffie-Hellman public key.\nIf encoding is provided publicKey is expected to\nbe a string; otherwise a Buffer, TypedArray, or DataView is expected.
Note that there is not normally a reason to call this method because ECDH\nonly requires a private key and the other party's public key to compute the\nshared secret. Typically either ecdh.generateKeys() or\necdh.setPrivateKey() will be called. The ecdh.setPrivateKey() method\nattempts to generate the public point/key associated with the private key being\nset.
Example (obtaining a shared secret):
\nconst crypto = require('crypto');\nconst alice = crypto.createECDH('secp256k1');\nconst bob = crypto.createECDH('secp256k1');\n\n// This is a shortcut way of specifying one of Alice's previous private\n// keys. It would be unwise to use such a predictable private key in a real\n// application.\nalice.setPrivateKey(\n crypto.createHash('sha256').update('alice', 'utf8').digest()\n);\n\n// Bob uses a newly generated cryptographically strong\n// pseudorandom key pair\nbob.generateKeys();\n\nconst aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n// aliceSecret and bobSecret should be the same shared secret value\nconsole.log(aliceSecret === bobSecret);\nThe Hash class is a utility for creating hash digests of data. It can be\nused in one of two ways:
hash.update() and hash.digest() methods to produce the\ncomputed hash.The crypto.createHash() method is used to create Hash instances. Hash\nobjects are not to be created directly using the new keyword.
Example: Using Hash objects as streams:
const crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hash.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n }\n});\n\nhash.write('some data to hash');\nhash.end();\nExample: Using Hash and piped streams:
const crypto = require('crypto');\nconst fs = require('fs');\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hash).pipe(process.stdout);\nExample: Using the hash.update() and hash.digest() methods:
const crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.update('some data to hash');\nconsole.log(hash.digest('hex'));\n// Prints:\n// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\nCalculates the digest of all of the data passed to be hashed (using the\nhash.update() method).\nIf encoding is provided a string will be returned; otherwise\na Buffer is returned.
The Hash object can not be used again after hash.digest() method has been\ncalled. Multiple calls will cause an error to be thrown.
Updates the hash content with the given data, the encoding of which\nis given in inputEncoding.\nIf encoding is not provided, and the data is a string, an\nencoding of 'utf8' is enforced. If data is a Buffer, TypedArray, or\nDataView, then inputEncoding is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: Hmac", "type": "class", "name": "Hmac", "meta": { "added": [ "v0.1.94" ], "changes": [] }, "desc": "The Hmac Class is a utility for creating cryptographic HMAC digests. It can\nbe used in one of two ways:
hmac.update() and hmac.digest() methods to produce the\ncomputed HMAC digest.The crypto.createHmac() method is used to create Hmac instances. Hmac\nobjects are not to be created directly using the new keyword.
Example: Using Hmac objects as streams:
const crypto = require('crypto');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nhmac.on('readable', () => {\n // Only one element is going to be produced by the\n // hash stream.\n const data = hmac.read();\n if (data) {\n console.log(data.toString('hex'));\n // Prints:\n // 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n }\n});\n\nhmac.write('some data to hash');\nhmac.end();\nExample: Using Hmac and piped streams:
const crypto = require('crypto');\nconst fs = require('fs');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hmac).pipe(process.stdout);\nExample: Using the hmac.update() and hmac.digest() methods:
const crypto = require('crypto');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nhmac.update('some data to hash');\nconsole.log(hmac.digest('hex'));\n// Prints:\n// 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\nCalculates the HMAC digest of all of the data passed using hmac.update().\nIf encoding is\nprovided a string is returned; otherwise a Buffer is returned;
The Hmac object can not be used again after hmac.digest() has been\ncalled. Multiple calls to hmac.digest() will result in an error being thrown.
Updates the Hmac content with the given data, the encoding of which\nis given in inputEncoding.\nIf encoding is not provided, and the data is a string, an\nencoding of 'utf8' is enforced. If data is a Buffer, TypedArray, or\nDataView, then inputEncoding is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: Sign", "type": "class", "name": "Sign", "meta": { "added": [ "v0.1.92" ], "changes": [] }, "desc": "The Sign Class is a utility for generating signatures. It can be used in one\nof two ways:
sign.sign() method is used to generate and return the signature, orsign.update() and sign.sign() methods to produce the\nsignature.The crypto.createSign() method is used to create Sign instances. The\nargument is the string name of the hash function to use. Sign objects are not\nto be created directly using the new keyword.
Example: Using Sign objects as streams:
const crypto = require('crypto');\nconst sign = crypto.createSign('SHA256');\n\nsign.write('some data to sign');\nsign.end();\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature using the specified private key and\n// SHA-256. For RSA keys, the algorithm is RSASSA-PKCS1-v1_5 (see padding\n// parameter below for RSASSA-PSS). For EC keys, the algorithm is ECDSA.\nExample: Using the sign.update() and sign.sign() methods:
const crypto = require('crypto');\nconst sign = crypto.createSign('SHA256');\n\nsign.update('some data to sign');\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature\nIn some cases, a Sign instance can also be created by passing in a signature\nalgorithm name, such as 'RSA-SHA256'. This will use the corresponding digest\nalgorithm. This does not work for all signature algorithms, such as\n'ecdsa-with-SHA256'. Use digest names instead.
Example: signing using legacy signature algorithm name
\nconst crypto = require('crypto');\nconst sign = crypto.createSign('RSA-SHA256');\n\nsign.update('some data to sign');\n\nconst privateKey = getPrivateKeySomehow();\nconsole.log(sign.sign(privateKey, 'hex'));\n// Prints: the calculated signature\nCalculates the signature on all the data passed through using either\nsign.update() or sign.write().
The privateKey argument can be an object or a string. If privateKey is a\nstring, it is treated as a raw key with no passphrase. If privateKey is an\nobject, it must contain one or more of the following properties:
key: <string> - PEM encoded private key (required)
passphrase: <string> - passphrase for the private key
padding: <integer> - Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING (default)crypto.constants.RSA_PKCS1_PSS_PADDINGNote that RSA_PKCS1_PSS_PADDING will use MGF1 with the same hash function\nused to sign the message as specified in section 3.1 of RFC 4055.
saltLength: <integer> - salt length for when padding is\nRSA_PKCS1_PSS_PADDING. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN (default) sets it to the\nmaximum permissible value.
If outputEncoding is provided a string is returned; otherwise a Buffer\nis returned.
The Sign object can not be again used after sign.sign() method has been\ncalled. Multiple calls to sign.sign() will result in an error being thrown.
Updates the Sign content with the given data, the encoding of which\nis given in inputEncoding.\nIf encoding is not provided, and the data is a string, an\nencoding of 'utf8' is enforced. If data is a Buffer, TypedArray, or\nDataView, then inputEncoding is ignored.
This can be called many times with new data as it is streamed.
" } ] }, { "textRaw": "Class: Verify", "type": "class", "name": "Verify", "meta": { "added": [ "v0.1.92" ], "changes": [] }, "desc": "The Verify class is a utility for verifying signatures. It can be used in one\nof two ways:
verify.update() and verify.verify() methods to verify\nthe signature.The crypto.createVerify() method is used to create Verify instances.\nVerify objects are not to be created directly using the new keyword.
Example: Using Verify objects as streams:
const crypto = require('crypto');\nconst verify = crypto.createVerify('SHA256');\n\nverify.write('some data to sign');\nverify.end();\n\nconst publicKey = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true or false\nExample: Using the verify.update() and verify.verify() methods:
const crypto = require('crypto');\nconst verify = crypto.createVerify('SHA256');\n\nverify.update('some data to sign');\n\nconst publicKey = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(verify.verify(publicKey, signature));\n// Prints: true or false\nUpdates the Verify content with the given data, the encoding of which\nis given in inputEncoding.\nIf inputEncoding is not provided, and the data is a string, an\nencoding of 'utf8' is enforced. If data is a Buffer, TypedArray, or\nDataView, then inputEncoding is ignored.
This can be called many times with new data as it is streamed.
" }, { "textRaw": "verify.verify(object, signature[, signatureEncoding])", "type": "method", "name": "verify", "meta": { "added": [ "v0.1.92" ], "changes": [ { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11705", "description": "Support for RSASSA-PSS and additional options was added." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean} `true` or `false` depending on the validity of the signature for the data and public key.", "name": "return", "type": "boolean", "desc": "`true` or `false` depending on the validity of the signature for the data and public key." }, "params": [ { "textRaw": "`object` {string | Object}", "name": "object", "type": "string | Object" }, { "textRaw": "`signature` {string | Buffer | TypedArray | DataView}", "name": "signature", "type": "string | Buffer | TypedArray | DataView" }, { "textRaw": "`signatureEncoding` {string} The [encoding][] of the `signature` string.", "name": "signatureEncoding", "type": "string", "desc": "The [encoding][] of the `signature` string.", "optional": true } ] } ], "desc": "Verifies the provided data using the given object and signature.\nThe object argument can be either a string containing a PEM encoded object,\nwhich can be an RSA public key, a DSA public key, or an X.509 certificate,\nor an object with one or more of the following properties:
key: <string> - PEM encoded public key (required)
padding: <integer> - Optional padding value for RSA, one of the following:
crypto.constants.RSA_PKCS1_PADDING (default)crypto.constants.RSA_PKCS1_PSS_PADDINGNote that RSA_PKCS1_PSS_PADDING will use MGF1 with the same hash function\nused to verify the message as specified in section 3.1 of RFC 4055.
saltLength: <integer> - salt length for when padding is\nRSA_PKCS1_PSS_PADDING. The special value\ncrypto.constants.RSA_PSS_SALTLEN_DIGEST sets the salt length to the digest\nsize, crypto.constants.RSA_PSS_SALTLEN_AUTO (default) causes it to be\ndetermined automatically.
The signature argument is the previously calculated signature for the data, in\nthe signatureEncoding.\nIf a signatureEncoding is specified, the signature is expected to be a\nstring; otherwise signature is expected to be a Buffer,\nTypedArray, or DataView.
The verify object can not be used again after verify.verify() has been\ncalled. Multiple calls to verify.verify() will result in an error being\nthrown.
The dns module contains functions belonging to two different categories:
1) Functions that use the underlying operating system facilities to perform\nname resolution, and that do not necessarily perform any network communication.\nThis category contains only one function: dns.lookup(). Developers\nlooking to perform name resolution in the same way that other applications on\nthe same operating system behave should use dns.lookup().
For example, looking up iana.org.
const dns = require('dns');\n\ndns.lookup('iana.org', (err, address, family) => {\n console.log('address: %j family: IPv%s', address, family);\n});\n// address: \"192.0.43.8\" family: IPv4\n2) Functions that connect to an actual DNS server to perform name resolution,\nand that always use the network to perform DNS queries. This category\ncontains all functions in the dns module except dns.lookup(). These\nfunctions do not use the same set of configuration files used by\ndns.lookup() (e.g. /etc/hosts). These functions should be used by\ndevelopers who do not want to use the underlying operating system's facilities\nfor name resolution, and instead want to always perform DNS queries.
Below is an example that resolves 'archive.org' then reverse resolves the IP\naddresses that are returned.
const dns = require('dns');\n\ndns.resolve4('archive.org', (err, addresses) => {\n if (err) throw err;\n\n console.log(`addresses: ${JSON.stringify(addresses)}`);\n\n addresses.forEach((a) => {\n dns.reverse(a, (err, hostnames) => {\n if (err) {\n throw err;\n }\n console.log(`reverse for ${a}: ${JSON.stringify(hostnames)}`);\n });\n });\n});\nThere are subtle consequences in choosing one over the other, please consult\nthe Implementation considerations section for more information.
", "modules": [ { "textRaw": "Class: `dns.Resolver`", "name": "class:_`dns.resolver`", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "desc": "An independent resolver for DNS requests.
\nNote that creating a new resolver uses the default server settings. Setting\nthe servers used for a resolver using\nresolver.setServers() does not affect\nother resolvers:
const { Resolver } = require('dns');\nconst resolver = new Resolver();\nresolver.setServers(['4.4.4.4']);\n\n// This request will use the server at 4.4.4.4, independent of global settings.\nresolver.resolve4('example.org', (err, addresses) => {\n // ...\n});\nThe following methods from the dns module are available:
resolver.getServers()resolver.resolve()resolver.resolve4()resolver.resolve6()resolver.resolveAny()resolver.resolveCname()resolver.resolveMx()resolver.resolveNaptr()resolver.resolveNs()resolver.resolvePtr()resolver.resolveSoa()resolver.resolveSrv()resolver.resolveTxt()resolver.reverse()resolver.setServers()Cancel all outstanding DNS queries made by this resolver. The corresponding\ncallbacks will be called with an error with code ECANCELLED.
Returns an array of IP address strings, formatted according to rfc5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '4.4.4.4',\n '2001:4860:4860::8888',\n '4.4.4.4:1053',\n '[2001:4860:4860::8888]:1053'\n]\nhostname <string>family <integer> The record family. Must be 4 or 6. IPv4\nand IPv6 addresses are both returned by default.hints <number> One or more supported getaddrinfo flags. Multiple\nflags may be passed by bitwise ORing their values.all <boolean> When true, the callback returns all resolved addresses in\nan array. Otherwise, returns a single address. Default: false.verbatim <boolean> When true, the callback receives IPv4 and IPv6\naddresses in the order the DNS resolver returned them. When false,\nIPv4 addresses are placed before IPv6 addresses.\nDefault: currently false (addresses are reordered) but this is\nexpected to change in the not too distant future.\nNew code should use { verbatim: true }.callback <Function>
Resolves a hostname (e.g. 'nodejs.org') into the first found A (IPv4) or\nAAAA (IPv6) record. All option properties are optional. If options is an\ninteger, then it must be 4 or 6 – if options is not provided, then IPv4\nand IPv6 addresses are both returned if found.
With the all option set to true, the arguments for callback change to\n(err, addresses), with addresses being an array of objects with the\nproperties address and family.
On error, err is an Error object, where err.code is the error code.\nKeep in mind that err.code will be set to 'ENOENT' not only when\nthe hostname does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.
dns.lookup() does not necessarily have anything to do with the DNS protocol.\nThe implementation uses an operating system facility that can associate names\nwith addresses, and vice versa. This implementation can have subtle but\nimportant consequences on the behavior of any Node.js program. Please take some\ntime to consult the Implementation considerations section before using\ndns.lookup().
Example usage:
\nconst dns = require('dns');\nconst options = {\n family: 6,\n hints: dns.ADDRCONFIG | dns.V4MAPPED,\n};\ndns.lookup('example.com', options, (err, address, family) =>\n console.log('address: %j family: IPv%s', address, family));\n// address: \"2606:2800:220:1:248:1893:25c8:1946\" family: IPv6\n\n// When options.all is true, the result will be an Array.\noptions.all = true;\ndns.lookup('example.com', options, (err, addresses) =>\n console.log('addresses: %j', addresses));\n// addresses: [{\"address\":\"2606:2800:220:1:248:1893:25c8:1946\",\"family\":6}]\nIf this method is invoked as its util.promisify()ed version, and all\nis not set to true, it returns a Promise for an Object with address and\nfamily properties.
The following flags can be passed as hints to dns.lookup().
dns.ADDRCONFIG: Returned address types are determined by the types\nof addresses supported by the current system. For example, IPv4 addresses\nare only returned if the current system has at least one IPv4 address\nconfigured. Loopback addresses are not considered.dns.V4MAPPED: If the IPv6 family was specified, but no IPv6 addresses were\nfound, then return IPv4 mapped IPv6 addresses. Note that it is not supported\non some operating systems (e.g FreeBSD 10.1).address <string>port <number>callback <Function>
Resolves the given address and port into a hostname and service using\nthe operating system's underlying getnameinfo implementation.
If address is not a valid IP address, a TypeError will be thrown.\nThe port will be coerced to a number. If it is not a legal port, a TypeError\nwill be thrown.
On an error, err is an Error object, where err.code is the error code.
const dns = require('dns');\ndns.lookupService('127.0.0.1', 22, (err, hostname, service) => {\n console.log(hostname, service);\n // Prints: localhost ssh\n});\nIf this method is invoked as its util.promisify()ed version, it returns a\nPromise for an Object with hostname and service properties.
hostname <string> Hostname to resolve.rrtype <string> Resource record type. Default: 'A'.callback <Function>
err <Error>records <string[]> | <Object[]> | <Object>Uses the DNS protocol to resolve a hostname (e.g. 'nodejs.org') into an array\nof the resource records. The callback function has arguments\n(err, records). When successful, records will be an array of resource\nrecords. The type and structure of individual results varies based on rrtype:
rrtype | \nrecords contains | \nResult type | \nShorthand method | \n
|---|---|---|---|
'A' | \nIPv4 addresses (default) | \n<string> | \ndns.resolve4() | \n
'AAAA' | \nIPv6 addresses | \n<string> | \ndns.resolve6() | \n
'ANY' | \nany records | \n<Object> | \ndns.resolveAny() | \n
'CNAME' | \ncanonical name records | \n<string> | \ndns.resolveCname() | \n
'MX' | \nmail exchange records | \n<Object> | \ndns.resolveMx() | \n
'NAPTR' | \nname authority pointer records | \n<Object> | \ndns.resolveNaptr() | \n
'NS' | \nname server records | \n<string> | \ndns.resolveNs() | \n
'PTR' | \npointer records | \n<string> | \ndns.resolvePtr() | \n
'SOA' | \nstart of authority records | \n<Object> | \ndns.resolveSoa() | \n
'SRV' | \nservice records | \n<Object> | \ndns.resolveSrv() | \n
'TXT' | \ntext records | \n<string[]> | \ndns.resolveTxt() | \n
On error, err is an Error object, where err.code is one of the\nDNS error codes.
hostname <string> Hostname to resolve.options <Object>
ttl <boolean> Retrieve the Time-To-Live value (TTL) of each record.\nWhen true, the callback receives an array of\n{ address: '1.2.3.4', ttl: 60 } objects rather than an array of strings,\nwith the TTL expressed in seconds.callback <Function>
err <Error>addresses <string[]> | <Object[]>Uses the DNS protocol to resolve a IPv4 addresses (A records) for the\nhostname. The addresses argument passed to the callback function\nwill contain an array of IPv4 addresses (e.g.\n['74.125.79.104', '74.125.79.105', '74.125.79.106']).
hostname <string> Hostname to resolve.options <Object>
ttl <boolean> Retrieve the Time-To-Live value (TTL) of each record.\nWhen true, the callback receives an array of\n{ address: '0:1:2:3:4:5:6:7', ttl: 60 } objects rather than an array of\nstrings, with the TTL expressed in seconds.callback <Function>
err <Error>addresses <string[]> | <Object[]>Uses the DNS protocol to resolve a IPv6 addresses (AAAA records) for the\nhostname. The addresses argument passed to the callback function\nwill contain an array of IPv6 addresses.
hostname <string>callback <Function>
err <Error>ret <Object[]>Uses the DNS protocol to resolve all records (also known as ANY or * query).\nThe ret argument passed to the callback function will be an array containing\nvarious types of records. Each object has a property type that indicates the\ntype of the current record. And depending on the type, additional properties\nwill be present on the object:
| Type | \nProperties | \n
|---|---|
'A' | \naddress/ttl | \n
'AAAA' | \naddress/ttl | \n
'CNAME' | \nvalue | \n
'MX' | \nRefer to dns.resolveMx() | \n
'NAPTR' | \nRefer to dns.resolveNaptr() | \n
'NS' | \nvalue | \n
'PTR' | \nvalue | \n
'SOA' | \nRefer to dns.resolveSoa() | \n
'SRV' | \nRefer to dns.resolveSrv() | \n
'TXT' | \nThis type of record contains an array property called entries which refers to dns.resolveTxt(), e.g. { entries: ['...'], type: 'TXT' } | \n
Here is an example of the ret object passed to the callback:
[ { type: 'A', address: '127.0.0.1', ttl: 299 },\n { type: 'CNAME', value: 'example.com' },\n { type: 'MX', exchange: 'alt4.aspmx.l.example.com', priority: 50 },\n { type: 'NS', value: 'ns1.example.com' },\n { type: 'TXT', entries: [ 'v=spf1 include:_spf.example.com ~all' ] },\n { type: 'SOA',\n nsname: 'ns1.example.com',\n hostmaster: 'admin.example.com',\n serial: 156696742,\n refresh: 900,\n retry: 900,\n expire: 1800,\n minttl: 60 } ]\nDNS server operators may choose not to respond to ANY\nqueries. It may be better to call individual methods like dns.resolve4(),\ndns.resolveMx(), and so on. For more details, see RFC 8482.
hostname <string>callback <Function>
err <Error>addresses <string[]>Uses the DNS protocol to resolve CNAME records for the hostname. The\naddresses argument passed to the callback function\nwill contain an array of canonical name records available for the hostname\n(e.g. ['bar.example.com']).
hostname <string>callback <Function>
err <Error>addresses <Object[]>Uses the DNS protocol to resolve mail exchange records (MX records) for the\nhostname. The addresses argument passed to the callback function will\ncontain an array of objects containing both a priority and exchange\nproperty (e.g. [{priority: 10, exchange: 'mx.example.com'}, ...]).
hostname <string>callback <Function>
err <Error>addresses <Object[]>Uses the DNS protocol to resolve regular expression based records (NAPTR\nrecords) for the hostname. The addresses argument passed to the callback\nfunction will contain an array of objects with the following properties:
flagsserviceregexpreplacementorderpreference{\n flags: 's',\n service: 'SIP+D2U',\n regexp: '',\n replacement: '_sip._udp.example.com',\n order: 30,\n preference: 100\n}\nhostname <string>callback <Function>
err <Error>addresses <string[]>Uses the DNS protocol to resolve name server records (NS records) for the\nhostname. The addresses argument passed to the callback function will\ncontain an array of name server records available for hostname\n(e.g. ['ns1.example.com', 'ns2.example.com']).
hostname <string>callback <Function>
err <Error>addresses <string[]>Uses the DNS protocol to resolve pointer records (PTR records) for the\nhostname. The addresses argument passed to the callback function will\nbe an array of strings containing the reply records.
hostname <string>callback <Function>
Uses the DNS protocol to resolve a start of authority record (SOA record) for\nthe hostname. The address argument passed to the callback function will\nbe an object with the following properties:
nsnamehostmasterserialrefreshretryexpireminttl{\n nsname: 'ns.example.com',\n hostmaster: 'root.example.com',\n serial: 2013101809,\n refresh: 10000,\n retry: 2400,\n expire: 604800,\n minttl: 3600\n}\nhostname <string>callback <Function>
err <Error>addresses <Object[]>Uses the DNS protocol to resolve service records (SRV records) for the\nhostname. The addresses argument passed to the callback function will\nbe an array of objects with the following properties:
priorityweightportname{\n priority: 10,\n weight: 5,\n port: 21223,\n name: 'service.example.com'\n}\nhostname <string>callback <Function>
err <Error>records {string[][]}Uses the DNS protocol to resolve text queries (TXT records) for the\nhostname. The records argument passed to the callback function is a\ntwo-dimensional array of the text records available for hostname (e.g.\n[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]). Each sub-array contains TXT chunks of\none record. Depending on the use case, these could be either joined together or\ntreated separately.
ip <string>callback <Function>
err <Error>hostnames <string[]>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an\narray of hostnames.
\nOn error, err is an Error object, where err.code is\none of the DNS error codes.
servers <string[]> array of rfc5952 formatted addressesSets the IP address and port of servers to be used when performing DNS\nresolution. The servers argument is an array of rfc5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dns.setServers([\n '4.4.4.4',\n '[2001:4860:4860::8888]',\n '4.4.4.4:1053',\n '[2001:4860:4860::8888]:1053'\n]);\nAn error will be thrown if an invalid address is provided.
\nThe dns.setServers() method must not be called while a DNS query is in\nprogress.
The dns.setServers() method affects only dns.resolve(),\n[dns.resolve*()][] and dns.reverse() (and specifically not\ndns.lookup()).
Note that this method works much like\nresolve.conf.\nThat is, if attempting to resolve with the first server provided results in a\nNOTFOUND error, the resolve() method will not attempt to resolve with\nsubsequent servers provided. Fallback DNS servers will only be used if the\nearlier ones time out or result in some other error.
The dns.promises API provides an alternative set of asynchronous DNS methods\nthat return Promise objects rather than using callbacks. The API is accessible\nvia require('dns').promises.
An independent resolver for DNS requests.
\nNote that creating a new resolver uses the default server settings. Setting\nthe servers used for a resolver using\nresolver.setServers() does not affect\nother resolvers:
const { Resolver } = require('dns').promises;\nconst resolver = new Resolver();\nresolver.setServers(['4.4.4.4']);\n\n// This request will use the server at 4.4.4.4, independent of global settings.\nresolver.resolve4('example.org').then((addresses) => {\n // ...\n});\n\n// Alternatively, the same code can be written using async-await style.\n(async function() {\n const addresses = await resolver.resolve4('example.org');\n})();\nThe following methods from the dnsPromises API are available:
resolver.getServers()resolver.resolve()resolver.resolve4()resolver.resolve6()resolver.resolveAny()resolver.resolveCname()resolver.resolveMx()resolver.resolveNaptr()resolver.resolveNs()resolver.resolvePtr()resolver.resolveSoa()resolver.resolveSrv()resolver.resolveTxt()resolver.reverse()resolver.setServers()Returns an array of IP address strings, formatted according to rfc5952,\nthat are currently configured for DNS resolution. A string will include a port\nsection if a custom port is used.
\n\n[\n '4.4.4.4',\n '2001:4860:4860::8888',\n '4.4.4.4:1053',\n '[2001:4860:4860::8888]:1053'\n]\nhostname <string>family <integer> The record family. Must be 4 or 6. IPv4\nand IPv6 addresses are both returned by default.hints <number> One or more supported getaddrinfo flags. Multiple\nflags may be passed by bitwise ORing their values.all <boolean> When true, the Promise is resolved with all addresses in\nan array. Otherwise, returns a single address. Default: false.verbatim <boolean> When true, the Promise is resolved with IPv4 and\nIPv6 addresses in the order the DNS resolver returned them. When false,\nIPv4 addresses are placed before IPv6 addresses.\nDefault: currently false (addresses are reordered) but this is\nexpected to change in the not too distant future.\nNew code should use { verbatim: true }.Resolves a hostname (e.g. 'nodejs.org') into the first found A (IPv4) or\nAAAA (IPv6) record. All option properties are optional. If options is an\ninteger, then it must be 4 or 6 – if options is not provided, then IPv4\nand IPv6 addresses are both returned if found.
With the all option set to true, the Promise is resolved with addresses\nbeing an array of objects with the properties address and family.
On error, the Promise is rejected with an Error object, where err.code\nis the error code.\nKeep in mind that err.code will be set to 'ENOENT' not only when\nthe hostname does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.
dnsPromises.lookup() does not necessarily have anything to do with the DNS\nprotocol. The implementation uses an operating system facility that can\nassociate names with addresses, and vice versa. This implementation can have\nsubtle but important consequences on the behavior of any Node.js program. Please\ntake some time to consult the Implementation considerations section before\nusing dnsPromises.lookup().
Example usage:
\nconst dns = require('dns');\nconst dnsPromises = dns.promises;\nconst options = {\n family: 6,\n hints: dns.ADDRCONFIG | dns.V4MAPPED,\n};\n\ndnsPromises.lookup('example.com', options).then((result) => {\n console.log('address: %j family: IPv%s', result.address, result.family);\n // address: \"2606:2800:220:1:248:1893:25c8:1946\" family: IPv6\n});\n\n// When options.all is true, the result will be an Array.\noptions.all = true;\ndnsPromises.lookup('example.com', options).then((result) => {\n console.log('addresses: %j', result);\n // addresses: [{\"address\":\"2606:2800:220:1:248:1893:25c8:1946\",\"family\":6}]\n});\nResolves the given address and port into a hostname and service using\nthe operating system's underlying getnameinfo implementation.
If address is not a valid IP address, a TypeError will be thrown.\nThe port will be coerced to a number. If it is not a legal port, a TypeError\nwill be thrown.
On error, the Promise is rejected with an Error object, where err.code\nis the error code.
const dnsPromises = require('dns').promises;\ndnsPromises.lookupService('127.0.0.1', 22).then((result) => {\n console.log(result.hostname, result.service);\n // Prints: localhost ssh\n});\nUses the DNS protocol to resolve a hostname (e.g. 'nodejs.org') into an array\nof the resource records. When successful, the Promise is resolved with an\narray of resource records. The type and structure of individual results vary\nbased on rrtype:
rrtype | \nrecords contains | \nResult type | \nShorthand method | \n
|---|---|---|---|
'A' | \nIPv4 addresses (default) | \n<string> | \ndnsPromises.resolve4() | \n
'AAAA' | \nIPv6 addresses | \n<string> | \ndnsPromises.resolve6() | \n
'ANY' | \nany records | \n<Object> | \ndnsPromises.resolveAny() | \n
'CNAME' | \ncanonical name records | \n<string> | \ndnsPromises.resolveCname() | \n
'MX' | \nmail exchange records | \n<Object> | \ndnsPromises.resolveMx() | \n
'NAPTR' | \nname authority pointer records | \n<Object> | \ndnsPromises.resolveNaptr() | \n
'NS' | \nname server records | \n<string> | \ndnsPromises.resolveNs() | \n
'PTR' | \npointer records | \n<string> | \ndnsPromises.resolvePtr() | \n
'SOA' | \nstart of authority records | \n<Object> | \ndnsPromises.resolveSoa() | \n
'SRV' | \nservice records | \n<Object> | \ndnsPromises.resolveSrv() | \n
'TXT' | \ntext records | \n<string[]> | \ndnsPromises.resolveTxt() | \n
On error, the Promise is rejected with an Error object, where err.code\nis one of the DNS error codes.
hostname <string> Hostname to resolve.options <Object>
ttl <boolean> Retrieve the Time-To-Live value (TTL) of each record.\nWhen true, the Promise is resolved with an array of\n{ address: '1.2.3.4', ttl: 60 } objects rather than an array of strings,\nwith the TTL expressed in seconds.Uses the DNS protocol to resolve IPv4 addresses (A records) for the\nhostname. On success, the Promise is resolved with an array of IPv4\naddresses (e.g. ['74.125.79.104', '74.125.79.105', '74.125.79.106']).
hostname <string> Hostname to resolve.options <Object>
ttl <boolean> Retrieve the Time-To-Live value (TTL) of each record.\nWhen true, the Promise is resolved with an array of\n{ address: '0:1:2:3:4:5:6:7', ttl: 60 } objects rather than an array of\nstrings, with the TTL expressed in seconds.Uses the DNS protocol to resolve IPv6 addresses (AAAA records) for the\nhostname. On success, the Promise is resolved with an array of IPv6\naddresses.
hostname <string>Uses the DNS protocol to resolve all records (also known as ANY or * query).\nOn success, the Promise is resolved with an array containing various types of\nrecords. Each object has a property type that indicates the type of the\ncurrent record. And depending on the type, additional properties will be\npresent on the object:
| Type | \nProperties | \n
|---|---|
'A' | \naddress/ttl | \n
'AAAA' | \naddress/ttl | \n
'CNAME' | \nvalue | \n
'MX' | \nRefer to dnsPromises.resolveMx() | \n
'NAPTR' | \nRefer to dnsPromises.resolveNaptr() | \n
'NS' | \nvalue | \n
'PTR' | \nvalue | \n
'SOA' | \nRefer to dnsPromises.resolveSoa() | \n
'SRV' | \nRefer to dnsPromises.resolveSrv() | \n
'TXT' | \nThis type of record contains an array property called entries which refers to dnsPromises.resolveTxt(), e.g. { entries: ['...'], type: 'TXT' } | \n
Here is an example of the result object:
\n\n[ { type: 'A', address: '127.0.0.1', ttl: 299 },\n { type: 'CNAME', value: 'example.com' },\n { type: 'MX', exchange: 'alt4.aspmx.l.example.com', priority: 50 },\n { type: 'NS', value: 'ns1.example.com' },\n { type: 'TXT', entries: [ 'v=spf1 include:_spf.example.com ~all' ] },\n { type: 'SOA',\n nsname: 'ns1.example.com',\n hostmaster: 'admin.example.com',\n serial: 156696742,\n refresh: 900,\n retry: 900,\n expire: 1800,\n minttl: 60 } ]\nhostname <string>Uses the DNS protocol to resolve CNAME records for the hostname. On success,\nthe Promise is resolved with an array of canonical name records available for\nthe hostname (e.g. ['bar.example.com']).
hostname <string>Uses the DNS protocol to resolve mail exchange records (MX records) for the\nhostname. On success, the Promise is resolved with an array of objects\ncontaining both a priority and exchange property (e.g.\n[{priority: 10, exchange: 'mx.example.com'}, ...]).
hostname <string>Uses the DNS protocol to resolve regular expression based records (NAPTR\nrecords) for the hostname. On success, the Promise is resolved with an array\nof objects with the following properties:
flagsserviceregexpreplacementorderpreference{\n flags: 's',\n service: 'SIP+D2U',\n regexp: '',\n replacement: '_sip._udp.example.com',\n order: 30,\n preference: 100\n}\nhostname <string>Uses the DNS protocol to resolve name server records (NS records) for the\nhostname. On success, the Promise is resolved with an array of name server\nrecords available for hostname (e.g.\n['ns1.example.com', 'ns2.example.com']).
hostname <string>Uses the DNS protocol to resolve pointer records (PTR records) for the\nhostname. On success, the Promise is resolved with an array of strings\ncontaining the reply records.
hostname <string>Uses the DNS protocol to resolve a start of authority record (SOA record) for\nthe hostname. On success, the Promise is resolved with an object with the\nfollowing properties:
nsnamehostmasterserialrefreshretryexpireminttl{\n nsname: 'ns.example.com',\n hostmaster: 'root.example.com',\n serial: 2013101809,\n refresh: 10000,\n retry: 2400,\n expire: 604800,\n minttl: 3600\n}\nhostname <string>Uses the DNS protocol to resolve service records (SRV records) for the\nhostname. On success, the Promise is resolved with an array of objects with\nthe following properties:
priorityweightportname{\n priority: 10,\n weight: 5,\n port: 21223,\n name: 'service.example.com'\n}\nhostname <string>Uses the DNS protocol to resolve text queries (TXT records) for the\nhostname. On success, the Promise is resolved with a two-dimensional array\nof the text records available for hostname (e.g.\n[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]). Each sub-array contains TXT chunks of\none record. Depending on the use case, these could be either joined together or\ntreated separately.
ip <string>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an\narray of hostnames.
\nOn error, the Promise is rejected with an Error object, where err.code\nis one of the DNS error codes.
servers <string[]> array of rfc5952 formatted addressesSets the IP address and port of servers to be used when performing DNS\nresolution. The servers argument is an array of rfc5952 formatted\naddresses. If the port is the IANA default DNS port (53) it can be omitted.
dnsPromises.setServers([\n '4.4.4.4',\n '[2001:4860:4860::8888]',\n '4.4.4.4:1053',\n '[2001:4860:4860::8888]:1053'\n]);\nAn error will be thrown if an invalid address is provided.
\nThe dnsPromises.setServers() method must not be called while a DNS query is in\nprogress.
Note that this method works much like\nresolve.conf.\nThat is, if attempting to resolve with the first server provided results in a\nNOTFOUND error, the resolve() method will not attempt to resolve with\nsubsequent servers provided. Fallback DNS servers will only be used if the\nearlier ones time out or result in some other error.
Each DNS query can return one of the following error codes:
\ndns.NODATA: DNS server returned answer with no data.dns.FORMERR: DNS server claims query was misformatted.dns.SERVFAIL: DNS server returned general failure.dns.NOTFOUND: Domain name not found.dns.NOTIMP: DNS server does not implement requested operation.dns.REFUSED: DNS server refused query.dns.BADQUERY: Misformatted DNS query.dns.BADNAME: Misformatted hostname.dns.BADFAMILY: Unsupported address family.dns.BADRESP: Misformatted DNS reply.dns.CONNREFUSED: Could not contact DNS servers.dns.TIMEOUT: Timeout while contacting DNS servers.dns.EOF: End of file.dns.FILE: Error reading file.dns.NOMEM: Out of memory.dns.DESTRUCTION: Channel is being destroyed.dns.BADSTR: Misformatted string.dns.BADFLAGS: Illegal flags specified.dns.NONAME: Given hostname is not numeric.dns.BADHINTS: Illegal hints flags specified.dns.NOTINITIALIZED: c-ares library initialization not yet performed.dns.LOADIPHLPAPI: Error loading iphlpapi.dll.dns.ADDRGETNETWORKPARAMS: Could not find GetNetworkParams function.dns.CANCELLED: DNS query cancelled.Although dns.lookup() and the various dns.resolve*()/dns.reverse()\nfunctions have the same goal of associating a network name with a network\naddress (or vice versa), their behavior is quite different. These differences\ncan have subtle but significant consequences on the behavior of Node.js\nprograms.
Under the hood, dns.lookup() uses the same operating system facilities\nas most other programs. For instance, dns.lookup() will almost always\nresolve a given name the same way as the ping command. On most POSIX-like\noperating systems, the behavior of the dns.lookup() function can be\nmodified by changing settings in nsswitch.conf(5) and/or resolv.conf(5),\nbut note that changing these files will change the behavior of all other\nprograms running on the same operating system.
Though the call to dns.lookup() will be asynchronous from JavaScript's\nperspective, it is implemented as a synchronous call to getaddrinfo(3) that runs\non libuv's threadpool. This can have surprising negative performance\nimplications for some applications, see the UV_THREADPOOL_SIZE\ndocumentation for more information.
Note that various networking APIs will call dns.lookup() internally to resolve\nhost names. If that is an issue, consider resolving the hostname to an address\nusing dns.resolve() and using the address instead of a host name. Also, some\nnetworking APIs (such as socket.connect() and dgram.createSocket())\nallow the default resolver, dns.lookup(), to be replaced.
These functions are implemented quite differently than dns.lookup(). They\ndo not use getaddrinfo(3) and they always perform a DNS query on the\nnetwork. This network communication is always done asynchronously, and does not\nuse libuv's threadpool.
As a result, these functions cannot have the same negative impact on other\nprocessing that happens on libuv's threadpool that dns.lookup() can have.
They do not use the same set of configuration files than what dns.lookup()\nuses. For instance, they do not use the configuration from /etc/hosts.
This module is pending deprecation. Once a replacement API has been\nfinalized, this module will be fully deprecated. Most end users should\nnot have cause to use this module. Users who absolutely must have\nthe functionality that domains provide may rely on it for the time being\nbut should expect to have to migrate to a different solution\nin the future.
\nDomains provide a way to handle multiple different IO operations as a\nsingle group. If any of the event emitters or callbacks registered to a\ndomain emit an 'error' event, or throw an error, then the domain object\nwill be notified, rather than losing the context of the error in the\nprocess.on('uncaughtException') handler, or causing the program to\nexit immediately with an error code.
Domain error handlers are not a substitute for closing down a\nprocess when an error occurs.
\nBy the very nature of how throw works in JavaScript, there is almost\nnever any way to safely \"pick up where it left off\", without leaking\nreferences, or creating some other sort of undefined brittle state.
The safest way to respond to a thrown error is to shut down the\nprocess. Of course, in a normal web server, there may be many\nopen connections, and it is not reasonable to abruptly shut those down\nbecause an error was triggered by someone else.
\nThe better approach is to send an error response to the request that\ntriggered the error, while letting the others finish in their normal\ntime, and stop listening for new requests in that worker.
\nIn this way, domain usage goes hand-in-hand with the cluster module,\nsince the master process can fork a new worker when a worker\nencounters an error. For Node.js programs that scale to multiple\nmachines, the terminating proxy or service registry can take note of\nthe failure, and react accordingly.
For example, this is not a good idea:
\n// XXX WARNING! BAD IDEA!\n\nconst d = require('domain').create();\nd.on('error', (er) => {\n // The error won't crash the process, but what it does is worse!\n // Though we've prevented abrupt process restarting, we are leaking\n // resources like crazy if this ever happens.\n // This is no better than process.on('uncaughtException')!\n console.log(`error, but oh well ${er.message}`);\n});\nd.run(() => {\n require('http').createServer((req, res) => {\n handleRequest(req, res);\n }).listen(PORT);\n});\nBy using the context of a domain, and the resilience of separating our\nprogram into multiple worker processes, we can react more\nappropriately, and handle errors with much greater safety.
\n// Much better!\n\nconst cluster = require('cluster');\nconst PORT = +process.env.PORT || 1337;\n\nif (cluster.isMaster) {\n // A more realistic scenario would have more than 2 workers,\n // and perhaps not put the master and worker in the same file.\n //\n // It is also possible to get a bit fancier about logging, and\n // implement whatever custom logic is needed to prevent DoS\n // attacks and other bad behavior.\n //\n // See the options in the cluster documentation.\n //\n // The important thing is that the master does very little,\n // increasing our resilience to unexpected errors.\n\n cluster.fork();\n cluster.fork();\n\n cluster.on('disconnect', (worker) => {\n console.error('disconnect!');\n cluster.fork();\n });\n\n} else {\n // the worker\n //\n // This is where we put our bugs!\n\n const domain = require('domain');\n\n // See the cluster documentation for more details about using\n // worker processes to serve requests. How it works, caveats, etc.\n\n const server = require('http').createServer((req, res) => {\n const d = domain.create();\n d.on('error', (er) => {\n console.error(`error ${er.stack}`);\n\n // We're in dangerous territory!\n // By definition, something unexpected occurred,\n // which we probably didn't want.\n // Anything can happen now! Be very careful!\n\n try {\n // make sure we close down within 30 seconds\n const killtimer = setTimeout(() => {\n process.exit(1);\n }, 30000);\n // But don't keep the process open just for that!\n killtimer.unref();\n\n // stop taking new requests.\n server.close();\n\n // Let the master know we're dead. This will trigger a\n // 'disconnect' in the cluster master, and then it will fork\n // a new worker.\n cluster.worker.disconnect();\n\n // try to send an error to the request that triggered the problem\n res.statusCode = 500;\n res.setHeader('content-type', 'text/plain');\n res.end('Oops, there was a problem!\\n');\n } catch (er2) {\n // oh well, not much we can do at this point.\n console.error(`Error sending 500! ${er2.stack}`);\n }\n });\n\n // Because req and res were created before this domain existed,\n // we need to explicitly add them.\n // See the explanation of implicit vs explicit binding below.\n d.add(req);\n d.add(res);\n\n // Now run the handler function in the domain.\n d.run(() => {\n handleRequest(req, res);\n });\n });\n server.listen(PORT);\n}\n\n// This part is not important. Just an example routing thing.\n// Put fancy application logic here.\nfunction handleRequest(req, res) {\n switch (req.url) {\n case '/error':\n // We do some async stuff, and then...\n setTimeout(() => {\n // Whoops!\n flerb.bark();\n }, timeout);\n break;\n default:\n res.end('ok');\n }\n}\nAny time an Error object is routed through a domain, a few extra fields\nare added to it.
error.domain The domain that first handled the error.error.domainEmitter The event emitter that emitted an 'error' event\nwith the error object.error.domainBound The callback function which was bound to the\ndomain, and passed an error as its first argument.error.domainThrown A boolean indicating whether the error was\nthrown, emitted, or passed to a bound callback function.If domains are in use, then all new EventEmitter objects (including\nStream objects, requests, responses, etc.) will be implicitly bound to\nthe active domain at the time of their creation.
Additionally, callbacks passed to lowlevel event loop requests (such as\nto fs.open(), or other callback-taking methods) will automatically be\nbound to the active domain. If they throw, then the domain will catch\nthe error.
In order to prevent excessive memory usage, Domain objects themselves\nare not implicitly added as children of the active domain. If they\nwere, then it would be too easy to prevent request and response objects\nfrom being properly garbage collected.
To nest Domain objects as children of a parent Domain they must be\nexplicitly added.
Implicit binding routes thrown errors and 'error' events to the\nDomain's 'error' event, but does not register the EventEmitter on the\nDomain.\nImplicit binding only takes care of thrown errors and 'error' events.
Sometimes, the domain in use is not the one that ought to be used for a\nspecific event emitter. Or, the event emitter could have been created\nin the context of one domain, but ought to instead be bound to some\nother domain.
\nFor example, there could be one domain in use for an HTTP server, but\nperhaps we would like to have a separate domain to use for each request.
\nThat is possible via explicit binding.
\n// create a top-level domain for the server\nconst domain = require('domain');\nconst http = require('http');\nconst serverDomain = domain.create();\n\nserverDomain.run(() => {\n // server is created in the scope of serverDomain\n http.createServer((req, res) => {\n // req and res are also created in the scope of serverDomain\n // however, we'd prefer to have a separate domain for each request.\n // create it first thing, and add req and res to it.\n const reqd = domain.create();\n reqd.add(req);\n reqd.add(res);\n reqd.on('error', (er) => {\n console.error('Error', er, req.url);\n try {\n res.writeHead(500);\n res.end('Error occurred, sorry.');\n } catch (er2) {\n console.error('Error sending 500', er2, req.url);\n }\n });\n }).listen(1337);\n});\nThe Domain class encapsulates the functionality of routing errors and\nuncaught exceptions to the active Domain object.
Domain is a child class of EventEmitter. To handle the errors that it\ncatches, listen to its 'error' event.
An array of timers and event emitters that have been explicitly added\nto the domain.
" } ], "methods": [ { "textRaw": "domain.add(emitter)", "type": "method", "name": "add", "signatures": [ { "params": [ { "textRaw": "`emitter` {EventEmitter|Timer} emitter or timer to be added to the domain", "name": "emitter", "type": "EventEmitter|Timer", "desc": "emitter or timer to be added to the domain" } ] } ], "desc": "Explicitly adds an emitter to the domain. If any event handlers called by\nthe emitter throw an error, or if the emitter emits an 'error' event, it\nwill be routed to the domain's 'error' event, just like with implicit\nbinding.
This also works with timers that are returned from setInterval() and\nsetTimeout(). If their callback function throws, it will be caught by\nthe domain 'error' handler.
If the Timer or EventEmitter was already bound to a domain, it is removed\nfrom that one, and bound to this one instead.
The returned function will be a wrapper around the supplied callback\nfunction. When the returned function is called, any errors that are\nthrown will be routed to the domain's 'error' event.
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.bind((er, data) => {\n // if this throws, it will also be passed to the domain\n return cb(er, data ? JSON.parse(data) : null);\n }));\n}\n\nd.on('error', (er) => {\n // an error occurred somewhere.\n // if we throw it now, it will crash the program\n // with the normal line number and stack message.\n});\nThe enter() method is plumbing used by the run(), bind(), and\nintercept() methods to set the active domain. It sets domain.active and\nprocess.domain to the domain, and implicitly pushes the domain onto the domain\nstack managed by the domain module (see domain.exit() for details on the\ndomain stack). The call to enter() delimits the beginning of a chain of\nasynchronous calls and I/O operations bound to a domain.
Calling enter() changes only the active domain, and does not alter the domain\nitself. enter() and exit() can be called an arbitrary number of times on a\nsingle domain.
The exit() method exits the current domain, popping it off the domain stack.\nAny time execution is going to switch to the context of a different chain of\nasynchronous calls, it's important to ensure that the current domain is exited.\nThe call to exit() delimits either the end of or an interruption to the chain\nof asynchronous calls and I/O operations bound to a domain.
If there are multiple, nested domains bound to the current execution context,\nexit() will exit any domains nested within this domain.
Calling exit() changes only the active domain, and does not alter the domain\nitself. enter() and exit() can be called an arbitrary number of times on a\nsingle domain.
This method is almost identical to domain.bind(callback). However, in\naddition to catching thrown errors, it will also intercept Error\nobjects sent as the first argument to the function.
In this way, the common if (err) return callback(err); pattern can be replaced\nwith a single error handler in a single place.
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.intercept((data) => {\n // note, the first argument is never passed to the\n // callback since it is assumed to be the 'Error' argument\n // and thus intercepted by the domain.\n\n // if this throws, it will also be passed to the domain\n // so the error-handling logic can be moved to the 'error'\n // event on the domain instead of being repeated throughout\n // the program.\n return cb(null, JSON.parse(data));\n }));\n}\n\nd.on('error', (er) => {\n // an error occurred somewhere.\n // if we throw it now, it will crash the program\n // with the normal line number and stack message.\n});\nThe opposite of domain.add(emitter). Removes domain handling from the\nspecified emitter.
Run the supplied function in the context of the domain, implicitly\nbinding all event emitters, timers, and lowlevel requests that are\ncreated in that context. Optionally, arguments can be passed to\nthe function.
\nThis is the most basic way to use a domain.
\nconst domain = require('domain');\nconst fs = require('fs');\nconst d = domain.create();\nd.on('error', (er) => {\n console.error('Caught error!', er);\n});\nd.run(() => {\n process.nextTick(() => {\n setTimeout(() => { // simulating some various async stuff\n fs.open('non-existent file', 'r', (er, fd) => {\n if (er) throw er;\n // proceed...\n });\n }, 100);\n });\n});\nIn this example, the d.on('error') handler will be triggered, rather\nthan crashing the program.
As of Node.js 8.0.0, the handlers of Promises are run inside the domain in\nwhich the call to .then() or .catch() itself was made:
const d1 = domain.create();\nconst d2 = domain.create();\n\nlet p;\nd1.run(() => {\n p = Promise.resolve(42);\n});\n\nd2.run(() => {\n p.then((v) => {\n // running in d2\n });\n});\nA callback may be bound to a specific domain using domain.bind(callback):
const d1 = domain.create();\nconst d2 = domain.create();\n\nlet p;\nd1.run(() => {\n p = Promise.resolve(42);\n});\n\nd2.run(() => {\n p.then(p.domain.bind((v) => {\n // running in d1\n }));\n});\nNote that domains will not interfere with the error handling mechanisms for\nPromises, i.e. no 'error' event will be emitted for unhandled Promise\nrejections.
Much of the Node.js core API is built around an idiomatic asynchronous\nevent-driven architecture in which certain kinds of objects (called \"emitters\")\nemit named events that cause Function objects (\"listeners\") to be called.
For instance: a net.Server object emits an event each time a peer\nconnects to it; a fs.ReadStream emits an event when the file is opened;\na stream emits an event whenever data is available to be read.
All objects that emit events are instances of the EventEmitter class. These\nobjects expose an eventEmitter.on() function that allows one or more\nfunctions to be attached to named events emitted by the object. Typically,\nevent names are camel-cased strings but any valid JavaScript property key\ncan be used.
When the EventEmitter object emits an event, all of the functions attached\nto that specific event are called synchronously. Any values returned by the\ncalled listeners are ignored and will be discarded.
The following example shows a simple EventEmitter instance with a single\nlistener. The eventEmitter.on() method is used to register listeners, while\nthe eventEmitter.emit() method is used to trigger the event.
const EventEmitter = require('events');\n\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {\n console.log('an event occurred!');\n});\nmyEmitter.emit('event');\nThe eventEmitter.emit() method allows an arbitrary set of arguments to be\npassed to the listener functions. It is important to keep in mind that when\nan ordinary listener function is called, the standard this keyword\nis intentionally set to reference the EventEmitter instance to which the\nlistener is attached.
const myEmitter = new MyEmitter();\nmyEmitter.on('event', function(a, b) {\n console.log(a, b, this, this === myEmitter);\n // Prints:\n // a b MyEmitter {\n // domain: null,\n // _events: { event: [Function] },\n // _eventsCount: 1,\n // _maxListeners: undefined } true\n});\nmyEmitter.emit('event', 'a', 'b');\nIt is possible to use ES6 Arrow Functions as listeners, however, when doing so,\nthe this keyword will no longer reference the EventEmitter instance:
const myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n console.log(a, b, this);\n // Prints: a b {}\n});\nmyEmitter.emit('event', 'a', 'b');\nThe EventEmitter calls all listeners synchronously in the order in which\nthey were registered. This is important to ensure the proper sequencing of\nevents and to avoid race conditions or logic errors. When appropriate,\nlistener functions can switch to an asynchronous mode of operation using\nthe setImmediate() or process.nextTick() methods:
const myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n setImmediate(() => {\n console.log('this happens asynchronously');\n });\n});\nmyEmitter.emit('event', 'a', 'b');\nWhen a listener is registered using the eventEmitter.on() method, that\nlistener will be invoked every time the named event is emitted.
const myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.on('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Prints: 2\nUsing the eventEmitter.once() method, it is possible to register a listener\nthat is called at most once for a particular event. Once the event is emitted,\nthe listener is unregistered and then called.
const myEmitter = new MyEmitter();\nlet m = 0;\nmyEmitter.once('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n// Prints: 1\nmyEmitter.emit('event');\n// Ignored\nWhen an error occurs within an EventEmitter instance, the typical action is\nfor an 'error' event to be emitted. These are treated as special cases\nwithin Node.js.
If an EventEmitter does not have at least one listener registered for the\n'error' event, and an 'error' event is emitted, the error is thrown, a\nstack trace is printed, and the Node.js process exits.
const myEmitter = new MyEmitter();\nmyEmitter.emit('error', new Error('whoops!'));\n// Throws and crashes Node.js\nTo guard against crashing the Node.js process the domain module can be\nused. (Note, however, that the domain module is deprecated.)
As a best practice, listeners should always be added for the 'error' events.
const myEmitter = new MyEmitter();\nmyEmitter.on('error', (err) => {\n console.error('whoops! there was an error');\n});\nmyEmitter.emit('error', new Error('whoops!'));\n// Prints: whoops! there was an error\nThe EventEmitter class is defined and exposed by the events module:
const EventEmitter = require('events');\nAll EventEmitters emit the event 'newListener' when new listeners are\nadded and 'removeListener' when existing listeners are removed.
The EventEmitter instance will emit its own 'newListener' event before\na listener is added to its internal array of listeners.
Listeners registered for the 'newListener' event will be passed the event\nname and a reference to the listener being added.
The fact that the event is triggered before adding the listener has a subtle\nbut important side effect: any additional listeners registered to the same\nname within the 'newListener' callback will be inserted before the\nlistener that is in the process of being added.
const myEmitter = new MyEmitter();\n// Only do this once so we don't loop forever\nmyEmitter.once('newListener', (event, listener) => {\n if (event === 'event') {\n // Insert a new listener in front\n myEmitter.on('event', () => {\n console.log('B');\n });\n }\n});\nmyEmitter.on('event', () => {\n console.log('A');\n});\nmyEmitter.emit('event');\n// Prints:\n// B\n// A\nThe 'removeListener' event is emitted after the listener is removed.
A class method that returns the number of listeners for the given eventName\nregistered on the given emitter.
const myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {});\nmyEmitter.on('event', () => {});\nconsole.log(EventEmitter.listenerCount(myEmitter, 'event'));\n// Prints: 2\nAlias for emitter.on(eventName, listener).
...args <any>Synchronously calls each of the listeners registered for the event named\neventName, in the order they were registered, passing the supplied arguments\nto each.
Returns true if the event had listeners, false otherwise.
Returns an array listing the events for which the emitter has registered\nlisteners. The values in the array will be strings or Symbols.
const EventEmitter = require('events');\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => {});\nmyEE.on('bar', () => {});\n\nconst sym = Symbol('symbol');\nmyEE.on(sym, () => {});\n\nconsole.log(myEE.eventNames());\n// Prints: [ 'foo', 'bar', Symbol(symbol) ]\nReturns the current max listener value for the EventEmitter which is either\nset by emitter.setMaxListeners(n) or defaults to\nEventEmitter.defaultMaxListeners.
Returns the number of listeners listening to the event named eventName.
Returns a copy of the array of listeners for the event named eventName.
server.on('connection', (stream) => {\n console.log('someone connected!');\n});\nconsole.log(util.inspect(server.listeners('connection')));\n// Prints: [ [Function] ]\nAlias for emitter.removeListener().
Adds the listener function to the end of the listeners array for the\nevent named eventName. No checks are made to see if the listener has\nalready been added. Multiple calls passing the same combination of eventName\nand listener will result in the listener being added, and called, multiple\ntimes.
server.on('connection', (stream) => {\n console.log('someone connected!');\n});\nReturns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The\nemitter.prependListener() method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.
const myEE = new EventEmitter();\nmyEE.on('foo', () => console.log('a'));\nmyEE.prependListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\nAdds a one-time listener function for the event named eventName. The\nnext time eventName is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});\nReturns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The\nemitter.prependOnceListener() method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.
const myEE = new EventEmitter();\nmyEE.once('foo', () => console.log('a'));\nmyEE.prependOnceListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n// Prints:\n// b\n// a\nAdds the listener function to the beginning of the listeners array for the\nevent named eventName. No checks are made to see if the listener has\nalready been added. Multiple calls passing the same combination of eventName\nand listener will result in the listener being added, and called, multiple\ntimes.
server.prependListener('connection', (stream) => {\n console.log('someone connected!');\n});\nReturns a reference to the EventEmitter, so that calls can be chained.
Adds a one-time listener function for the event named eventName to the\nbeginning of the listeners array. The next time eventName is triggered, this\nlistener is removed, and then invoked.
server.prependOnceListener('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});\nReturns a reference to the EventEmitter, so that calls can be chained.
Removes all listeners, or those of the specified eventName.
Note that it is bad practice to remove listeners added elsewhere in the code,\nparticularly when the EventEmitter instance was created by some other\ncomponent or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter, so that calls can be chained.
Removes the specified listener from the listener array for the event named\neventName.
const callback = (stream) => {\n console.log('someone connected!');\n};\nserver.on('connection', callback);\n// ...\nserver.removeListener('connection', callback);\nremoveListener() will remove, at most, one instance of a listener from the\nlistener array. If any single listener has been added multiple times to the\nlistener array for the specified eventName, then removeListener() must be\ncalled multiple times to remove each instance.
Note that once an event has been emitted, all listeners attached to it at the\ntime of emitting will be called in order. This implies that any\nremoveListener() or removeAllListeners() calls after emitting and\nbefore the last listener finishes execution will not remove them from\nemit() in progress. Subsequent events will behave as expected.
const myEmitter = new MyEmitter();\n\nconst callbackA = () => {\n console.log('A');\n myEmitter.removeListener('event', callbackB);\n};\n\nconst callbackB = () => {\n console.log('B');\n};\n\nmyEmitter.on('event', callbackA);\n\nmyEmitter.on('event', callbackB);\n\n// callbackA removes listener callbackB but it will still be called.\n// Internal listener array at time of emit [callbackA, callbackB]\nmyEmitter.emit('event');\n// Prints:\n// A\n// B\n\n// callbackB is now removed.\n// Internal listener array [callbackA]\nmyEmitter.emit('event');\n// Prints:\n// A\nBecause listeners are managed using an internal array, calling this will\nchange the position indices of any listener registered after the listener\nbeing removed. This will not impact the order in which listeners are called,\nbut it means that any copies of the listener array as returned by\nthe emitter.listeners() method will need to be recreated.
When a single function has been added as a handler multiple times for a single\nevent (as in the example below), removeListener() will remove the most\nrecently added instance. In the example the once('ping')\nlistener is removed:
const ee = new EventEmitter();\n\nfunction pong() {\n console.log('pong');\n}\n\nee.on('ping', pong);\nee.once('ping', pong);\nee.removeListener('ping', pong);\n\nee.emit('ping');\nee.emit('ping');\nReturns a reference to the EventEmitter, so that calls can be chained.
By default EventEmitters will print a warning if more than 10 listeners are\nadded for a particular event. This is a useful default that helps finding\nmemory leaks. Obviously, not all events should be limited to just 10 listeners.\nThe emitter.setMaxListeners() method allows the limit to be modified for this\nspecific EventEmitter instance. The value can be set to Infinity (or 0)\nto indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
Returns a copy of the array of listeners for the event named eventName,\nincluding any wrappers (such as those created by .once()).
const emitter = new EventEmitter();\nemitter.once('log', () => console.log('log once'));\n\n// Returns a new Array with a function `onceWrapper` which has a property\n// `listener` which contains the original listener bound above\nconst listeners = emitter.rawListeners('log');\nconst logFnWrapper = listeners[0];\n\n// logs \"log once\" to the console and does not unbind the `once` event\nlogFnWrapper.listener();\n\n// logs \"log once\" to the console and removes the listener\nlogFnWrapper();\n\nemitter.on('log', () => console.log('log persistently'));\n// will return a new Array with a single function bound by `.on()` above\nconst newListeners = emitter.rawListeners('log');\n\n// logs \"log persistently\" twice\nnewListeners[0]();\nemitter.emit('log');\nBy default, a maximum of 10 listeners can be registered for any single\nevent. This limit can be changed for individual EventEmitter instances\nusing the emitter.setMaxListeners(n) method. To change the default\nfor all EventEmitter instances, the EventEmitter.defaultMaxListeners\nproperty can be used. If this value is not a positive number, a TypeError\nwill be thrown.
Take caution when setting the EventEmitter.defaultMaxListeners because the\nchange affects all EventEmitter instances, including those created before\nthe change is made. However, calling emitter.setMaxListeners(n) still has\nprecedence over EventEmitter.defaultMaxListeners.
Note that this is not a hard limit. The EventEmitter instance will allow\nmore listeners to be added but will output a trace warning to stderr indicating\nthat a \"possible EventEmitter memory leak\" has been detected. For any single\nEventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners()\nmethods can be used to temporarily avoid this warning:
emitter.setMaxListeners(emitter.getMaxListeners() + 1);\nemitter.once('event', () => {\n // do stuff\n emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));\n});\nThe --trace-warnings command line flag can be used to display the\nstack trace for such warnings.
The emitted warning can be inspected with process.on('warning') and will\nhave the additional emitter, type and count properties, referring to\nthe event emitter instance, the event’s name and the number of attached\nlisteners, respectively.\nIts name property is set to 'MaxListenersExceededWarning'.
Creates a Promise that is resolved when the EventEmitter emits the given\nevent or that is rejected when the EventEmitter emits 'error'.\nThe Promise will resolve with an array of all the arguments emitted to the\ngiven event.
const { once, EventEmitter } = require('events');\n\nasync function run() {\n const ee = new EventEmitter();\n\n process.nextTick(() => {\n ee.emit('myevent', 42);\n });\n\n const [value] = await once(ee, 'myevent');\n console.log(value);\n\n const err = new Error('kaboom');\n process.nextTick(() => {\n ee.emit('error', err);\n });\n\n try {\n await once(ee, 'myevent');\n } catch (err) {\n console.log('error happened', err);\n }\n}\n\nrun();\nThe fs module provides an API for interacting with the file system in a\nmanner closely modeled around standard POSIX functions.
To use this module:
\nconst fs = require('fs');\nAll file system operations have synchronous and asynchronous forms.
\nThe asynchronous form always takes a completion callback as its last argument.\nThe arguments passed to the completion callback depend on the method, but the\nfirst argument is always reserved for an exception. If the operation was\ncompleted successfully, then the first argument will be null or undefined.
const fs = require('fs');\n\nfs.unlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});\nExceptions that occur using synchronous operations are thrown immediately and\nmay be handled using try/catch, or may be allowed to bubble up.
const fs = require('fs');\n\ntry {\n fs.unlinkSync('/tmp/hello');\n console.log('successfully deleted /tmp/hello');\n} catch (err) {\n // handle the error\n}\nThere is no guaranteed ordering when using asynchronous methods. So the\nfollowing is prone to error because the fs.stat() operation may complete\nbefore the fs.rename() operation:
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n console.log('renamed complete');\n});\nfs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n});\nTo correctly order the operations, move the fs.stat() call into the callback\nof the fs.rename() operation:
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n fs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});\nIn busy processes, the programmer is strongly encouraged to use the\nasynchronous versions of these calls. The synchronous versions will block\nthe entire process until they complete — halting all connections.
\nWhile it is not recommended, most fs functions allow the callback argument to\nbe omitted, in which case a default callback is used that rethrows errors. To\nget a trace to the original call site, set the NODE_DEBUG environment\nvariable:
Omitting the callback function on asynchronous fs functions is deprecated and\nmay result in an error being thrown in the future.
\n$ cat script.js\nfunction bad() {\n require('fs').readFile('/');\n}\nbad();\n\n$ env NODE_DEBUG=fs node script.js\nfs.js:88\n throw backtrace;\n ^\nError: EISDIR: illegal operation on a directory, read\n <stack trace.>\nMost fs operations accept filepaths that may be specified in the form of\na string, a Buffer, or a URL object using the file: protocol.
String form paths are interpreted as UTF-8 character sequences identifying\nthe absolute or relative filename. Relative paths will be resolved relative\nto the current working directory as specified by process.cwd().
Example using an absolute path on POSIX:
\nconst fs = require('fs');\n\nfs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nExample using a relative path on POSIX (relative to process.cwd()):
fs.open('file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nPaths specified using a Buffer are useful primarily on certain POSIX\noperating systems that treat file paths as opaque byte sequences. On such\nsystems, it is possible for a single file path to contain sub-sequences that\nuse multiple character encodings. As with string paths, Buffer paths may\nbe relative or absolute:
Example using an absolute path on POSIX:
\nfs.open(Buffer.from('/open/some/file.txt'), 'r', (err, fd) => {\n if (err) throw err;\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n});\nOn Windows, Node.js follows the concept of per-drive working directory. This\nbehavior can be observed when using a drive path without a backslash. For\nexample fs.readdirSync('c:\\\\') can potentially return a different result than\nfs.readdirSync('c:'). For more information, see\nthis MSDN page.
For most fs module functions, the path or filename argument may be passed\nas a WHATWG URL object. Only URL objects using the file: protocol\nare supported.
const fs = require('fs');\nconst fileUrl = new URL('file:///tmp/hello');\n\nfs.readFileSync(fileUrl);\nfile: URLs are always absolute paths.
Using WHATWG URL objects might introduce platform-specific behaviors.
On Windows, file: URLs with a hostname convert to UNC paths, while file:\nURLs with drive letters convert to local absolute paths. file: URLs without a\nhostname nor a drive letter will result in a throw:
// On Windows :\n\n// - WHATWG file URLs with hostname convert to UNC path\n// file://hostname/p/a/t/h/file => \\\\hostname\\p\\a\\t\\h\\file\nfs.readFileSync(new URL('file://hostname/p/a/t/h/file'));\n\n// - WHATWG file URLs with drive letters convert to absolute path\n// file:///C:/tmp/hello => C:\\tmp\\hello\nfs.readFileSync(new URL('file:///C:/tmp/hello'));\n\n// - WHATWG file URLs without hostname must have a drive letters\nfs.readFileSync(new URL('file:///notdriveletter/p/a/t/h/file'));\nfs.readFileSync(new URL('file:///c/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must be absolute\nfile: URLs with drive letters must use : as a separator just after\nthe drive letter. Using another separator will result in a throw.
On all other platforms, file: URLs with a hostname are unsupported and will\nresult in a throw:
// On other platforms:\n\n// - WHATWG file URLs with hostname are unsupported\n// file://hostname/p/a/t/h/file => throw!\nfs.readFileSync(new URL('file://hostname/p/a/t/h/file'));\n// TypeError [ERR_INVALID_FILE_URL_PATH]: must be absolute\n\n// - WHATWG file URLs convert to absolute path\n// file:///tmp/hello => /tmp/hello\nfs.readFileSync(new URL('file:///tmp/hello'));\nA file: URL having encoded slash characters will result in a throw on all\nplatforms:
// On Windows\nfs.readFileSync(new URL('file:///C:/p/a/t/h/%2F'));\nfs.readFileSync(new URL('file:///C:/p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\n\n// On POSIX\nfs.readFileSync(new URL('file:///p/a/t/h/%2F'));\nfs.readFileSync(new URL('file:///p/a/t/h/%2f'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n/ characters */\nOn Windows, file: URLs having encoded backslash will result in a throw:
// On Windows\nfs.readFileSync(new URL('file:///C:/path/%5C'));\nfs.readFileSync(new URL('file:///C:/path/%5c'));\n/* TypeError [ERR_INVALID_FILE_URL_PATH]: File URL path must not include encoded\n\\ or / characters */\nOn POSIX systems, for every process, the kernel maintains a table of currently\nopen files and resources. Each open file is assigned a simple numeric\nidentifier called a file descriptor. At the system-level, all file system\noperations use these file descriptors to identify and track each specific\nfile. Windows systems use a different but conceptually similar mechanism for\ntracking resources. To simplify things for users, Node.js abstracts away the\nspecific differences between operating systems and assigns all open files a\nnumeric file descriptor.
\nThe fs.open() method is used to allocate a new file descriptor. Once\nallocated, the file descriptor may be used to read data from, write data to,\nor request information about the file.
fs.open('/open/some/file.txt', 'r', (err, fd) => {\n if (err) throw err;\n fs.fstat(fd, (err, stat) => {\n if (err) throw err;\n // use stat\n\n // always close the file descriptor!\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n });\n});\nMost operating systems limit the number of file descriptors that may be open\nat any given time so it is critical to close the descriptor when operations\nare completed. Failure to do so will result in a memory leak that will\neventually cause an application to crash.
", "type": "module", "displayName": "File Descriptors" }, { "textRaw": "Threadpool Usage", "name": "threadpool_usage", "desc": "All file system APIs except fs.FSWatcher() and those that are explicitly\nsynchronous use libuv's threadpool, which can have surprising and negative\nperformance implications for some applications. See the\nUV_THREADPOOL_SIZE documentation for more information.
The fs.promises API provides an alternative set of asynchronous file system\nmethods that return Promise objects rather than using callbacks. The\nAPI is accessible via require('fs').promises.
A FileHandle object is a wrapper for a numeric file descriptor.\nInstances of FileHandle are distinct from numeric file descriptors\nin that, if the FileHandle is not explicitly closed using the\nfilehandle.close() method, they will automatically close the file descriptor\nand will emit a process warning, thereby helping to prevent memory leaks.
Instances of the FileHandle object are created internally by the\nfsPromises.open() method.
Unlike the callback-based API (fs.fstat(), fs.fchown(), fs.fchmod(), and\nso on), a numeric file descriptor is not used by the promise-based API. Instead,\nthe promise-based API uses the FileHandle class in order to help avoid\naccidental leaking of unclosed file descriptors after a Promise is resolved or\nrejected.
Asynchronously append data to this file, creating the file if it does not yet\nexist. data can be a string or a Buffer. The Promise will be\nresolved with no arguments upon success.
If options is a string, then it specifies the encoding.
The FileHandle must have been opened for appending.
Modifies the permissions on the file. The Promise is resolved with no\narguments upon success.
Changes the ownership of the file then resolves the Promise with no arguments\nupon success.
Closes the file descriptor.
\nconst fsPromises = require('fs').promises;\nasync function openAndClose() {\n let filehandle;\n try {\n filehandle = await fsPromises.open('thefile.txt', 'r');\n } finally {\n if (filehandle !== undefined)\n await filehandle.close();\n }\n}\nAsynchronous fdatasync(2). The Promise is resolved with no arguments upon\nsuccess.
Read data from the file.
\nbuffer is the buffer that the data will be written to.
offset is the offset in the buffer to start writing at.
length is an integer specifying the number of bytes to read.
position is an argument specifying where to begin reading from in the file.\nIf position is null, data will be read from the current file position,\nand the file position will be updated.\nIf position is an integer, the file position will remain unchanged.
Following successful read, the Promise is resolved with an object with a\nbytesRead property specifying the number of bytes read, and a buffer\nproperty that is a reference to the passed in buffer argument.
Asynchronously reads the entire contents of a file.
\nThe Promise is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding), the data is returned as a Buffer\nobject. Otherwise, the data will be a string.
If options is a string, then it specifies the encoding.
When the path is a directory, the behavior of fsPromises.readFile() is\nplatform-specific. On macOS, Linux, and Windows, the promise will be rejected\nwith an error. On FreeBSD, a representation of the directory's contents will be\nreturned.
The FileHandle has to support reading.
If one or more filehandle.read() calls are made on a file handle and then a\nfilehandle.readFile() call is made, the data will be read from the current\nposition till the end of the file. It doesn't always read from the beginning\nof the file.
Retrieves the fs.Stats for the file.
Asynchronous fsync(2). The Promise is resolved with no arguments upon\nsuccess.
Truncates the file then resolves the Promise with no arguments upon success.
If the file was larger than len bytes, only the first len bytes will be\nretained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nconst fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(4);\n } finally {\n if (filehandle) {\n // close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints: Node\n}\n\ndoTruncate().catch(console.error);\nIf the file previously was shorter than len bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'):
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\nasync function doTruncate() {\n let filehandle = null;\n try {\n filehandle = await fsPromises.open('temp.txt', 'r+');\n await filehandle.truncate(10);\n } finally {\n if (filehandle) {\n // close the file if it is opened.\n await filehandle.close();\n }\n }\n console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints Node.js\\0\\0\\0\n}\n\ndoTruncate().catch(console.error);\nThe last three bytes are null bytes ('\\0'), to compensate the over-truncation.
Change the file system timestamps of the object referenced by the FileHandle\nthen resolves the Promise with no arguments upon success.
This function does not work on AIX versions before 7.1, it will resolve the\nPromise with an error using code UV_ENOSYS.
Write buffer to the file.
The Promise is resolved with an object containing a bytesWritten property\nidentifying the number of bytes written, and a buffer property containing\na reference to the buffer written.
offset determines the part of the buffer to be written, and length is\nan integer specifying the number of bytes to write.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position. See pwrite(2).
It is unsafe to use filehandle.write() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected). For this\nscenario, fs.createWriteStream() is strongly recommended.
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "filehandle.write(string[, position[, encoding]])", "type": "method", "name": "write", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer", "optional": true }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`", "optional": true } ] } ], "desc": "Write string to the file. If string is not a string, then\nthe value will be coerced to one.
The Promise is resolved with an object containing a bytesWritten property\nidentifying the number of bytes written, and a buffer property containing\na reference to the string written.
position refers to the offset from the beginning of the file where this data\nshould be written. If the type of position is not a number the data\nwill be written at the current position. See pwrite(2).
encoding is the expected string encoding.
It is unsafe to use filehandle.write() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected). For this\nscenario, fs.createWriteStream() is strongly recommended.
On Linux, positional writes do not work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "filehandle.writeFile(data, options)", "type": "method", "name": "writeFile", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`data` {string|Buffer|Uint8Array}", "name": "data", "type": "string|Buffer|Uint8Array" }, { "textRaw": "`options` {Object|string}", "name": "options", "type": "Object|string", "options": [ { "textRaw": "`encoding` {string|null} **Default:** `'utf8'`", "name": "encoding", "type": "string|null", "default": "`'utf8'`" }, { "textRaw": "`mode` {integer} **Default:** `0o666`", "name": "mode", "type": "integer", "default": "`0o666`" }, { "textRaw": "`flag` {string} See [support of file system `flags`][]. **Default:** `'w'`.", "name": "flag", "type": "string", "default": "`'w'`", "desc": "See [support of file system `flags`][]." } ] } ] } ], "desc": "Asynchronously writes data to a file, replacing the file if it already exists.\ndata can be a string or a buffer. The Promise will be resolved with no\narguments upon success.
The encoding option is ignored if data is a buffer.
If options is a string, then it specifies the encoding.
The FileHandle has to support writing.
It is unsafe to use filehandle.writeFile() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected).
If one or more filehandle.write() calls are made on a file handle and then a\nfilehandle.writeFile() call is made, the data will be written from the\ncurrent position till the end of the file. It doesn't always write from the\nbeginning of the file.
Tests a user's permissions for the file or directory specified by path.\nThe mode argument is an optional integer that specifies the accessibility\nchecks to be performed. Check File Access Constants for possible values\nof mode. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK).
If the accessibility check is successful, the Promise is resolved with no\nvalue. If any of the accessibility checks fail, the Promise is rejected\nwith an Error object. The following example checks if the file\n/etc/passwd can be read and written by the current process.
const fs = require('fs');\nconst fsPromises = fs.promises;\n\nfsPromises.access('/etc/passwd', fs.constants.R_OK | fs.constants.W_OK)\n .then(() => console.log('can access'))\n .catch(() => console.error('cannot access'));\nUsing fsPromises.access() to check for the accessibility of a file before\ncalling fsPromises.open() is not recommended. Doing so introduces a race\ncondition, since other processes may change the file's state between the two\ncalls. Instead, user code should open/read/write the file directly and handle\nthe error raised if the file is not accessible.
Asynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer. The Promise will be\nresolved with no arguments upon success.
If options is a string, then it specifies the encoding.
The path may be specified as a FileHandle that has been opened\nfor appending (using fsPromises.open()).
Changes the permissions of a file then resolves the Promise with no\narguments upon succces.
Changes the ownership of a file then resolves the Promise with no arguments\nupon success.
Asynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. The Promise will be resolved with no arguments upon success.
Node.js makes no guarantees about the atomicity of the copy operation. If an\nerror occurs after the destination file has been opened for writing, Node.js\nwill attempt to remove the destination.
\nflags is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL - The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE - The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE - The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const fsPromises = require('fs').promises;\n\n// destination.txt will be created or overwritten by default.\nfsPromises.copyFile('source.txt', 'destination.txt')\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\nIf the third argument is a number, then it specifies flags:
const fs = require('fs');\nconst fsPromises = fs.promises;\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfsPromises.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL)\n .then(() => console.log('source.txt was copied to destination.txt'))\n .catch(() => console.log('The file could not be copied'));\nChanges the permissions on a symbolic link then resolves the Promise with\nno arguments upon success. This method is only implemented on macOS.
Changes the ownership on a symbolic link then resolves the Promise with\nno arguments upon success.
Asynchronous link(2). The Promise is resolved with no arguments upon success.
Asynchronous lstat(2). The Promise is resolved with the fs.Stats object\nfor the given symbolic link path.
Asynchronously creates a directory then resolves the Promise with no\narguments upon success.
The optional options argument can be an integer specifying mode (permission\nand sticky bits), or an object with a mode property and a recursive\nproperty indicating whether parent folders should be created.
Creates a unique temporary directory and resolves the Promise with the created\nfolder path. A unique directory name is generated by appending six random\ncharacters to the end of the provided prefix.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
fsPromises.mkdtemp(path.join(os.tmpdir(), 'foo-'))\n .catch(console.error);\nThe fsPromises.mkdtemp() method will append the six randomly selected\ncharacters directly to the prefix string. For instance, given a directory\n/tmp, if the intention is to create a temporary directory within /tmp, the\nprefix must end with a trailing platform-specific path separator\n(require('path').sep).
Asynchronous file open that returns a Promise that, when resolved, yields a\nFileHandle object. See open(2).
mode sets the file mode (permission and sticky bits), but only if the file was\ncreated.
Some characters (< > : \" / \\ | ? *) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Reads the contents of a directory then resolves the Promise with an array\nof the names of the files in the directory excluding '.' and '..'.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames. If the encoding is set to 'buffer', the filenames returned\nwill be passed as Buffer objects.
If options.withFileTypes is set to true, the resolved array will contain\nfs.Dirent objects.
Asynchronously reads the entire contents of a file.
\nThe Promise is resolved with the contents of the file. If no encoding is\nspecified (using options.encoding), the data is returned as a Buffer\nobject. Otherwise, the data will be a string.
If options is a string, then it specifies the encoding.
When the path is a directory, the behavior of fsPromises.readFile() is\nplatform-specific. On macOS, Linux, and Windows, the promise will be rejected\nwith an error. On FreeBSD, a representation of the directory's contents will be\nreturned.
Any specified FileHandle has to support reading.
Asynchronous readlink(2). The Promise is resolved with the linkString upon\nsuccess.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path returned. If the encoding is set to 'buffer', the link path\nreturned will be passed as a Buffer object.
Determines the actual location of path using the same semantics as the\nfs.realpath.native() function then resolves the Promise with the resolved\npath.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path. If the encoding is set to 'buffer', the path returned will be\npassed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Renames oldPath to newPath and resolves the Promise with no arguments\nupon success.
Removes the directory identified by path then resolves the Promise with\nno arguments upon success.
Using fsPromises.rmdir() on a file (not a directory) results in the\nPromise being rejected with an ENOENT error on Windows and an ENOTDIR\nerror on POSIX.
The Promise is resolved with the fs.Stats object for the given path.
Creates a symbolic link then resolves the Promise with no arguments upon\nsuccess.
The type argument is only used on Windows platforms and can be one of 'dir',\n'file', or 'junction'. Windows junction points require the destination path\nto be absolute. When using 'junction', the target argument will\nautomatically be normalized to absolute path.
Truncates the path then resolves the Promise with no arguments upon\nsuccess. The path must be a string or Buffer.
Asynchronous unlink(2). The Promise is resolved with no arguments upon\nsuccess.
Change the file system timestamps of the object referenced by path then\nresolves the Promise with no arguments upon success.
The atime and mtime arguments follow these rules:
Dates, or a\nnumeric string like '123456789.0'.NaN, Infinity or\n-Infinity, an Error will be thrown.Asynchronously writes data to a file, replacing the file if it already exists.\ndata can be a string or a buffer. The Promise will be resolved with no\narguments upon success.
The encoding option is ignored if data is a buffer.
If options is a string, then it specifies the encoding.
Any specified FileHandle has to support writing.
It is unsafe to use fsPromises.writeFile() multiple times on the same file\nwithout waiting for the Promise to be resolved (or rejected).
The following constants are exported by fs.constants.
Not every constant will be available on every operating system.
", "modules": [ { "textRaw": "File Access Constants", "name": "file_access_constants", "desc": "The following constants are meant for use with fs.access().
| Constant | \nDescription | \n
|---|---|
F_OK | \n Flag indicating that the file is visible to the calling process.\n This is useful for determining if a file exists, but says nothing\n about rwx permissions. Default if no mode is specified. | \n
R_OK | \n Flag indicating that the file can be read by the calling process. | \n
W_OK | \n Flag indicating that the file can be written by the calling\n process. | \n
X_OK | \n Flag indicating that the file can be executed by the calling\n process. This has no effect on Windows\n (will behave like fs.constants.F_OK). | \n
The following constants are meant for use with fs.copyFile().
| Constant | \nDescription | \n
|---|---|
COPYFILE_EXCL | \n If present, the copy operation will fail with an error if the\n destination path already exists. | \n
COPYFILE_FICLONE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then a fallback copy mechanism is used. | \n
COPYFILE_FICLONE_FORCE | \n If present, the copy operation will attempt to create a\n copy-on-write reflink. If the underlying platform does not support\n copy-on-write, then the operation will fail with an error. | \n
The following constants are meant for use with fs.open().
| Constant | \nDescription | \n
|---|---|
O_RDONLY | \n Flag indicating to open a file for read-only access. | \n
O_WRONLY | \n Flag indicating to open a file for write-only access. | \n
O_RDWR | \n Flag indicating to open a file for read-write access. | \n
O_CREAT | \n Flag indicating to create the file if it does not already exist. | \n
O_EXCL | \n Flag indicating that opening a file should fail if the\n O_CREAT flag is set and the file already exists. | \n
O_NOCTTY | \n Flag indicating that if path identifies a terminal device, opening the\n path shall not cause that terminal to become the controlling terminal for\n the process (if the process does not already have one). | \n
O_TRUNC | \n Flag indicating that if the file exists and is a regular file, and the\n file is opened successfully for write access, its length shall be truncated\n to zero. | \n
O_APPEND | \n Flag indicating that data will be appended to the end of the file. | \n
O_DIRECTORY | \n Flag indicating that the open should fail if the path is not a\n directory. | \n
O_NOATIME | \n Flag indicating reading accesses to the file system will no longer\n result in an update to the atime information associated with\n the file. This flag is available on Linux operating systems only. | \n
O_NOFOLLOW | \n Flag indicating that the open should fail if the path is a symbolic\n link. | \n
O_SYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for file integrity. | \n
O_DSYNC | \n Flag indicating that the file is opened for synchronized I/O with write\n operations waiting for data integrity. | \n
O_SYMLINK | \n Flag indicating to open the symbolic link itself rather than the\n resource it is pointing to. | \n
O_DIRECT | \n When set, an attempt will be made to minimize caching effects of file\n I/O. | \n
O_NONBLOCK | \n Flag indicating to open the file in nonblocking mode when possible. | \n
The following constants are meant for use with the fs.Stats object's\nmode property for determining a file's type.
| Constant | \nDescription | \n
|---|---|
S_IFMT | \n Bit mask used to extract the file type code. | \n
S_IFREG | \n File type constant for a regular file. | \n
S_IFDIR | \n File type constant for a directory. | \n
S_IFCHR | \n File type constant for a character-oriented device file. | \n
S_IFBLK | \n File type constant for a block-oriented device file. | \n
S_IFIFO | \n File type constant for a FIFO/pipe. | \n
S_IFLNK | \n File type constant for a symbolic link. | \n
S_IFSOCK | \n File type constant for a socket. | \n
The following constants are meant for use with the fs.Stats object's\nmode property for determining the access permissions for a file.
| Constant | \nDescription | \n
|---|---|
S_IRWXU | \n File mode indicating readable, writable, and executable by owner. | \n
S_IRUSR | \n File mode indicating readable by owner. | \n
S_IWUSR | \n File mode indicating writable by owner. | \n
S_IXUSR | \n File mode indicating executable by owner. | \n
S_IRWXG | \n File mode indicating readable, writable, and executable by group. | \n
S_IRGRP | \n File mode indicating readable by group. | \n
S_IWGRP | \n File mode indicating writable by group. | \n
S_IXGRP | \n File mode indicating executable by group. | \n
S_IRWXO | \n File mode indicating readable, writable, and executable by others. | \n
S_IROTH | \n File mode indicating readable by others. | \n
S_IWOTH | \n File mode indicating writable by others. | \n
S_IXOTH | \n File mode indicating executable by others. | \n
The following flags are available wherever the flag option takes a\nstring:
'a' - Open file for appending.\nThe file is created if it does not exist.
'ax' - Like 'a' but fails if the path exists.
'a+' - Open file for reading and appending.\nThe file is created if it does not exist.
'ax+' - Like 'a+' but fails if the path exists.
'as' - Open file for appending in synchronous mode.\nThe file is created if it does not exist.
'as+' - Open file for reading and appending in synchronous mode.\nThe file is created if it does not exist.
'r' - Open file for reading.\nAn exception occurs if the file does not exist.
'r+' - Open file for reading and writing.\nAn exception occurs if the file does not exist.
'rs+' - Open file for reading and writing in synchronous mode. Instructs\nthe operating system to bypass the local file system cache.
This is primarily useful for opening files on NFS mounts as it allows\nskipping the potentially stale local cache. It has a very real impact on\nI/O performance so using this flag is not recommended unless it is needed.
\nThis doesn't turn fs.open() or fsPromises.open() into a synchronous\nblocking call. If synchronous operation is desired, something like\nfs.openSync() should be used.
'w' - Open file for writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx' - Like 'w' but fails if the path exists.
'w+' - Open file for reading and writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx+' - Like 'w+' but fails if the path exists.
flag can also be a number as documented by open(2); commonly used constants\nare available from fs.constants. On Windows, flags are translated to\ntheir equivalent ones where applicable, e.g. O_WRONLY to FILE_GENERIC_WRITE,\nor O_EXCL|O_CREAT to CREATE_NEW, as accepted by CreateFileW.
The exclusive flag 'x' (O_EXCL flag in open(2)) ensures that path is newly\ncreated. On POSIX systems, path is considered to exist even if it is a symlink\nto a non-existent file. The exclusive flag may or may not work with network\nfile systems.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nModifying a file rather than replacing it may require a flags mode of 'r+'\nrather than the default mode 'w'.
The behavior of some flags are platform-specific. As such, opening a directory\non macOS and Linux with the 'a+' flag - see example below - will return an\nerror. In contrast, on Windows and FreeBSD, a file descriptor or a FileHandle\nwill be returned.
// macOS and Linux\nfs.open('<directory>', 'a+', (err, fd) => {\n // => [Error: EISDIR: illegal operation on a directory, open <directory>]\n});\n\n// Windows and FreeBSD\nfs.open('<directory>', 'a+', (err, fd) => {\n // => null, <fd>\n});\nOn Windows, opening an existing hidden file using the 'w' flag (either\nthrough fs.open() or fs.writeFile() or fsPromises.open()) will fail with\nEPERM. Existing hidden files can be opened for writing with the 'r+' flag.
A call to fs.ftruncate() or filehandle.truncate() can be used to reset\nthe file contents.
When fs.readdir() or fs.readdirSync() is called with the\nwithFileTypes option set to true, the resulting array is filled with\nfs.Dirent objects, rather than strings or Buffers.
Returns true if the fs.Dirent object describes a block device.
Returns true if the fs.Dirent object describes a character device.
Returns true if the fs.Dirent object describes a file system\ndirectory.
Returns true if the fs.Dirent object describes a first-in-first-out\n(FIFO) pipe.
Returns true if the fs.Dirent object describes a regular file.
Returns true if the fs.Dirent object describes a socket.
Returns true if the fs.Dirent object describes a symbolic link.
The file name that this fs.Dirent object refers to. The type of this\nvalue is determined by the options.encoding passed to fs.readdir() or\nfs.readdirSync().
A successful call to fs.watch() method will return a new fs.FSWatcher\nobject.
All fs.FSWatcher objects are EventEmitter's that will emit a 'change'\nevent whenever a specific watched file is modified.
Emitted when something changes in a watched directory or file.\nSee more details in fs.watch().
The filename argument may not be provided depending on operating system\nsupport. If filename is provided, it will be provided as a Buffer if\nfs.watch() is called with its encoding option set to 'buffer', otherwise\nfilename will be a UTF-8 string.
// Example when handled through fs.watch() listener\nfs.watch('./tmp', { encoding: 'buffer' }, (eventType, filename) => {\n if (filename) {\n console.log(filename);\n // Prints: <Buffer ...>\n }\n});\nEmitted when the watcher stops watching for changes. The closed\nfs.FSWatcher object is no longer usable in the event handler.
Emitted when an error occurs while watching the file. The errored\nfs.FSWatcher object is no longer usable in the event handler.
Stop watching for changes on the given fs.FSWatcher. Once stopped, the\nfs.FSWatcher object is no longer usable.
A successful call to fs.createReadStream() will return a new fs.ReadStream\nobject.
All fs.ReadStream objects are Readable Streams.
Emitted when the fs.ReadStream's underlying file descriptor has been closed.
Emitted when the fs.ReadStream's file descriptor has been opened.
Emitted when the fs.ReadStream is ready to be used.
Fires immediately after 'open'.
The number of bytes that have been read so far.
" }, { "textRaw": "`path` {string|Buffer}", "type": "string|Buffer", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is reading from as specified in the first\nargument to fs.createReadStream(). If path is passed as a string, then\nreadStream.path will be a string. If path is passed as a Buffer, then\nreadStream.path will be a Buffer.
This property is true if the underlying file has not been opened yet,\ni.e. before the 'ready' event is emitted.
A fs.Stats object provides information about a file.
Objects returned from fs.stat(), fs.lstat() and fs.fstat() and\ntheir synchronous counterparts are of this type.\nIf bigint in the options passed to those methods is true, the numeric values\nwill be bigint instead of number.
Stats {\n dev: 2114,\n ino: 48064969,\n mode: 33188,\n nlink: 1,\n uid: 85,\n gid: 100,\n rdev: 0,\n size: 527,\n blksize: 4096,\n blocks: 8,\n atimeMs: 1318289051000.1,\n mtimeMs: 1318289051000.1,\n ctimeMs: 1318289051000.1,\n birthtimeMs: 1318289051000.1,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\nbigint version:
Stats {\n dev: 2114n,\n ino: 48064969n,\n mode: 33188n,\n nlink: 1n,\n uid: 85n,\n gid: 100n,\n rdev: 0n,\n size: 527n,\n blksize: 4096n,\n blocks: 8n,\n atimeMs: 1318289051000n,\n mtimeMs: 1318289051000n,\n ctimeMs: 1318289051000n,\n birthtimeMs: 1318289051000n,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT }\nReturns true if the fs.Stats object describes a block device.
Returns true if the fs.Stats object describes a character device.
Returns true if the fs.Stats object describes a file system directory.
Returns true if the fs.Stats object describes a first-in-first-out (FIFO)\npipe.
Returns true if the fs.Stats object describes a regular file.
Returns true if the fs.Stats object describes a socket.
Returns true if the fs.Stats object describes a symbolic link.
This method is only valid when using fs.lstat().
The numeric identifier of the device containing the file.
" }, { "textRaw": "`ino` {number|bigint}", "type": "number|bigint", "name": "ino", "desc": "The file system specific \"Inode\" number for the file.
" }, { "textRaw": "`mode` {number|bigint}", "type": "number|bigint", "name": "mode", "desc": "A bit-field describing the file type and mode.
" }, { "textRaw": "`nlink` {number|bigint}", "type": "number|bigint", "name": "nlink", "desc": "The number of hard-links that exist for the file.
" }, { "textRaw": "`uid` {number|bigint}", "type": "number|bigint", "name": "uid", "desc": "The numeric user identifier of the user that owns the file (POSIX).
" }, { "textRaw": "`gid` {number|bigint}", "type": "number|bigint", "name": "gid", "desc": "The numeric group identifier of the group that owns the file (POSIX).
" }, { "textRaw": "`rdev` {number|bigint}", "type": "number|bigint", "name": "rdev", "desc": "A numeric device identifier if the file is considered \"special\".
" }, { "textRaw": "`size` {number|bigint}", "type": "number|bigint", "name": "size", "desc": "The size of the file in bytes.
" }, { "textRaw": "`blksize` {number|bigint}", "type": "number|bigint", "name": "blksize", "desc": "The file system block size for i/o operations.
" }, { "textRaw": "`blocks` {number|bigint}", "type": "number|bigint", "name": "blocks", "desc": "The number of blocks allocated for this file.
" }, { "textRaw": "`atimeMs` {number|bigint}", "type": "number|bigint", "name": "atimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was accessed expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`mtimeMs` {number|bigint}", "type": "number|bigint", "name": "mtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`ctimeMs` {number|bigint}", "type": "number|bigint", "name": "ctimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed expressed\nin milliseconds since the POSIX Epoch.
" }, { "textRaw": "`birthtimeMs` {number|bigint}", "type": "number|bigint", "name": "birthtimeMs", "meta": { "added": [ "v8.1.0" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file expressed in\nmilliseconds since the POSIX Epoch.
" }, { "textRaw": "`atime` {Date}", "type": "Date", "name": "atime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was accessed.
" }, { "textRaw": "`mtime` {Date}", "type": "Date", "name": "mtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time this file was modified.
" }, { "textRaw": "`ctime` {Date}", "type": "Date", "name": "ctime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the last time the file status was changed.
" }, { "textRaw": "`birthtime` {Date}", "type": "Date", "name": "birthtime", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "desc": "The timestamp indicating the creation time of this file.
" } ], "modules": [ { "textRaw": "Stat Time Values", "name": "stat_time_values", "desc": "The atimeMs, mtimeMs, ctimeMs, birthtimeMs properties are\nnumbers that hold the corresponding times in milliseconds. Their\nprecision is platform specific. atime, mtime, ctime, and birthtime are\nDate object alternate representations of the various times. The\nDate and number values are not connected. Assigning a new number value, or\nmutating the Date value, will not be reflected in the corresponding alternate\nrepresentation.
The times in the stat object have the following semantics:
\natime \"Access Time\" - Time when file data last accessed. Changed\nby the mknod(2), utimes(2), and read(2) system calls.mtime \"Modified Time\" - Time when file data last modified.\nChanged by the mknod(2), utimes(2), and write(2) system calls.ctime \"Change Time\" - Time when file status was last changed\n(inode data modification). Changed by the chmod(2), chown(2),\nlink(2), mknod(2), rename(2), unlink(2), utimes(2),\nread(2), and write(2) system calls.birthtime \"Birth Time\" - Time of file creation. Set once when the\nfile is created. On filesystems where birthtime is not available,\nthis field may instead hold either the ctime or\n1970-01-01T00:00Z (ie, unix epoch timestamp 0). This value may be greater\nthan atime or mtime in this case. On Darwin and other FreeBSD variants,\nalso set if the atime is explicitly set to an earlier value than the current\nbirthtime using the utimes(2) system call.Prior to Node.js 0.12, the ctime held the birthtime on Windows systems. As\nof 0.12, ctime is not \"creation time\", and on Unix systems, it never was.
WriteStream is a Writable Stream.
Emitted when the WriteStream's underlying file descriptor has been closed.
Emitted when the WriteStream's file is opened.
Emitted when the fs.WriteStream is ready to be used.
Fires immediately after 'open'.
The number of bytes written so far. Does not include data that is still queued\nfor writing.
" }, { "textRaw": "writeStream.path", "name": "path", "meta": { "added": [ "v0.1.93" ], "changes": [] }, "desc": "The path to the file the stream is writing to as specified in the first\nargument to fs.createWriteStream(). If path is passed as a string, then\nwriteStream.path will be a string. If path is passed as a Buffer, then\nwriteStream.path will be a Buffer.
This property is true if the underlying file has not been opened yet,\ni.e. before the 'ready' event is emitted.
Tests a user's permissions for the file or directory specified by path.\nThe mode argument is an optional integer that specifies the accessibility\nchecks to be performed. Check File Access Constants for possible values\nof mode. It is possible to create a mask consisting of the bitwise OR of\ntwo or more values (e.g. fs.constants.W_OK | fs.constants.R_OK).
The final argument, callback, is a callback function that is invoked with\na possible error argument. If any of the accessibility checks fail, the error\nargument will be an Error object. The following examples check if\npackage.json exists, and if it is readable or writable.
const file = 'package.json';\n\n// Check if the file exists in the current directory.\nfs.access(file, fs.constants.F_OK, (err) => {\n console.log(`${file} ${err ? 'does not exist' : 'exists'}`);\n});\n\n// Check if the file is readable.\nfs.access(file, fs.constants.R_OK, (err) => {\n console.log(`${file} ${err ? 'is not readable' : 'is readable'}`);\n});\n\n// Check if the file is writable.\nfs.access(file, fs.constants.W_OK, (err) => {\n console.log(`${file} ${err ? 'is not writable' : 'is writable'}`);\n});\n\n// Check if the file exists in the current directory, and if it is writable.\nfs.access(file, fs.constants.F_OK | fs.constants.W_OK, (err) => {\n if (err) {\n console.error(\n `${file} ${err.code === 'ENOENT' ? 'does not exist' : 'is read-only'}`);\n } else {\n console.log(`${file} exists, and it is writable`);\n }\n});\nUsing fs.access() to check for the accessibility of a file before calling\nfs.open(), fs.readFile() or fs.writeFile() is not recommended. Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file is not accessible.
write (NOT RECOMMENDED)
\nfs.access('myfile', (err) => {\n if (!err) {\n console.error('myfile already exists');\n return;\n }\n\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n});\nwrite (RECOMMENDED)
\nfs.open('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n writeMyData(fd);\n});\nread (NOT RECOMMENDED)
\nfs.access('myfile', (err) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n});\nread (RECOMMENDED)
\nfs.open('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n readMyData(fd);\n});\nThe \"not recommended\" examples above check for accessibility and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the accessibility of a file only if the file will not be\nused directly, for example when its accessibility is a signal from another\nprocess.
\nOn Windows, access-control policies (ACLs) on a directory may limit access to\na file or directory. The fs.access() function, however, does not check the\nACL and therefore may report that a path is accessible even if the ACL restricts\nthe user from reading or writing to it.
Synchronously tests a user's permissions for the file or directory specified\nby path. The mode argument is an optional integer that specifies the\naccessibility checks to be performed. Check File Access Constants for\npossible values of mode. It is possible to create a mask consisting of\nthe bitwise OR of two or more values\n(e.g. fs.constants.W_OK | fs.constants.R_OK).
If any of the accessibility checks fail, an Error will be thrown. Otherwise,\nthe method will return undefined.
try {\n fs.accessSync('etc/passwd', fs.constants.R_OK | fs.constants.W_OK);\n console.log('can read/write');\n} catch (err) {\n console.error('no access!');\n}\nAsynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer.
fs.appendFile('message.txt', 'data to append', (err) => {\n if (err) throw err;\n console.log('The \"data to append\" was appended to file!');\n});\nIf options is a string, then it specifies the encoding:
fs.appendFile('message.txt', 'data to append', 'utf8', callback);\nThe path may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open() or fs.openSync()). The file descriptor will\nnot be closed automatically.
fs.open('message.txt', 'a', (err, fd) => {\n if (err) throw err;\n fs.appendFile(fd, 'data to append', 'utf8', (err) => {\n fs.close(fd, (err) => {\n if (err) throw err;\n });\n if (err) throw err;\n });\n});\nSynchronously append data to a file, creating the file if it does not yet\nexist. data can be a string or a Buffer.
try {\n fs.appendFileSync('message.txt', 'data to append');\n console.log('The \"data to append\" was appended to file!');\n} catch (err) {\n /* Handle the error */\n}\nIf options is a string, then it specifies the encoding:
fs.appendFileSync('message.txt', 'data to append', 'utf8');\nThe path may be specified as a numeric file descriptor that has been opened\nfor appending (using fs.open() or fs.openSync()). The file descriptor will\nnot be closed automatically.
let fd;\n\ntry {\n fd = fs.openSync('message.txt', 'a');\n fs.appendFileSync(fd, 'data to append', 'utf8');\n} catch (err) {\n /* Handle the error */\n} finally {\n if (fd !== undefined)\n fs.closeSync(fd);\n}\nAsynchronously changes the permissions of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee also: chmod(2).
The mode argument used in both the fs.chmod() and fs.chmodSync()\nmethods is a numeric bitmask created using a logical OR of the following\nconstants:
| Constant | \nOctal | \nDescription | \n
|---|---|---|
fs.constants.S_IRUSR | \n0o400 | \nread by owner | \n
fs.constants.S_IWUSR | \n0o200 | \nwrite by owner | \n
fs.constants.S_IXUSR | \n0o100 | \nexecute/search by owner | \n
fs.constants.S_IRGRP | \n0o40 | \nread by group | \n
fs.constants.S_IWGRP | \n0o20 | \nwrite by group | \n
fs.constants.S_IXGRP | \n0o10 | \nexecute/search by group | \n
fs.constants.S_IROTH | \n0o4 | \nread by others | \n
fs.constants.S_IWOTH | \n0o2 | \nwrite by others | \n
fs.constants.S_IXOTH | \n0o1 | \nexecute/search by others | \n
An easier method of constructing the mode is to use a sequence of three\noctal digits (e.g. 765). The left-most digit (7 in the example), specifies\nthe permissions for the file owner. The middle digit (6 in the example),\nspecifies permissions for the group. The right-most digit (5 in the example),\nspecifies the permissions for others.
| Number | \nDescription | \n
|---|---|
7 | \nread, write, and execute | \n
6 | \nread and write | \n
5 | \nread and execute | \n
4 | \nread only | \n
3 | \nwrite and execute | \n
2 | \nwrite only | \n
1 | \nexecute only | \n
0 | \nno permission | \n
For example, the octal value 0o765 means:
When using raw numbers where file modes are expected, any value larger than\n0o777 may result in platform-specific behaviors that are not supported to work\nconsistently. Therefore constants like S_ISVTX, S_ISGID or S_ISUID are not\nexposed in fs.constants.
Caveats: on Windows only the write permission can be changed, and the\ndistinction among the permissions of group, owner or others is not\nimplemented.
", "type": "module", "displayName": "File modes" } ] }, { "textRaw": "fs.chmodSync(path, mode)", "type": "method", "name": "chmodSync", "meta": { "added": [ "v0.6.7" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer}", "name": "mode", "type": "integer" } ] } ], "desc": "For detailed information, see the documentation of the asynchronous version of\nthis API: fs.chmod().
See also: chmod(2).
Asynchronously changes owner and group of a file. No arguments other than a\npossible exception are given to the completion callback.
\nSee also: chown(2).
Synchronously changes owner and group of a file. Returns undefined.\nThis is the synchronous version of fs.chown().
See also: chown(2).
Asynchronous close(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous close(2). Returns undefined.
Asynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. No arguments other than a possible exception are given to the\ncallback function. Node.js makes no guarantees about the atomicity of the copy\noperation. If an error occurs after the destination file has been opened for\nwriting, Node.js will attempt to remove the destination.
flags is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL - The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE - The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE - The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const fs = require('fs');\n\n// destination.txt will be created or overwritten by default.\nfs.copyFile('source.txt', 'destination.txt', (err) => {\n if (err) throw err;\n console.log('source.txt was copied to destination.txt');\n});\nIf the third argument is a number, then it specifies flags:
const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFile('source.txt', 'destination.txt', COPYFILE_EXCL, callback);\nSynchronously copies src to dest. By default, dest is overwritten if it\nalready exists. Returns undefined. Node.js makes no guarantees about the\natomicity of the copy operation. If an error occurs after the destination file\nhas been opened for writing, Node.js will attempt to remove the destination.
flags is an optional integer that specifies the behavior\nof the copy operation. It is possible to create a mask consisting of the bitwise\nOR of two or more values (e.g.\nfs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE).
fs.constants.COPYFILE_EXCL - The copy operation will fail if dest already\nexists.fs.constants.COPYFILE_FICLONE - The copy operation will attempt to create a\ncopy-on-write reflink. If the platform does not support copy-on-write, then a\nfallback copy mechanism is used.fs.constants.COPYFILE_FICLONE_FORCE - The copy operation will attempt to\ncreate a copy-on-write reflink. If the platform does not support copy-on-write,\nthen the operation will fail.const fs = require('fs');\n\n// destination.txt will be created or overwritten by default.\nfs.copyFileSync('source.txt', 'destination.txt');\nconsole.log('source.txt was copied to destination.txt');\nIf the third argument is a number, then it specifies flags:
const fs = require('fs');\nconst { COPYFILE_EXCL } = fs.constants;\n\n// By using COPYFILE_EXCL, the operation will fail if destination.txt exists.\nfs.copyFileSync('source.txt', 'destination.txt', COPYFILE_EXCL);\nUnlike the 16 kb default highWaterMark for a readable stream, the stream\nreturned by this method has a default highWaterMark of 64 kb.
options can include start and end values to read a range of bytes from\nthe file instead of the entire file. Both start and end are inclusive and\nstart counting at 0. If fd is specified and start is omitted or undefined,\nfs.createReadStream() reads sequentially from the current file position.\nThe encoding can be any one of those accepted by Buffer.
If fd is specified, ReadStream will ignore the path argument and will use\nthe specified file descriptor. This means that no 'open' event will be\nemitted. fd should be blocking; non-blocking fds should be passed to\nnet.Socket.
If fd points to a character device that only supports blocking reads\n(such as keyboard or sound card), read operations do not finish until data is\navailable. This can prevent the process from exiting and the stream from\nclosing naturally.
const fs = require('fs');\n// Create a stream from some character device.\nconst stream = fs.createReadStream('/dev/input/event0');\nsetTimeout(() => {\n stream.close(); // This may not close the stream.\n // Artificially marking end-of-stream, as if the underlying resource had\n // indicated end-of-file by itself, allows the stream to close.\n // This does not cancel pending read operations, and if there is such an\n // operation, the process may still not be able to exit successfully\n // until it finishes.\n stream.push(null);\n stream.read(0);\n}, 100);\nIf autoClose is false, then the file descriptor won't be closed, even if\nthere's an error. It is the application's responsibility to close it and make\nsure there's no file descriptor leak. If autoClose is set to true (default\nbehavior), on 'error' or 'end' the file descriptor will be closed\nautomatically.
mode sets the file mode (permission and sticky bits), but only if the\nfile was created.
An example to read the last 10 bytes of a file which is 100 bytes long:
\nfs.createReadStream('sample.txt', { start: 90, end: 99 });\nIf options is a string, then it specifies the encoding.
options may also include a start option to allow writing data at\nsome position past the beginning of the file. Modifying a file rather\nthan replacing it may require a flags mode of r+ rather than the\ndefault mode w. The encoding can be any one of those accepted by\nBuffer.
If autoClose is set to true (default behavior) on 'error' or 'finish'\nthe file descriptor will be closed automatically. If autoClose is false,\nthen the file descriptor won't be closed, even if there's an error.\nIt is the application's responsibility to close it and make sure there's no\nfile descriptor leak.
Like ReadStream, if fd is specified, WriteStream will ignore the\npath argument and will use the specified file descriptor. This means that no\n'open' event will be emitted. fd should be blocking; non-blocking fds\nshould be passed to net.Socket.
If options is a string, then it specifies the encoding.
Test whether or not the given path exists by checking with the file system.\nThen call the callback argument with either true or false:
fs.exists('/etc/passwd', (exists) => {\n console.log(exists ? 'it\\'s there' : 'no passwd!');\n});\nThe parameters for this callback are not consistent with other Node.js\ncallbacks. Normally, the first parameter to a Node.js callback is an err\nparameter, optionally followed by other parameters. The fs.exists() callback\nhas only one boolean parameter. This is one reason fs.access() is recommended\ninstead of fs.exists().
Using fs.exists() to check for the existence of a file before calling\nfs.open(), fs.readFile() or fs.writeFile() is not recommended. Doing\nso introduces a race condition, since other processes may change the file's\nstate between the two calls. Instead, user code should open/read/write the\nfile directly and handle the error raised if the file does not exist.
write (NOT RECOMMENDED)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n console.error('myfile already exists');\n } else {\n fs.open('myfile', 'wx', (err, fd) => {\n if (err) throw err;\n writeMyData(fd);\n });\n }\n});\nwrite (RECOMMENDED)
\nfs.open('myfile', 'wx', (err, fd) => {\n if (err) {\n if (err.code === 'EEXIST') {\n console.error('myfile already exists');\n return;\n }\n\n throw err;\n }\n\n writeMyData(fd);\n});\nread (NOT RECOMMENDED)
\nfs.exists('myfile', (exists) => {\n if (exists) {\n fs.open('myfile', 'r', (err, fd) => {\n if (err) throw err;\n readMyData(fd);\n });\n } else {\n console.error('myfile does not exist');\n }\n});\nread (RECOMMENDED)
\nfs.open('myfile', 'r', (err, fd) => {\n if (err) {\n if (err.code === 'ENOENT') {\n console.error('myfile does not exist');\n return;\n }\n\n throw err;\n }\n\n readMyData(fd);\n});\nThe \"not recommended\" examples above check for existence and then use the\nfile; the \"recommended\" examples are better because they use the file directly\nand handle the error, if any.
\nIn general, check for the existence of a file only if the file won’t be\nused directly, for example when its existence is a signal from another\nprocess.
" }, { "textRaw": "fs.existsSync(path)", "type": "method", "name": "existsSync", "meta": { "added": [ "v0.1.21" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" } ] } ], "desc": "Returns true if the path exists, false otherwise.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.exists().
fs.exists() is deprecated, but fs.existsSync() is not. The callback\nparameter to fs.exists() accepts parameters that are inconsistent with other\nNode.js callbacks. fs.existsSync() does not use a callback.
Asynchronous fchmod(2). No arguments other than a possible exception\nare given to the completion callback.
Synchronous fchmod(2). Returns undefined.
Asynchronous fchown(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous fchown(2). Returns undefined.
Asynchronous fdatasync(2). No arguments other than a possible exception are\ngiven to the completion callback.
Synchronous fdatasync(2). Returns undefined.
Asynchronous fstat(2). The callback gets two arguments (err, stats) where\nstats is an fs.Stats object. fstat() is identical to stat(),\nexcept that the file to be stat-ed is specified by the file descriptor fd.
Synchronous fstat(2).
Asynchronous fsync(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous fsync(2). Returns undefined.
Asynchronous ftruncate(2). No arguments other than a possible exception are\ngiven to the completion callback.
If the file referred to by the file descriptor was larger than len bytes, only\nthe first len bytes will be retained in the file.
For example, the following program retains only the first four bytes of the\nfile:
\nconsole.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// truncate the file to first four bytes\nfs.ftruncate(fd, 4, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt', 'utf8'));\n});\n// Prints: Node\nIf the file previously was shorter than len bytes, it is extended, and the\nextended part is filled with null bytes ('\\0'):
console.log(fs.readFileSync('temp.txt', 'utf8'));\n// Prints: Node.js\n\n// get the file descriptor of the file to be truncated\nconst fd = fs.openSync('temp.txt', 'r+');\n\n// truncate the file to 10 bytes, whereas the actual size is 7 bytes\nfs.ftruncate(fd, 10, (err) => {\n assert.ifError(err);\n console.log(fs.readFileSync('temp.txt'));\n});\n// Prints: <Buffer 4e 6f 64 65 2e 6a 73 00 00 00>\n// ('Node.js\\0\\0\\0' in UTF8)\nThe last three bytes are null bytes ('\\0'), to compensate the over-truncation.
Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.ftruncate().
Change the file system timestamps of the object referenced by the supplied file\ndescriptor. See fs.utimes().
This function does not work on AIX versions before 7.1, it will return the\nerror UV_ENOSYS.
Synchronous version of fs.futimes(). Returns undefined.
Asynchronous lchmod(2). No arguments other than a possible exception\nare given to the completion callback.
Only available on macOS.
" }, { "textRaw": "fs.lchmodSync(path, mode)", "type": "method", "name": "lchmodSync", "meta": { "deprecated": [ "v0.4.7" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`mode` {integer}", "name": "mode", "type": "integer" } ] } ], "desc": "Synchronous lchmod(2). Returns undefined.
Asynchronous lchown(2). No arguments other than a possible exception are given\nto the completion callback.
Synchronous lchown(2). Returns undefined.
Asynchronous link(2). No arguments other than a possible exception are given to\nthe completion callback.
Synchronous link(2). Returns undefined.
Asynchronous lstat(2). The callback gets two arguments (err, stats) where\nstats is a fs.Stats object. lstat() is identical to stat(),\nexcept that if path is a symbolic link, then the link itself is stat-ed,\nnot the file that it refers to.
Synchronous lstat(2).
Asynchronously creates a directory. No arguments other than a possible exception\nare given to the completion callback.
\nThe optional options argument can be an integer specifying mode (permission\nand sticky bits), or an object with a mode property and a recursive\nproperty indicating whether parent folders should be created.
// Creates /tmp/a/apple, regardless of whether `/tmp` and /tmp/a exist.\nfs.mkdir('/tmp/a/apple', { recursive: true }, (err) => {\n if (err) throw err;\n});\nOn Windows, using fs.mkdir() on the root directory even with recursion will\nresult in an error:
fs.mkdir('/', { recursive: true }, (err) => {\n // => [Error: EPERM: operation not permitted, mkdir 'C:\\']\n});\nSee also: mkdir(2).
Synchronously creates a directory. Returns undefined.\nThis is the synchronous version of fs.mkdir().
See also: mkdir(2).
Creates a unique temporary directory.
\nGenerates six random characters to be appended behind a required\nprefix to create a unique temporary directory.
The created folder path is passed as a string to the callback's second\nparameter.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
fs.mkdtemp(path.join(os.tmpdir(), 'foo-'), (err, folder) => {\n if (err) throw err;\n console.log(folder);\n // Prints: /tmp/foo-itXde2 or C:\\Users\\...\\AppData\\Local\\Temp\\foo-itXde2\n});\nThe fs.mkdtemp() method will append the six randomly selected characters\ndirectly to the prefix string. For instance, given a directory /tmp, if the\nintention is to create a temporary directory within /tmp, the prefix\nmust end with a trailing platform-specific path separator\n(require('path').sep).
// The parent directory for the new temporary directory\nconst tmpDir = os.tmpdir();\n\n// This method is *INCORRECT*:\nfs.mkdtemp(tmpDir, (err, folder) => {\n if (err) throw err;\n console.log(folder);\n // Will print something similar to `/tmpabc123`.\n // A new temporary directory is created at the file system root\n // rather than *within* the /tmp directory.\n});\n\n// This method is *CORRECT*:\nconst { sep } = require('path');\nfs.mkdtemp(`${tmpDir}${sep}`, (err, folder) => {\n if (err) throw err;\n console.log(folder);\n // Will print something similar to `/tmp/abc123`.\n // A new temporary directory is created within\n // the /tmp directory.\n});\nReturns the created folder path.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.mkdtemp().
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use.
Asynchronous file open. See open(2).
mode sets the file mode (permission and sticky bits), but only if the file was\ncreated. On Windows, only the write permission can be manipulated; see\nfs.chmod().
The callback gets two arguments (err, fd).
Some characters (< > : \" / \\ | ? *) are reserved under Windows as documented\nby Naming Files, Paths, and Namespaces. Under NTFS, if the filename contains\na colon, Node.js will open a file system stream, as described by\nthis MSDN page.
Functions based on fs.open() exhibit this behavior as well:\nfs.writeFile(), fs.readFile(), etc.
Returns an integer representing the file descriptor.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.open().
Read data from the file specified by fd.
buffer is the buffer that the data will be written to.
offset is the offset in the buffer to start writing at.
length is an integer specifying the number of bytes to read.
position is an argument specifying where to begin reading from in the file.\nIf position is null, data will be read from the current file position,\nand the file position will be updated.\nIf position is an integer, the file position will remain unchanged.
The callback is given the three arguments, (err, bytesRead, buffer).
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with bytesRead and buffer properties.
Asynchronous readdir(3). Reads the contents of a directory.\nThe callback gets two arguments (err, files) where files is an array of\nthe names of the files in the directory excluding '.' and '..'.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames passed to the callback. If the encoding is set to 'buffer',\nthe filenames returned will be passed as Buffer objects.
If options.withFileTypes is set to true, the files array will contain\nfs.Dirent objects.
Synchronous readdir(3).
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe filenames returned. If the encoding is set to 'buffer',\nthe filenames returned will be passed as Buffer objects.
If options.withFileTypes is set to true, the result will contain\nfs.Dirent objects.
Asynchronously reads the entire contents of a file.
\nfs.readFile('/etc/passwd', (err, data) => {\n if (err) throw err;\n console.log(data);\n});\nThe callback is passed two arguments (err, data), where data is the\ncontents of the file.
If no encoding is specified, then the raw buffer is returned.
\nIf options is a string, then it specifies the encoding:
fs.readFile('/etc/passwd', 'utf8', callback);\nWhen the path is a directory, the behavior of fs.readFile() and\nfs.readFileSync() is platform-specific. On macOS, Linux, and Windows, an\nerror will be returned. On FreeBSD, a representation of the directory's contents\nwill be returned.
// macOS, Linux, and Windows\nfs.readFile('<directory>', (err, data) => {\n // => [Error: EISDIR: illegal operation on a directory, read <directory>]\n});\n\n// FreeBSD\nfs.readFile('<directory>', (err, data) => {\n // => null, <data>\n});\nThe fs.readFile() function buffers the entire file. To minimize memory costs,\nwhen possible prefer streaming via fs.createReadStream().
path, it will not be closed\nautomatically.'Hello World' and six bytes are read with the file descriptor,\nthe call to fs.readFile() with the same file descriptor, would give\n'World', rather than 'Hello World'.Returns the contents of the path.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.readFile().
If the encoding option is specified then this function returns a\nstring. Otherwise it returns a buffer.
Similar to fs.readFile(), when the path is a directory, the behavior of\nfs.readFileSync() is platform-specific.
// macOS, Linux, and Windows\nfs.readFileSync('<directory>');\n// => [Error: EISDIR: illegal operation on a directory, read <directory>]\n\n// FreeBSD\nfs.readFileSync('<directory>'); // => <data>\nAsynchronous readlink(2). The callback gets two arguments (err, linkString).
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path passed to the callback. If the encoding is set to 'buffer',\nthe link path returned will be passed as a Buffer object.
Synchronous readlink(2). Returns the symbolic link's string value.
The optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe link path returned. If the encoding is set to 'buffer',\nthe link path returned will be passed as a Buffer object.
Returns the number of bytesRead.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.read().
Asynchronously computes the canonical pathname by resolving ., .. and\nsymbolic links.
A canonical pathname is not necessarily unique. Hard links and bind mounts can\nexpose a file system entity through many pathnames.
\nThis function behaves like realpath(3), with some exceptions:
No case conversion is performed on case-insensitive file systems.
\nThe maximum number of symbolic links is platform-independent and generally\n(much) higher than what the native realpath(3) implementation supports.
The callback gets two arguments (err, resolvedPath). May use process.cwd\nto resolve relative paths.
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path passed to the callback. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
If path resolves to a socket or a pipe, the function will return a system\ndependent name for that object.
Asynchronous realpath(3).
The callback gets two arguments (err, resolvedPath).
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path passed to the callback. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Returns the resolved pathname.
\nFor detailed information, see the documentation of the asynchronous version of\nthis API: fs.realpath().
Synchronous realpath(3).
Only paths that can be converted to UTF8 strings are supported.
\nThe optional options argument can be a string specifying an encoding, or an\nobject with an encoding property specifying the character encoding to use for\nthe path returned. If the encoding is set to 'buffer',\nthe path returned will be passed as a Buffer object.
On Linux, when Node.js is linked against musl libc, the procfs file system must\nbe mounted on /proc in order for this function to work. Glibc does not have\nthis restriction.
Asynchronously rename file at oldPath to the pathname provided\nas newPath. In the case that newPath already exists, it will\nbe overwritten. No arguments other than a possible exception are\ngiven to the completion callback.
See also: rename(2).
fs.rename('oldFile.txt', 'newFile.txt', (err) => {\n if (err) throw err;\n console.log('Rename complete!');\n});\nSynchronous rename(2). Returns undefined.
Asynchronous rmdir(2). No arguments other than a possible exception are given\nto the completion callback.
Using fs.rmdir() on a file (not a directory) results in an ENOENT error on\nWindows and an ENOTDIR error on POSIX.
Synchronous rmdir(2). Returns undefined.
Using fs.rmdirSync() on a file (not a directory) results in an ENOENT error\non Windows and an ENOTDIR error on POSIX.
Asynchronous stat(2). The callback gets two arguments (err, stats) where\nstats is an fs.Stats object.
In case of an error, the err.code will be one of Common System Errors.
Using fs.stat() to check for the existence of a file before calling\nfs.open(), fs.readFile() or fs.writeFile() is not recommended.\nInstead, user code should open/read/write the file directly and handle the\nerror raised if the file is not available.
To check if a file exists without manipulating it afterwards, fs.access()\nis recommended.
Synchronous stat(2).
Asynchronous symlink(2). No arguments other than a possible exception are given\nto the completion callback. The type argument can be set to 'dir',\n'file', or 'junction' and is only available on\nWindows (ignored on other platforms). Windows junction points require the\ndestination path to be absolute. When using 'junction', the target argument\nwill automatically be normalized to absolute path.
Here is an example below:
\nfs.symlink('./foo', './new-port', callback);\nIt creates a symbolic link named \"new-port\" that points to \"foo\".
" }, { "textRaw": "fs.symlinkSync(target, path[, type])", "type": "method", "name": "symlinkSync", "meta": { "added": [ "v0.1.31" ], "changes": [ { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `target` and `path` parameters can be WHATWG `URL` objects using `file:` protocol. Support is currently still *experimental*." } ] }, "signatures": [ { "params": [ { "textRaw": "`target` {string|Buffer|URL}", "name": "target", "type": "string|Buffer|URL" }, { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`type` {string} **Default:** `'file'`", "name": "type", "type": "string", "default": "`'file'`", "optional": true } ] } ], "desc": "Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.symlink().
Asynchronous truncate(2). No arguments other than a possible exception are\ngiven to the completion callback. A file descriptor can also be passed as the\nfirst argument. In this case, fs.ftruncate() is called.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "fs.truncateSync(path[, len])", "type": "method", "name": "truncateSync", "meta": { "added": [ "v0.8.6" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`len` {integer} **Default:** `0`", "name": "len", "type": "integer", "default": "`0`", "optional": true } ] } ], "desc": "Synchronous truncate(2). Returns undefined. A file descriptor can also be\npassed as the first argument. In this case, fs.ftruncateSync() is called.
Passing a file descriptor is deprecated and may result in an error being thrown\nin the future.
" }, { "textRaw": "fs.unlink(path, callback)", "type": "method", "name": "unlink", "meta": { "added": [ "v0.0.2" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.6.0", "pr-url": "https://github.com/nodejs/node/pull/10739", "description": "The `path` parameter can be a WHATWG `URL` object using `file:` protocol. Support is currently still *experimental*." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`path` {string|Buffer|URL}", "name": "path", "type": "string|Buffer|URL" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" } ] } ] } ], "desc": "Asynchronously removes a file or symbolic link. No arguments other than a\npossible exception are given to the completion callback.
\n// Assuming that 'path/file.txt' is a regular file.\nfs.unlink('path/file.txt', (err) => {\n if (err) throw err;\n console.log('path/file.txt was deleted');\n});\nfs.unlink() will not work on a directory, empty or otherwise. To remove a\ndirectory, use fs.rmdir().
See also: unlink(2).
Synchronous unlink(2). Returns undefined.
Stop watching for changes on filename. If listener is specified, only that\nparticular listener is removed. Otherwise, all listeners are removed,\neffectively stopping watching of filename.
Calling fs.unwatchFile() with a filename that is not being watched is a\nno-op, not an error.
Using fs.watch() is more efficient than fs.watchFile() and\nfs.unwatchFile(). fs.watch() should be used instead of fs.watchFile()\nand fs.unwatchFile() when possible.
Change the file system timestamps of the object referenced by path.
The atime and mtime arguments follow these rules:
Dates, or a\nnumeric string like '123456789.0'.NaN, Infinity or\n-Infinity, an Error will be thrown.Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.utimes().
Watch for changes on filename, where filename is either a file or a\ndirectory.
The second argument is optional. If options is provided as a string, it\nspecifies the encoding. Otherwise options should be passed as an object.
The listener callback gets two arguments (eventType, filename). eventType\nis either 'rename' or 'change', and filename is the name of the file\nwhich triggered the event.
On most platforms, 'rename' is emitted whenever a filename appears or\ndisappears in the directory.
The listener callback is attached to the 'change' event fired by\nfs.FSWatcher, but it is not the same thing as the 'change' value of\neventType.
The fs.watch API is not 100% consistent across platforms, and is\nunavailable in some situations.
The recursive option is only supported on macOS and Windows.
", "miscs": [ { "textRaw": "Availability", "name": "Availability", "type": "misc", "desc": "This feature depends on the underlying operating system providing a way\nto be notified of filesystem changes.
\ninotify(7).kqueue(2).kqueue(2) for files and FSEvents for directories.event ports.ReadDirectoryChangesW.AHAFS, which must be enabled.If the underlying functionality is not available for some reason, then\nfs.watch will not be able to function. For example, watching files or\ndirectories can be unreliable, and in some cases impossible, on network file\nsystems (NFS, SMB, etc), or host file systems when using virtualization software\nsuch as Vagrant, Docker, etc.
It is still possible to use fs.watchFile(), which uses stat polling, but\nthis method is slower and less reliable.
On Linux and macOS systems, fs.watch() resolves the path to an inode and\nwatches the inode. If the watched path is deleted and recreated, it is assigned\na new inode. The watch will emit an event for the delete but will continue\nwatching the original inode. Events for the new inode will not be emitted.\nThis is expected behavior.
AIX files retain the same inode for the lifetime of a file. Saving and closing a\nwatched file on AIX will result in two notifications (one for adding new\ncontent, and one for truncation).
" }, { "textRaw": "Filename Argument", "name": "Filename Argument", "type": "misc", "desc": "Providing filename argument in the callback is only supported on Linux,\nmacOS, Windows, and AIX. Even on supported platforms, filename is not always\nguaranteed to be provided. Therefore, don't assume that filename argument is\nalways provided in the callback, and have some fallback logic if it is null.
fs.watch('somedir', (eventType, filename) => {\n console.log(`event type is: ${eventType}`);\n if (filename) {\n console.log(`filename provided: ${filename}`);\n } else {\n console.log('filename not provided');\n }\n});\nWatch for changes on filename. The callback listener will be called each\ntime the file is accessed.
The options argument may be omitted. If provided, it should be an object. The\noptions object may contain a boolean named persistent that indicates\nwhether the process should continue to run as long as files are being watched.\nThe options object may specify an interval property indicating how often the\ntarget should be polled in milliseconds.
The listener gets two arguments the current stat object and the previous\nstat object:
fs.watchFile('message.text', (curr, prev) => {\n console.log(`the current mtime is: ${curr.mtime}`);\n console.log(`the previous mtime was: ${prev.mtime}`);\n});\nThese stat objects are instances of fs.Stat.
To be notified when the file was modified, not just accessed, it is necessary\nto compare curr.mtime and prev.mtime.
When an fs.watchFile operation results in an ENOENT error, it\nwill invoke the listener once, with all the fields zeroed (or, for dates, the\nUnix Epoch). In Windows, blksize and blocks fields will be undefined,\ninstead of zero. If the file is created later on, the listener will be called\nagain, with the latest stat objects. This is a change in functionality since\nv0.10.
Using fs.watch() is more efficient than fs.watchFile and\nfs.unwatchFile. fs.watch should be used instead of fs.watchFile and\nfs.unwatchFile when possible.
When a file being watched by fs.watchFile() disappears and reappears,\nthen the previousStat reported in the second callback event (the file's\nreappearance) will be the same as the previousStat of the first callback\nevent (its disappearance).
This happens when:
\nWrite buffer to the file specified by fd.
offset determines the part of the buffer to be written, and length is\nan integer specifying the number of bytes to write.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number', the data will be written\nat the current position. See pwrite(2).
The callback will be given three arguments (err, bytesWritten, buffer) where\nbytesWritten specifies how many bytes were written from buffer.
If this method is invoked as its util.promisify()ed version, it returns\na Promise for an Object with bytesWritten and buffer properties.
It is unsafe to use fs.write() multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream() is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
" }, { "textRaw": "fs.write(fd, string[, position[, encoding]], callback)", "type": "method", "name": "write", "meta": { "added": [ "v0.11.5" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/12562", "description": "The `callback` parameter is no longer optional. Not passing it will throw a `TypeError` at runtime." }, { "version": "v7.2.0", "pr-url": "https://github.com/nodejs/node/pull/7856", "description": "The `position` parameter is optional now." }, { "version": "v7.0.0", "pr-url": "https://github.com/nodejs/node/pull/7897", "description": "The `callback` parameter is no longer optional. Not passing it will emit a deprecation warning with id DEP0013." } ] }, "signatures": [ { "params": [ { "textRaw": "`fd` {integer}", "name": "fd", "type": "integer" }, { "textRaw": "`string` {string}", "name": "string", "type": "string" }, { "textRaw": "`position` {integer}", "name": "position", "type": "integer", "optional": true }, { "textRaw": "`encoding` {string} **Default:** `'utf8'`", "name": "encoding", "type": "string", "default": "`'utf8'`", "optional": true }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "options": [ { "textRaw": "`err` {Error}", "name": "err", "type": "Error" }, { "textRaw": "`written` {integer}", "name": "written", "type": "integer" }, { "textRaw": "`string` {string}", "name": "string", "type": "string" } ] } ] } ], "desc": "Write string to the file specified by fd. If string is not a string, then\nthe value will be coerced to one.
position refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number' the data will be written at\nthe current position. See pwrite(2).
encoding is the expected string encoding.
The callback will receive the arguments (err, written, string) where written\nspecifies how many bytes the passed string required to be written. Bytes\nwritten is not necessarily the same as string characters written. See\nBuffer.byteLength.
It is unsafe to use fs.write() multiple times on the same file without waiting\nfor the callback. For this scenario, fs.createWriteStream() is\nrecommended.
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.
\nOn Windows, if the file descriptor is connected to the console (e.g. fd == 1\nor stdout) a string containing non-ASCII characters will not be rendered\nproperly by default, regardless of the encoding used.\nIt is possible to configure the console to render UTF-8 properly by changing the\nactive codepage with the chcp 65001 command. See the chcp docs for more\ndetails.
Asynchronously writes data to a file, replacing the file if it already exists.\ndata can be a string or a buffer.
The encoding option is ignored if data is a buffer.
const data = new Uint8Array(Buffer.from('Hello Node.js'));\nfs.writeFile('message.txt', data, (err) => {\n if (err) throw err;\n console.log('The file has been saved!');\n});\nIf options is a string, then it specifies the encoding:
fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);\nIt is unsafe to use fs.writeFile() multiple times on the same file without\nwaiting for the callback. For this scenario, fs.createWriteStream() is\nrecommended.
file, it will not be closed\nautomatically.'Hello World' and the newly written content is 'Aloha',\nthen the contents of the file would be 'Aloha World', rather than just\n'Aloha'.Returns undefined.
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.writeFile().
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, buffer...).
For detailed information, see the documentation of the asynchronous version of\nthis API: fs.write(fd, string...).
Returns an object containing commonly used constants for file system\noperations. The specific constants currently defined are described in\nFS Constants.
" } ], "type": "module", "displayName": "fs" }, { "textRaw": "HTTP", "name": "http", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "To use the HTTP server and client one must require('http').
The HTTP interfaces in Node.js are designed to support many features\nof the protocol which have been traditionally difficult to use.\nIn particular, large, possibly chunk-encoded, messages. The interface is\ncareful to never buffer entire requests or responses — the\nuser is able to stream data.
\nHTTP message headers are represented by an object like this:
\n\n{ 'content-length': '123',\n 'content-type': 'text/plain',\n 'connection': 'keep-alive',\n 'host': 'mysite.com',\n 'accept': '*/*' }\nKeys are lowercased. Values are not modified.
\nIn order to support the full spectrum of possible HTTP applications, Node.js's\nHTTP API is very low-level. It deals with stream handling and message\nparsing only. It parses a message into headers and body but it does not\nparse the actual headers or the body.
\nSee message.headers for details on how duplicate headers are handled.
The raw headers as they were received are retained in the rawHeaders\nproperty, which is an array of [key, value, key2, value2, ...]. For\nexample, the previous message header object might have a rawHeaders\nlist like the following:
[ 'ConTent-Length', '123456',\n 'content-LENGTH', '123',\n 'content-type', 'text/plain',\n 'CONNECTION', 'keep-alive',\n 'Host', 'mysite.com',\n 'accepT', '*/*' ]\nAn Agent is responsible for managing connection persistence\nand reuse for HTTP clients. It maintains a queue of pending requests\nfor a given host and port, reusing a single socket connection for each\nuntil the queue is empty, at which time the socket is either destroyed\nor put into a pool where it is kept to be used again for requests to the\nsame host and port. Whether it is destroyed or pooled depends on the\nkeepAlive option.
Pooled connections have TCP Keep-Alive enabled for them, but servers may\nstill close idle connections, in which case they will be removed from the\npool and a new connection will be made when a new HTTP request is made for\nthat host and port. Servers may also refuse to allow multiple requests\nover the same connection, in which case the connection will have to be\nremade for every request and cannot be pooled. The Agent will still make\nthe requests to that server, but each one will occur over a new connection.
When a connection is closed by the client or the server, it is removed\nfrom the pool. Any unused sockets in the pool will be unrefed so as not\nto keep the Node.js process running when there are no outstanding requests.\n(see socket.unref()).
It is good practice, to destroy() an Agent instance when it is no\nlonger in use, because unused sockets consume OS resources.
Sockets are removed from an agent when the socket emits either\na 'close' event or an 'agentRemove' event. When intending to keep one\nHTTP request open for a long time without keeping it in the agent, something\nlike the following may be done:
http.get(options, (res) => {\n // Do stuff\n}).on('socket', (socket) => {\n socket.emit('agentRemove');\n});\nAn agent may also be used for an individual request. By providing\n{agent: false} as an option to the http.get() or http.request()\nfunctions, a one-time use Agent with default options will be used\nfor the client connection.
agent:false:
http.get({\n hostname: 'localhost',\n port: 80,\n path: '/',\n agent: false // create a new agent just for this one request\n}, (res) => {\n // Do stuff with response\n});\nProduces a socket/stream to be used for HTTP requests.
\nBy default, this function is the same as net.createConnection(). However,\ncustom agents may override this method in case greater flexibility is desired.
A socket/stream can be supplied in one of two ways: by returning the\nsocket/stream from this function, or by passing the socket/stream to callback.
callback has a signature of (err, stream).
Called when socket is detached from a request and could be persisted by the\nAgent. Default behavior is to:
socket.setKeepAlive(true, this.keepAliveMsecs);\nsocket.unref();\nreturn true;\nThis method can be overridden by a particular Agent subclass. If this\nmethod returns a falsy value, the socket will be destroyed instead of persisting\nit for use with the next request.
Called when socket is attached to request after being persisted because of\nthe keep-alive options. Default behavior is to:
socket.ref();\nThis method can be overridden by a particular Agent subclass.
Destroy any sockets that are currently in use by the agent.
\nIt is usually not necessary to do this. However, if using an\nagent with keepAlive enabled, then it is best to explicitly shut down\nthe agent when it will no longer be used. Otherwise,\nsockets may hang open for quite a long time before the server\nterminates them.
Get a unique name for a set of request options, to determine whether a\nconnection can be reused. For an HTTP agent, this returns\nhost:port:localAddress or host:port:localAddress:family. For an HTTPS agent,\nthe name includes the CA, cert, ciphers, and other HTTPS/TLS-specific options\nthat determine socket reusability.
An object which contains arrays of sockets currently awaiting use by\nthe agent when keepAlive is enabled. Do not modify.
By default set to 256. For agents with keepAlive enabled, this\nsets the maximum number of sockets that will be left open in the free\nstate.
By default set to Infinity. Determines how many concurrent sockets the agent\ncan have open per origin. Origin is the returned value of agent.getName().
An object which contains queues of requests that have not yet been assigned to\nsockets. Do not modify.
" }, { "textRaw": "`sockets` {Object}", "type": "Object", "name": "sockets", "meta": { "added": [ "v0.3.6" ], "changes": [] }, "desc": "An object which contains arrays of sockets currently in use by the\nagent. Do not modify.
" } ], "signatures": [ { "params": [ { "textRaw": "`options` {Object} Set of configurable options to set on the agent. Can have the following fields:", "name": "options", "type": "Object", "desc": "Set of configurable options to set on the agent. Can have the following fields:", "options": [ { "textRaw": "`keepAlive` {boolean} Keep sockets around even when there are no outstanding requests, so they can be used for future requests without having to reestablish a TCP connection. Not to be confused with the `keep-alive` value of the `Connection` header. The `Connection: keep-alive` header is always sent when using an agent except when the `Connection` header is explicitly specified or when the `keepAlive` and `maxSockets` options are respectively set to `false` and `Infinity`, in which case `Connection: close` will be used. **Default:** `false`.", "name": "keepAlive", "type": "boolean", "default": "`false`", "desc": "Keep sockets around even when there are no outstanding requests, so they can be used for future requests without having to reestablish a TCP connection. Not to be confused with the `keep-alive` value of the `Connection` header. The `Connection: keep-alive` header is always sent when using an agent except when the `Connection` header is explicitly specified or when the `keepAlive` and `maxSockets` options are respectively set to `false` and `Infinity`, in which case `Connection: close` will be used." }, { "textRaw": "`keepAliveMsecs` {number} When using the `keepAlive` option, specifies the [initial delay](net.html#net_socket_setkeepalive_enable_initialdelay) for TCP Keep-Alive packets. Ignored when the `keepAlive` option is `false` or `undefined`. **Default:** `1000`.", "name": "keepAliveMsecs", "type": "number", "default": "`1000`", "desc": "When using the `keepAlive` option, specifies the [initial delay](net.html#net_socket_setkeepalive_enable_initialdelay) for TCP Keep-Alive packets. Ignored when the `keepAlive` option is `false` or `undefined`." }, { "textRaw": "`maxSockets` {number} Maximum number of sockets to allow per host. Each request will use a new socket until the maximum is reached. **Default:** `Infinity`.", "name": "maxSockets", "type": "number", "default": "`Infinity`", "desc": "Maximum number of sockets to allow per host. Each request will use a new socket until the maximum is reached." }, { "textRaw": "`maxFreeSockets` {number} Maximum number of sockets to leave open in a free state. Only relevant if `keepAlive` is set to `true`. **Default:** `256`.", "name": "maxFreeSockets", "type": "number", "default": "`256`", "desc": "Maximum number of sockets to leave open in a free state. Only relevant if `keepAlive` is set to `true`." }, { "textRaw": "`timeout` {number} Socket timeout in milliseconds. This will set the timeout when the socket is created.", "name": "timeout", "type": "number", "desc": "Socket timeout in milliseconds. This will set the timeout when the socket is created." } ], "optional": true } ], "desc": "options in socket.connect() are also supported.
The default http.globalAgent that is used by http.request() has all\nof these values set to their respective defaults.
To configure any of them, a custom http.Agent instance must be created.
const http = require('http');\nconst keepAliveAgent = new http.Agent({ keepAlive: true });\noptions.agent = keepAliveAgent;\nhttp.request(options, onResponseCallback);\nThis object is created internally and returned from http.request(). It\nrepresents an in-progress request whose header has already been queued. The\nheader is still mutable using the setHeader(name, value),\ngetHeader(name), removeHeader(name) API. The actual header will\nbe sent along with the first data chunk or when calling request.end().
To get the response, add a listener for 'response' to the request object.\n'response' will be emitted from the request object when the response\nheaders have been received. The 'response' event is executed with one\nargument which is an instance of http.IncomingMessage.
During the 'response' event, one can add listeners to the\nresponse object; particularly to listen for the 'data' event.
If no 'response' handler is added, then the response will be\nentirely discarded. However, if a 'response' event handler is added,\nthen the data from the response object must be consumed, either by\ncalling response.read() whenever there is a 'readable' event, or\nby adding a 'data' handler, or by calling the .resume() method.\nUntil the data is consumed, the 'end' event will not fire. Also, until\nthe data is read it will consume memory that can eventually lead to a\n'process out of memory' error.
Node.js does not check whether Content-Length and the length of the\nbody which has been transmitted are equal or not.
\nThe request inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'abort'", "type": "event", "name": "abort", "meta": { "added": [ "v1.4.1" ], "changes": [] }, "params": [], "desc": "Emitted when the request has been aborted by the client. This event is only\nemitted on the first call to abort().
Emitted each time a server responds to a request with a CONNECT method. If\nthis event is not being listened for, clients receiving a CONNECT method will\nhave their connections closed.
A client and server pair demonstrating how to listen for the 'connect' event:
const http = require('http');\nconst net = require('net');\nconst url = require('url');\n\n// Create an HTTP tunneling proxy\nconst proxy = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nproxy.on('connect', (req, cltSocket, head) => {\n // connect to an origin server\n const srvUrl = url.parse(`http://${req.url}`);\n const srvSocket = net.connect(srvUrl.port, srvUrl.hostname, () => {\n cltSocket.write('HTTP/1.1 200 Connection Established\\r\\n' +\n 'Proxy-agent: Node.js-Proxy\\r\\n' +\n '\\r\\n');\n srvSocket.write(head);\n srvSocket.pipe(cltSocket);\n cltSocket.pipe(srvSocket);\n });\n});\n\n// now that proxy is running\nproxy.listen(1337, '127.0.0.1', () => {\n\n // make a request to a tunneling proxy\n const options = {\n port: 1337,\n host: '127.0.0.1',\n method: 'CONNECT',\n path: 'www.google.com:80'\n };\n\n const req = http.request(options);\n req.end();\n\n req.on('connect', (res, socket, head) => {\n console.log('got connected!');\n\n // make a request over an HTTP tunnel\n socket.write('GET / HTTP/1.1\\r\\n' +\n 'Host: www.google.com:80\\r\\n' +\n 'Connection: close\\r\\n' +\n '\\r\\n');\n socket.on('data', (chunk) => {\n console.log(chunk.toString());\n });\n socket.on('end', () => {\n proxy.close();\n });\n });\n});\nEmitted when the server sends a '100 Continue' HTTP response, usually because\nthe request contained 'Expect: 100-continue'. This is an instruction that\nthe client should send the request body.
" }, { "textRaw": "Event: 'information'", "type": "event", "name": "information", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "params": [], "desc": "Emitted when the server sends a 1xx response (excluding 101 Upgrade). This\nevent is emitted with a callback containing an object with a status code.
\nconst http = require('http');\n\nconst options = {\n host: '127.0.0.1',\n port: 8080,\n path: '/length_request'\n};\n\n// Make a request\nconst req = http.request(options);\nreq.end();\n\nreq.on('information', (res) => {\n console.log(`Got information prior to main response: ${res.statusCode}`);\n});\n101 Upgrade statuses do not fire this event due to their break from the\ntraditional HTTP request/response chain, such as web sockets, in-place TLS\nupgrades, or HTTP 2.0. To be notified of 101 Upgrade notices, listen for the\n'upgrade' event instead.
Emitted when a response is received to this request. This event is emitted only\nonce.
" }, { "textRaw": "Event: 'socket'", "type": "event", "name": "socket", "meta": { "added": [ "v0.5.3" ], "changes": [] }, "params": [ { "textRaw": "`socket` {net.Socket}", "name": "socket", "type": "net.Socket" } ], "desc": "Emitted after a socket is assigned to this request.
" }, { "textRaw": "Event: 'timeout'", "type": "event", "name": "timeout", "meta": { "added": [ "v0.7.8" ], "changes": [] }, "params": [], "desc": "Emitted when the underlying socket times out from inactivity. This only notifies\nthat the socket has been idle. The request must be aborted manually.
\nSee also: request.setTimeout().
Emitted each time a server responds to a request with an upgrade. If this\nevent is not being listened for and the response status code is 101 Switching\nProtocols, clients receiving an upgrade header will have their connections\nclosed.
\nA client server pair demonstrating how to listen for the 'upgrade' event.
const http = require('http');\n\n// Create an HTTP server\nconst srv = http.createServer((req, res) => {\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('okay');\n});\nsrv.on('upgrade', (req, socket, head) => {\n socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\\r\\n' +\n 'Upgrade: WebSocket\\r\\n' +\n 'Connection: Upgrade\\r\\n' +\n '\\r\\n');\n\n socket.pipe(socket); // echo back\n});\n\n// now that server is running\nsrv.listen(1337, '127.0.0.1', () => {\n\n // make a request\n const options = {\n port: 1337,\n host: '127.0.0.1',\n headers: {\n 'Connection': 'Upgrade',\n 'Upgrade': 'websocket'\n }\n };\n\n const req = http.request(options);\n req.end();\n\n req.on('upgrade', (res, socket, upgradeHead) => {\n console.log('got upgraded!');\n socket.end();\n process.exit(0);\n });\n});\nMarks the request as aborting. Calling this will cause remaining data\nin the response to be dropped and the socket to be destroyed.
" }, { "textRaw": "request.end([data[, encoding]][, callback])", "type": "method", "name": "end", "meta": { "added": [ "v0.1.90" ], "changes": [ { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/18780", "description": "This method now returns a reference to `ClientRequest`." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {this}", "name": "return", "type": "this" }, "params": [ { "textRaw": "`data` {string|Buffer}", "name": "data", "type": "string|Buffer", "optional": true }, { "textRaw": "`encoding` {string}", "name": "encoding", "type": "string", "optional": true }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function", "optional": true } ] } ], "desc": "Finishes sending the request. If any parts of the body are\nunsent, it will flush them to the stream. If the request is\nchunked, this will send the terminating '0\\r\\n\\r\\n'.
If data is specified, it is equivalent to calling\nrequest.write(data, encoding) followed by request.end(callback).
If callback is specified, it will be called when the request stream\nis finished.
Flush the request headers.
\nFor efficiency reasons, Node.js normally buffers the request headers until\nrequest.end() is called or the first chunk of request data is written. It\nthen tries to pack the request headers and data into a single TCP packet.
That's usually desired (it saves a TCP round-trip), but not when the first\ndata is not sent until possibly much later. request.flushHeaders() bypasses\nthe optimization and kickstarts the request.
Reads out a header on the request. Note that the name is case insensitive.\nThe type of the return value depends on the arguments provided to\nrequest.setHeader().
request.setHeader('content-type', 'text/html');\nrequest.setHeader('Content-Length', Buffer.byteLength(body));\nrequest.setHeader('Cookie', ['type=ninja', 'language=javascript']);\nconst contentType = request.getHeader('Content-Type');\n// contentType is 'text/html'\nconst contentLength = request.getHeader('Content-Length');\n// contentLength is of type number\nconst cookie = request.getHeader('Cookie');\n// cookie is of type string[]\nRemoves a header that's already defined into headers object.
\nrequest.removeHeader('Content-Type');\nSets a single header value for headers object. If this header already exists in\nthe to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name. Non-string values will be\nstored without modification. Therefore, request.getHeader() may return\nnon-string values. However, the non-string values will be converted to strings\nfor network transmission.
request.setHeader('Content-Type', 'application/json');\nor
\nrequest.setHeader('Cookie', ['type=ninja', 'language=javascript']);\nOnce a socket is assigned to this request and is connected\nsocket.setNoDelay() will be called.
Once a socket is assigned to this request and is connected\nsocket.setKeepAlive() will be called.
Once a socket is assigned to this request and is connected\nsocket.setTimeout() will be called.
Sends a chunk of the body. By calling this method\nmany times, a request body can be sent to a\nserver — in that case it is suggested to use the\n['Transfer-Encoding', 'chunked'] header line when\ncreating the request.
The encoding argument is optional and only applies when chunk is a string.\nDefaults to 'utf8'.
The callback argument is optional and will be called when this chunk of data\nis flushed, but only if the chunk is non-empty.
Returns true if the entire data was flushed successfully to the kernel\nbuffer. Returns false if all or part of the data was queued in user memory.\n'drain' will be emitted when the buffer is free again.
When write function is called with empty string or buffer, it does\nnothing and waits for more input.
If a request has been aborted, this value is the time when the request was\naborted, in milliseconds since 1 January 1970 00:00:00 UTC.
" }, { "textRaw": "`connection` {net.Socket}", "type": "net.Socket", "name": "connection", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "See request.socket.
The request.finished property will be true if request.end()\nhas been called. request.end() will automatically be called if the\nrequest was initiated via http.get().
Limits maximum response headers count. If set to 0, no limit will be applied.
" }, { "textRaw": "`socket` {net.Socket}", "type": "net.Socket", "name": "socket", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "Reference to the underlying socket. Usually users will not want to access\nthis property. In particular, the socket will not emit 'readable' events\nbecause of how the protocol parser attaches to the socket. The socket\nmay also be accessed via request.connection.
const http = require('http');\nconst options = {\n host: 'www.google.com',\n};\nconst req = http.get(options);\nreq.end();\nreq.once('response', (res) => {\n const ip = req.socket.localAddress;\n const port = req.socket.localPort;\n console.log(`Your IP address is ${ip} and your source port is ${port}.`);\n // consume response object\n});\nThis class inherits from net.Server and has the following additional\nevents:
Emitted each time a request with an HTTP Expect: 100-continue is received.\nIf this event is not listened for, the server will automatically respond\nwith a 100 Continue as appropriate.
Handling this event involves calling response.writeContinue() if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
Note that when this event is emitted and handled, the 'request' event will\nnot be emitted.
Emitted each time a request with an HTTP Expect header is received, where the\nvalue is not 100-continue. If this event is not listened for, the server will\nautomatically respond with a 417 Expectation Failed as appropriate.
Note that when this event is emitted and handled, the 'request' event will\nnot be emitted.
If a client connection emits an 'error' event, it will be forwarded here.\nListener of this event is responsible for closing/destroying the underlying\nsocket. For example, one may wish to more gracefully close the socket with a\ncustom HTTP response instead of abruptly severing the connection.
Default behavior is to close the socket with an HTTP '400 Bad Request' response\nif possible, otherwise the socket is immediately destroyed.
\nsocket is the net.Socket object that the error originated from.
const http = require('http');\n\nconst server = http.createServer((req, res) => {\n res.end();\n});\nserver.on('clientError', (err, socket) => {\n socket.end('HTTP/1.1 400 Bad Request\\r\\n\\r\\n');\n});\nserver.listen(8000);\nWhen the 'clientError' event occurs, there is no request or response\nobject, so any HTTP response sent, including response headers and payload,\nmust be written directly to the socket object. Care must be taken to\nensure the response is a properly formatted HTTP response message.
err is an instance of Error with two extra columns:
bytesParsed: the bytes count of request packet that Node.js may have parsed\ncorrectly;rawPacket: the raw packet of current request.Emitted when the server closes.
" }, { "textRaw": "Event: 'connect'", "type": "event", "name": "connect", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "params": [ { "textRaw": "`request` {http.IncomingMessage} Arguments for the HTTP request, as it is in the [`'request'`][] event", "name": "request", "type": "http.IncomingMessage", "desc": "Arguments for the HTTP request, as it is in the [`'request'`][] event" }, { "textRaw": "`socket` {net.Socket} Network socket between the server and client", "name": "socket", "type": "net.Socket", "desc": "Network socket between the server and client" }, { "textRaw": "`head` {Buffer} The first packet of the tunneling stream (may be empty)", "name": "head", "type": "Buffer", "desc": "The first packet of the tunneling stream (may be empty)" } ], "desc": "Emitted each time a client requests an HTTP CONNECT method. If this event is\nnot listened for, then clients requesting a CONNECT method will have their\nconnections closed.
After this event is emitted, the request's socket will not have a 'data'\nevent listener, meaning it will need to be bound in order to handle data\nsent to the server on that socket.
This event is emitted when a new TCP stream is established. socket is\ntypically an object of type net.Socket. Usually users will not want to\naccess this event. In particular, the socket will not emit 'readable' events\nbecause of how the protocol parser attaches to the socket. The socket can\nalso be accessed at request.connection.
This event can also be explicitly emitted by users to inject connections\ninto the HTTP server. In that case, any Duplex stream can be passed.
Emitted each time there is a request. Note that there may be multiple requests\nper connection (in the case of HTTP Keep-Alive connections).
" }, { "textRaw": "Event: 'upgrade'", "type": "event", "name": "upgrade", "meta": { "added": [ "v0.1.94" ], "changes": [ { "version": "v10.0.0", "pr-url": "v10.0.0", "description": "Not listening to this event no longer causes the socket to be destroyed if a client sends an Upgrade header." } ] }, "params": [ { "textRaw": "`request` {http.IncomingMessage} Arguments for the HTTP request, as it is in the [`'request'`][] event", "name": "request", "type": "http.IncomingMessage", "desc": "Arguments for the HTTP request, as it is in the [`'request'`][] event" }, { "textRaw": "`socket` {net.Socket} Network socket between the server and client", "name": "socket", "type": "net.Socket", "desc": "Network socket between the server and client" }, { "textRaw": "`head` {Buffer} The first packet of the upgraded stream (may be empty)", "name": "head", "type": "Buffer", "desc": "The first packet of the upgraded stream (may be empty)" } ], "desc": "Emitted each time a client requests an HTTP upgrade. Listening to this event\nis optional and clients cannot insist on a protocol change.
\nAfter this event is emitted, the request's socket will not have a 'data'\nevent listener, meaning it will need to be bound in order to handle data\nsent to the server on that socket.
Stops the server from accepting new connections. See net.Server.close().
Starts the HTTP server listening for connections.\nThis method is identical to server.listen() from net.Server.
Sets the timeout value for sockets, and emits a 'timeout' event on\nthe Server object, passing the socket as an argument, if a timeout\noccurs.
If there is a 'timeout' event listener on the Server object, then it\nwill be called with the timed-out socket as an argument.
By default, the Server's timeout value is 2 minutes, and sockets are\ndestroyed automatically if they time out. However, if a callback is assigned\nto the Server's 'timeout' event, timeouts must be handled explicitly.
Limits maximum incoming headers count. If set to 0, no limit will be applied.
" }, { "textRaw": "`headersTimeout` {number} **Default:** `40000`", "type": "number", "name": "headersTimeout", "meta": { "added": [ "v10.14.0" ], "changes": [] }, "default": "`40000`", "desc": "Limit the amount of time the parser will wait to receive the complete HTTP\nheaders.
\nIn case of inactivity, the rules defined in [server.timeout][] apply. However,\nthat inactivity based timeout would still allow the connection to be kept open\nif the headers are being sent very slowly (by default, up to a byte per 2\nminutes). In order to prevent this, whenever header data arrives an additional\ncheck is made that more than server.headersTimeout milliseconds has not\npassed since the connection was established. If the check fails, a 'timeout'\nevent is emitted on the server object, and (by default) the socket is destroyed.\nSee [server.timeout][] for more information on how timeout behaviour can be\ncustomised.
The number of milliseconds of inactivity before a socket is presumed\nto have timed out.
\nA value of 0 will disable the timeout behavior on incoming connections.
The socket timeout logic is set up on connection, so changing this\nvalue only affects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." }, { "textRaw": "`keepAliveTimeout` {number} Timeout in milliseconds. **Default:** `5000` (5 seconds).", "type": "number", "name": "keepAliveTimeout", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "default": "`5000` (5 seconds)", "desc": "The number of milliseconds of inactivity a server needs to wait for additional\nincoming data, after it has finished writing the last response, before a socket\nwill be destroyed. If the server receives new data before the keep-alive\ntimeout has fired, it will reset the regular inactivity timeout, i.e.,\nserver.timeout.
A value of 0 will disable the keep-alive timeout behavior on incoming\nconnections.\nA value of 0 makes the http server behave similarly to Node.js versions prior\nto 8.0.0, which did not have a keep-alive timeout.
The socket timeout logic is set up on connection, so changing this value only\naffects new connections to the server, not any existing connections.
", "shortDesc": "Timeout in milliseconds." } ] }, { "textRaw": "Class: http.ServerResponse", "type": "class", "name": "http.ServerResponse", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "This object is created internally by an HTTP server — not by the user. It is\npassed as the second parameter to the 'request' event.
The response inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v0.6.7" ], "changes": [] }, "params": [], "desc": "Indicates that the underlying connection was terminated before\nresponse.end() was called or able to flush.
Emitted when the response has been sent. More specifically, this event is\nemitted when the last segment of the response headers and body have been\nhanded off to the operating system for transmission over the network. It\ndoes not imply that the client has received anything yet.
" } ], "methods": [ { "textRaw": "response.addTrailers(headers)", "type": "method", "name": "addTrailers", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`headers` {Object}", "name": "headers", "type": "Object" } ] } ], "desc": "This method adds HTTP trailing headers (a header but at the end of the\nmessage) to the response.
\nTrailers will only be emitted if chunked encoding is used for the\nresponse; if it is not (e.g. if the request was HTTP/1.0), they will\nbe silently discarded.
\nNote that HTTP requires the Trailer header to be sent in order to\nemit trailers, with a list of the header fields in its value. E.g.,
response.writeHead(200, { 'Content-Type': 'text/plain',\n 'Trailer': 'Content-MD5' });\nresponse.write(fileData);\nresponse.addTrailers({ 'Content-MD5': '7895bf4b8828b55ceaf47747b4bca667' });\nresponse.end();\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
This method signals to the server that all of the response headers and body\nhave been sent; that server should consider this message complete.\nThe method, response.end(), MUST be called on each response.
If data is specified, it is similar in effect to calling\nresponse.write(data, encoding) followed by response.end(callback).
If callback is specified, it will be called when the response stream\nis finished.
Reads out a header that's already been queued but not sent to the client.\nNote that the name is case insensitive. The type of the return value depends\non the arguments provided to response.setHeader().
response.setHeader('Content-Type', 'text/html');\nresponse.setHeader('Content-Length', Buffer.byteLength(body));\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\nconst contentType = response.getHeader('content-type');\n// contentType is 'text/html'\nconst contentLength = response.getHeader('Content-Length');\n// contentLength is of type number\nconst setCookie = response.getHeader('set-cookie');\n// setCookie is of type string[]\nReturns an array containing the unique names of the current outgoing headers.\nAll header names are lowercase.
\nresponse.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = response.getHeaderNames();\n// headerNames === ['foo', 'set-cookie']\nReturns a shallow copy of the current outgoing headers. Since a shallow copy\nis used, array values may be mutated without additional calls to various\nheader-related http module methods. The keys of the returned object are the\nheader names and the values are the respective header values. All header names\nare lowercase.
\nThe object returned by the response.getHeaders() method does not\nprototypically inherit from the JavaScript Object. This means that typical\nObject methods such as obj.toString(), obj.hasOwnProperty(), and others\nare not defined and will not work.
response.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = response.getHeaders();\n// headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }\nReturns true if the header identified by name is currently set in the\noutgoing headers. Note that the header name matching is case-insensitive.
const hasContentType = response.hasHeader('content-type');\nRemoves a header that's queued for implicit sending.
\nresponse.removeHeader('Content-Encoding');\nSets a single header value for implicit headers. If this header already exists\nin the to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name. Non-string values will be\nstored without modification. Therefore, response.getHeader() may return\nnon-string values. However, the non-string values will be converted to strings\nfor network transmission.
response.setHeader('Content-Type', 'text/html');\nor
\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
When headers have been set with response.setHeader(), they will be merged\nwith any headers passed to response.writeHead(), with the headers passed\nto response.writeHead() given precedence.
// returns content-type = text/plain\nconst server = http.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\nIf response.writeHead() method is called and this method has not been\ncalled, it will directly write the supplied header values onto the network\nchannel without caching internally, and the response.getHeader() on the\nheader will not yield the expected result. If progressive population of headers\nis desired with potential future retrieval and modification, use\nresponse.setHeader() instead of response.writeHead().
Sets the Socket's timeout value to msecs. If a callback is\nprovided, then it is added as a listener on the 'timeout' event on\nthe response object.
If no 'timeout' listener is added to the request, the response, or\nthe server, then sockets are destroyed when they time out. If a handler is\nassigned to the request, the response, or the server's 'timeout' events,\ntimed out sockets must be handled explicitly.
If this method is called and response.writeHead() has not been called,\nit will switch to implicit header mode and flush the implicit headers.
This sends a chunk of the response body. This method may\nbe called multiple times to provide successive parts of the body.
\nNote that in the http module, the response body is omitted when the\nrequest is a HEAD request. Similarly, the 204 and 304 responses\nmust not include a message body.
chunk can be a string or a buffer. If chunk is a string,\nthe second parameter specifies how to encode it into a byte stream.\ncallback will be called when this chunk of data is flushed.
This is the raw HTTP body and has nothing to do with higher-level multi-part\nbody encodings that may be used.
\nThe first time response.write() is called, it will send the buffered\nheader information and the first chunk of the body to the client. The second\ntime response.write() is called, Node.js assumes data will be streamed,\nand sends the new data separately. That is, the response is buffered up to the\nfirst chunk of the body.
Returns true if the entire data was flushed successfully to the kernel\nbuffer. Returns false if all or part of the data was queued in user memory.\n'drain' will be emitted when the buffer is free again.
Sends a HTTP/1.1 100 Continue message to the client, indicating that\nthe request body should be sent. See the 'checkContinue' event on\nServer.
Sends a response header to the request. The status code is a 3-digit HTTP\nstatus code, like 404. The last argument, headers, are the response headers.\nOptionally one can give a human-readable statusMessage as the second\nargument.
Returns a reference to the ServerResponse, so that calls can be chained.
const body = 'hello world';\nresponse\n .writeHead(200, {\n 'Content-Length': Buffer.byteLength(body),\n 'Content-Type': 'text/plain'\n })\n .end(body);\nThis method must only be called once on a message and it must\nbe called before response.end() is called.
If response.write() or response.end() are called before calling\nthis, the implicit/mutable headers will be calculated and call this function.
When headers have been set with response.setHeader(), they will be merged\nwith any headers passed to response.writeHead(), with the headers passed\nto response.writeHead() given precedence.
If this method is called and response.setHeader() has not been called,\nit will directly write the supplied header values onto the network channel\nwithout caching internally, and the response.getHeader() on the header\nwill not yield the expected result. If progressive population of headers is\ndesired with potential future retrieval and modification, use\nresponse.setHeader() instead.
// returns content-type = text/plain\nconst server = http.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\nNote that Content-Length is given in bytes not characters. The above example\nworks because the string 'hello world' contains only single byte characters.\nIf the body contains higher coded characters then Buffer.byteLength()\nshould be used to determine the number of bytes in a given encoding.\nAnd Node.js does not check whether Content-Length and the length of the body\nwhich has been transmitted are equal or not.
Attempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
Sends a HTTP/1.1 102 Processing message to the client, indicating that\nthe request body should be sent.
" } ], "properties": [ { "textRaw": "`connection` {net.Socket}", "type": "net.Socket", "name": "connection", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "See response.socket.
Boolean value that indicates whether the response has completed. Starts\nas false. After response.end() executes, the value will be true.
Boolean (read-only). True if headers were sent, false otherwise.
" }, { "textRaw": "`sendDate` {boolean}", "type": "boolean", "name": "sendDate", "meta": { "added": [ "v0.7.5" ], "changes": [] }, "desc": "When true, the Date header will be automatically generated and sent in\nthe response if it is not already present in the headers. Defaults to true.
\nThis should only be disabled for testing; HTTP requires the Date header\nin responses.
" }, { "textRaw": "`socket` {net.Socket}", "type": "net.Socket", "name": "socket", "meta": { "added": [ "v0.3.0" ], "changes": [] }, "desc": "Reference to the underlying socket. Usually users will not want to access\nthis property. In particular, the socket will not emit 'readable' events\nbecause of how the protocol parser attaches to the socket. After\nresponse.end(), the property is nulled. The socket may also be accessed\nvia response.connection.
const http = require('http');\nconst server = http.createServer((req, res) => {\n const ip = res.socket.remoteAddress;\n const port = res.socket.remotePort;\n res.end(`Your IP address is ${ip} and your source port is ${port}.`);\n}).listen(3000);\nWhen using implicit headers (not calling response.writeHead() explicitly),\nthis property controls the status code that will be sent to the client when\nthe headers get flushed.
response.statusCode = 404;\nAfter response header was sent to the client, this property indicates the\nstatus code which was sent out.
" }, { "textRaw": "`statusMessage` {string}", "type": "string", "name": "statusMessage", "meta": { "added": [ "v0.11.8" ], "changes": [] }, "desc": "When using implicit headers (not calling response.writeHead() explicitly),\nthis property controls the status message that will be sent to the client when\nthe headers get flushed. If this is left as undefined then the standard\nmessage for the status code will be used.
response.statusMessage = 'Not found';\nAfter response header was sent to the client, this property indicates the\nstatus message which was sent out.
" } ] }, { "textRaw": "Class: http.IncomingMessage", "type": "class", "name": "http.IncomingMessage", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "An IncomingMessage object is created by http.Server or\nhttp.ClientRequest and passed as the first argument to the 'request'\nand 'response' event respectively. It may be used to access response\nstatus, headers and data.
It implements the Readable Stream interface, as well as the\nfollowing additional events, methods, and properties.
", "events": [ { "textRaw": "Event: 'aborted'", "type": "event", "name": "aborted", "meta": { "added": [ "v0.3.8" ], "changes": [] }, "params": [], "desc": "Emitted when the request has been aborted.
" }, { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v0.4.2" ], "changes": [] }, "params": [], "desc": "Indicates that the underlying connection was closed.\nJust like 'end', this event occurs only once per response.
The message.aborted property will be true if the request has\nbeen aborted.
The message.complete property will be true if a complete HTTP message has\nbeen received and successfully parsed.
This property is particularly useful as a means of determining if a client or\nserver fully transmitted a message before a connection was terminated:
\nconst req = http.request({\n host: '127.0.0.1',\n port: 8080,\n method: 'POST'\n}, (res) => {\n res.resume();\n res.on('end', () => {\n if (!res.complete)\n console.error(\n 'The connection was terminated while the message was still being sent');\n });\n});\nThe request/response headers object.
\nKey-value pairs of header names and values. Header names are lower-cased.
\n// Prints something like:\n//\n// { 'user-agent': 'curl/7.22.0',\n// host: '127.0.0.1:8000',\n// accept: '*/*' }\nconsole.log(request.headers);\nDuplicates in raw headers are handled in the following ways, depending on the\nheader name:
\nage, authorization, content-length, content-type,\netag, expires, from, host, if-modified-since, if-unmodified-since,\nlast-modified, location, max-forwards, proxy-authorization, referer,\nretry-after, or user-agent are discarded.set-cookie is always an array. Duplicates are added to the array.cookie headers, the values are joined together with '; '.In case of server request, the HTTP version sent by the client. In the case of\nclient response, the HTTP version of the connected-to server.\nProbably either '1.1' or '1.0'.
Also message.httpVersionMajor is the first integer and\nmessage.httpVersionMinor is the second.
Only valid for request obtained from http.Server.
The request method as a string. Read only. Examples: 'GET', 'DELETE'.
The raw request/response headers list exactly as they were received.
\nNote that the keys and values are in the same list. It is not a\nlist of tuples. So, the even-numbered offsets are key values, and the\nodd-numbered offsets are the associated values.
\nHeader names are not lowercased, and duplicates are not merged.
\n// Prints something like:\n//\n// [ 'user-agent',\n// 'this is invalid because there can be only one',\n// 'User-Agent',\n// 'curl/7.22.0',\n// 'Host',\n// '127.0.0.1:8000',\n// 'ACCEPT',\n// '*/*' ]\nconsole.log(request.rawHeaders);\nThe raw request/response trailer keys and values exactly as they were\nreceived. Only populated at the 'end' event.
The net.Socket object associated with the connection.
With HTTPS support, use request.socket.getPeerCertificate() to obtain the\nclient's authentication details.
Only valid for response obtained from http.ClientRequest.
The 3-digit HTTP response status code. E.G. 404.
Only valid for response obtained from http.ClientRequest.
The HTTP response status message (reason phrase). E.G. OK or Internal Server Error.
The request/response trailers object. Only populated at the 'end' event.
Only valid for request obtained from http.Server.
Request URL string. This contains only the URL that is\npresent in the actual HTTP request. If the request is:
\nGET /status?name=ryan HTTP/1.1\\r\\n\nAccept: text/plain\\r\\n\n\\r\\n\nThen request.url will be:
'/status?name=ryan'\nTo parse the url into its parts require('url').parse(request.url)\ncan be used:
$ node\n> require('url').parse('/status?name=ryan')\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: 'name=ryan',\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\nTo extract the parameters from the query string, the\nrequire('querystring').parse function can be used, or\ntrue can be passed as the second argument to require('url').parse:
$ node\n> require('url').parse('/status?name=ryan', true)\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: { name: 'ryan' },\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\nCalls destroy() on the socket that received the IncomingMessage. If error\nis provided, an 'error' event is emitted and error is passed as an argument\nto any listeners on the event.
Calls message.connection.setTimeout(msecs, callback).
A list of the HTTP methods that are supported by the parser.
" }, { "textRaw": "`STATUS_CODES` {Object}", "type": "Object", "name": "STATUS_CODES", "meta": { "added": [ "v0.1.22" ], "changes": [] }, "desc": "A collection of all the standard HTTP response status codes, and the\nshort description of each. For example, http.STATUS_CODES[404] === 'Not Found'.
Global instance of Agent which is used as the default for all HTTP client\nrequests.
Read-only property specifying the maximum allowed size of HTTP headers in bytes.\nDefaults to 8KB. Configurable using the --max-http-header-size CLI option.
Returns a new instance of http.Server.
The requestListener is a function which is automatically\nadded to the 'request' event.
Since most requests are GET requests without bodies, Node.js provides this\nconvenience method. The only difference between this method and\nhttp.request() is that it sets the method to GET and calls req.end()\nautomatically. Note that the callback must take care to consume the response\ndata for reasons stated in http.ClientRequest section.
The callback is invoked with a single argument that is an instance of\nhttp.IncomingMessage.
JSON fetching example:
\nhttp.get('http://nodejs.org/dist/index.json', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\n if (statusCode !== 200) {\n error = new Error('Request Failed.\\n' +\n `Status Code: ${statusCode}`);\n } else if (!/^application\\/json/.test(contentType)) {\n error = new Error('Invalid content-type.\\n' +\n `Expected application/json but received ${contentType}`);\n }\n if (error) {\n console.error(error.message);\n // consume response data to free up memory\n res.resume();\n return;\n }\n\n res.setEncoding('utf8');\n let rawData = '';\n res.on('data', (chunk) => { rawData += chunk; });\n res.on('end', () => {\n try {\n const parsedData = JSON.parse(rawData);\n console.log(parsedData);\n } catch (e) {\n console.error(e.message);\n }\n });\n}).on('error', (e) => {\n console.error(`Got error: ${e.message}`);\n});\nSince most requests are GET requests without bodies, Node.js provides this\nconvenience method. The only difference between this method and\nhttp.request() is that it sets the method to GET and calls req.end()\nautomatically. Note that the callback must take care to consume the response\ndata for reasons stated in http.ClientRequest section.
The callback is invoked with a single argument that is an instance of\nhttp.IncomingMessage.
JSON fetching example:
\nhttp.get('http://nodejs.org/dist/index.json', (res) => {\n const { statusCode } = res;\n const contentType = res.headers['content-type'];\n\n let error;\n if (statusCode !== 200) {\n error = new Error('Request Failed.\\n' +\n `Status Code: ${statusCode}`);\n } else if (!/^application\\/json/.test(contentType)) {\n error = new Error('Invalid content-type.\\n' +\n `Expected application/json but received ${contentType}`);\n }\n if (error) {\n console.error(error.message);\n // consume response data to free up memory\n res.resume();\n return;\n }\n\n res.setEncoding('utf8');\n let rawData = '';\n res.on('data', (chunk) => { rawData += chunk; });\n res.on('end', () => {\n try {\n const parsedData = JSON.parse(rawData);\n console.log(parsedData);\n } catch (e) {\n console.error(e.message);\n }\n });\n}).on('error', (e) => {\n console.error(`Got error: ${e.message}`);\n});\nNode.js maintains several connections per server to make HTTP requests.\nThis function allows one to transparently issue requests.
\nurl can be a string or a URL object. If url is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
If both url and options are specified, the objects are merged, with the\noptions properties taking precedence.
The optional callback parameter will be added as a one-time listener for\nthe 'response' event.
http.request() returns an instance of the http.ClientRequest\nclass. The ClientRequest instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest object.
const postData = querystring.stringify({\n 'msg': 'Hello World!'\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/x-www-form-urlencoded',\n 'Content-Length': Buffer.byteLength(postData)\n }\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// write data to request body\nreq.write(postData);\nreq.end();\nNote that in the example req.end() was called. With http.request() one\nmust always call req.end() to signify the end of the request -\neven if there is no data being written to the request body.
If any error is encountered during the request (be that with DNS resolution,\nTCP level errors, or actual HTTP parse errors) an 'error' event is emitted\non the returned request object. As with all 'error' events, if no listeners\nare registered the error will be thrown.
There are a few special headers that should be noted.
\nSending a 'Connection: keep-alive' will notify Node.js that the connection to\nthe server should be persisted until the next request.
\nSending a 'Content-Length' header will disable the default chunked encoding.
\nSending an 'Expect' header will immediately send the request headers.\nUsually, when sending 'Expect: 100-continue', both a timeout and a listener\nfor the 'continue' event should be set. See RFC2616 Section 8.2.3 for more\ninformation.
Sending an Authorization header will override using the auth option\nto compute basic authentication.
Example using a URL as options:
const options = new URL('http://abc:xyz@example.com');\n\nconst req = http.request(options, (res) => {\n // ...\n});\nIn a successful request, the following events will be emitted in the following\norder:
\n'socket''response'
'data' any number of times, on the res object\n('data' will not be emitted at all if the response body is empty, for\ninstance, in most redirects)'end' on the res object'close'In the case of a connection error, the following events will be emitted:
\n'socket''error''close'If req.abort() is called before the connection succeeds, the following events\nwill be emitted in the following order:
'socket'req.abort() called here)'abort''error' with an error with message 'Error: socket hang up' and code\n'ECONNRESET''close'If req.abort() is called after the response is received, the following events\nwill be emitted in the following order:
'socket''response'
'data' any number of times, on the res objectreq.abort() called here)'abort''aborted' on the res object'close''end' on the res object'close' on the res objectNote that setting the timeout option or using the setTimeout() function will\nnot abort the request or do anything besides add a 'timeout' event.
Node.js maintains several connections per server to make HTTP requests.\nThis function allows one to transparently issue requests.
\nurl can be a string or a URL object. If url is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
If both url and options are specified, the objects are merged, with the\noptions properties taking precedence.
The optional callback parameter will be added as a one-time listener for\nthe 'response' event.
http.request() returns an instance of the http.ClientRequest\nclass. The ClientRequest instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest object.
const postData = querystring.stringify({\n 'msg': 'Hello World!'\n});\n\nconst options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/x-www-form-urlencoded',\n 'Content-Length': Buffer.byteLength(postData)\n }\n};\n\nconst req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.');\n });\n});\n\nreq.on('error', (e) => {\n console.error(`problem with request: ${e.message}`);\n});\n\n// write data to request body\nreq.write(postData);\nreq.end();\nNote that in the example req.end() was called. With http.request() one\nmust always call req.end() to signify the end of the request -\neven if there is no data being written to the request body.
If any error is encountered during the request (be that with DNS resolution,\nTCP level errors, or actual HTTP parse errors) an 'error' event is emitted\non the returned request object. As with all 'error' events, if no listeners\nare registered the error will be thrown.
There are a few special headers that should be noted.
\nSending a 'Connection: keep-alive' will notify Node.js that the connection to\nthe server should be persisted until the next request.
\nSending a 'Content-Length' header will disable the default chunked encoding.
\nSending an 'Expect' header will immediately send the request headers.\nUsually, when sending 'Expect: 100-continue', both a timeout and a listener\nfor the 'continue' event should be set. See RFC2616 Section 8.2.3 for more\ninformation.
Sending an Authorization header will override using the auth option\nto compute basic authentication.
Example using a URL as options:
const options = new URL('http://abc:xyz@example.com');\n\nconst req = http.request(options, (res) => {\n // ...\n});\nIn a successful request, the following events will be emitted in the following\norder:
\n'socket''response'
'data' any number of times, on the res object\n('data' will not be emitted at all if the response body is empty, for\ninstance, in most redirects)'end' on the res object'close'In the case of a connection error, the following events will be emitted:
\n'socket''error''close'If req.abort() is called before the connection succeeds, the following events\nwill be emitted in the following order:
'socket'req.abort() called here)'abort''error' with an error with message 'Error: socket hang up' and code\n'ECONNRESET''close'If req.abort() is called after the response is received, the following events\nwill be emitted in the following order:
'socket''response'
'data' any number of times, on the res objectreq.abort() called here)'abort''aborted' on the res object'close''end' on the res object'close' on the res objectNote that setting the timeout option or using the setTimeout() function will\nnot abort the request or do anything besides add a 'timeout' event.
The http2 module provides an implementation of the HTTP/2 protocol. It\ncan be accessed using:
const http2 = require('http2');\nThe Core API provides a low-level interface designed specifically around\nsupport for HTTP/2 protocol features. It is specifically not designed for\ncompatibility with the existing HTTP/1 module API. However,\nthe Compatibility API is.
\nThe http2 Core API is much more symmetric between client and server than the\nhttp API. For instance, most events, like 'error', 'connect' and\n'stream', can be emitted either by client-side code or server-side code.
The following illustrates a simple HTTP/2 server using the Core API.\nSince there are no browsers known that support\nunencrypted HTTP/2, the use of\nhttp2.createSecureServer() is necessary when communicating\nwith browser clients.
const http2 = require('http2');\nconst fs = require('fs');\n\nconst server = http2.createSecureServer({\n key: fs.readFileSync('localhost-privkey.pem'),\n cert: fs.readFileSync('localhost-cert.pem')\n});\nserver.on('error', (err) => console.error(err));\n\nserver.on('stream', (stream, headers) => {\n // stream is a Duplex\n stream.respond({\n 'content-type': 'text/html',\n ':status': 200\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(8443);\nTo generate the certificate and key for this example, run:
\nopenssl req -x509 -newkey rsa:2048 -nodes -sha256 -subj '/CN=localhost' \\\n -keyout localhost-privkey.pem -out localhost-cert.pem\nThe following illustrates an HTTP/2 client:
\nconst http2 = require('http2');\nconst fs = require('fs');\nconst client = http2.connect('https://localhost:8443', {\n ca: fs.readFileSync('localhost-cert.pem')\n});\nclient.on('error', (err) => console.error(err));\n\nconst req = client.request({ ':path': '/' });\n\nreq.on('response', (headers, flags) => {\n for (const name in headers) {\n console.log(`${name}: ${headers[name]}`);\n }\n});\n\nreq.setEncoding('utf8');\nlet data = '';\nreq.on('data', (chunk) => { data += chunk; });\nreq.on('end', () => {\n console.log(`\\n${data}`);\n client.close();\n});\nreq.end();\nHeaders are represented as own-properties on JavaScript objects. The property\nkeys will be serialized to lower-case. Property values should be strings (if\nthey are not they will be coerced to strings) or an Array of strings (in order\nto send more than one value per header field).
const headers = {\n ':status': '200',\n 'content-type': 'text-plain',\n 'ABC': ['has', 'more', 'than', 'one', 'value']\n};\n\nstream.respond(headers);\nHeader objects passed to callback functions will have a null prototype. This\nmeans that normal JavaScript object methods such as\nObject.prototype.toString() and Object.prototype.hasOwnProperty() will\nnot work.
For incoming headers:
\n:status header is converted to number.:status, :method, :authority, :scheme, :path,\n:protocol, age, authorization, access-control-allow-credentials,\naccess-control-max-age, access-control-request-method, content-encoding,\ncontent-language, content-length, content-location, content-md5,\ncontent-range, content-type, date, dnt, etag, expires, from,\nif-match, if-modified-since, if-none-match, if-range,\nif-unmodified-since, last-modified, location, max-forwards,\nproxy-authorization, range, referer,retry-after, tk,\nupgrade-insecure-requests, user-agent or x-content-type-options are\ndiscarded.set-cookie is always an array. Duplicates are added to the array.cookie headers, the values are joined together with '; '.const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream, headers) => {\n console.log(headers[':path']);\n console.log(headers.ABC);\n});\nThe http2.getDefaultSettings(), http2.getPackedSettings(),\nhttp2.createServer(), http2.createSecureServer(),\nhttp2session.settings(), http2session.localSettings, and\nhttp2session.remoteSettings APIs either return or receive as input an\nobject that defines configuration settings for an Http2Session object.\nThese objects are ordinary JavaScript objects containing the following\nproperties.
headerTableSize <number> Specifies the maximum number of bytes used for\nheader compression. The minimum allowed value is 0. The maximum allowed value\nis 232-1. Default: 4,096 octets.enablePush <boolean> Specifies true if HTTP/2 Push Streams are to be\npermitted on the Http2Session instances.initialWindowSize <number> Specifies the senders initial window size\nfor stream-level flow control. The minimum allowed value is 0. The maximum\nallowed value is 232-1. Default: 65,535 bytes.maxFrameSize <number> Specifies the size of the largest frame payload.\nThe minimum allowed value is 16,384. The maximum allowed value\nis 224-1. Default: 16,384 bytes.maxConcurrentStreams <number> Specifies the maximum number of concurrent\nstreams permitted on an Http2Session. There is no default value which\nimplies, at least theoretically, 231-1 streams may be open\nconcurrently at any given time in an Http2Session. The minimum value\nis 0. The maximum allowed value is 231-1.maxHeaderListSize <number> Specifies the maximum size (uncompressed octets)\nof header list that will be accepted. The minimum allowed value is 0. The\nmaximum allowed value is 232-1. Default: 65535.enableConnectProtocol<boolean> Specifies true if the \"Extended Connect\nProtocol\" defined by RFC 8441 is to be enabled. This setting is only\nmeaningful if sent by the server. Once the enableConnectProtocol setting\nhas been enabled for a given Http2Session, it cannot be disabled.All additional properties on the settings object are ignored.
", "type": "module", "displayName": "Settings Object" }, { "textRaw": "Using `options.selectPadding()`", "name": "using_`options.selectpadding()`", "desc": "When options.paddingStrategy is equal to\nhttp2.constants.PADDING_STRATEGY_CALLBACK, the HTTP/2 implementation will\nconsult the options.selectPadding() callback function, if provided, to\ndetermine the specific amount of padding to use per HEADERS and DATA frame.
The options.selectPadding() function receives two numeric arguments,\nframeLen and maxFrameLen and must return a number N such that\nframeLen <= N <= maxFrameLen.
const http2 = require('http2');\nconst server = http2.createServer({\n paddingStrategy: http2.constants.PADDING_STRATEGY_CALLBACK,\n selectPadding(frameLen, maxFrameLen) {\n return maxFrameLen;\n }\n});\nThe options.selectPadding() function is invoked once for every HEADERS and\nDATA frame. This has a definite noticeable impact on performance.
There are several types of error conditions that may arise when using the\nhttp2 module:
Validation errors occur when an incorrect argument, option, or setting value is\npassed in. These will always be reported by a synchronous throw.
State errors occur when an action is attempted at an incorrect time (for\ninstance, attempting to send data on a stream after it has closed). These will\nbe reported using either a synchronous throw or via an 'error' event on\nthe Http2Stream, Http2Session or HTTP/2 Server objects, depending on where\nand when the error occurs.
Internal errors occur when an HTTP/2 session fails unexpectedly. These will be\nreported via an 'error' event on the Http2Session or HTTP/2 Server objects.
Protocol errors occur when various HTTP/2 protocol constraints are violated.\nThese will be reported using either a synchronous throw or via an 'error'\nevent on the Http2Stream, Http2Session or HTTP/2 Server objects, depending\non where and when the error occurs.
The HTTP/2 implementation applies stricter handling of invalid characters in\nHTTP header names and values than the HTTP/1 implementation.
\nHeader field names are case-insensitive and are transmitted over the wire\nstrictly as lower-case strings. The API provided by Node.js allows header\nnames to be set as mixed-case strings (e.g. Content-Type) but will convert\nthose to lower-case (e.g. content-type) upon transmission.
Header field-names must only contain one or more of the following ASCII\ncharacters: a-z, A-Z, 0-9, !, #, $, %, &, ', *, +,\n-, ., ^, _, ` (backtick), |, and ~.
Using invalid characters within an HTTP header field name will cause the\nstream to be closed with a protocol error being reported.
\nHeader field values are handled with more leniency but should not contain\nnew-line or carriage return characters and should be limited to US-ASCII\ncharacters, per the requirements of the HTTP specification.
", "type": "module", "displayName": "Invalid character handling in header names and values" }, { "textRaw": "Push streams on the client", "name": "push_streams_on_the_client", "desc": "To receive pushed streams on the client, set a listener for the 'stream'\nevent on the ClientHttp2Session:
const http2 = require('http2');\n\nconst client = http2.connect('http://localhost');\n\nclient.on('stream', (pushedStream, requestHeaders) => {\n pushedStream.on('push', (responseHeaders) => {\n // process response headers\n });\n pushedStream.on('data', (chunk) => { /* handle pushed data */ });\n});\n\nconst req = client.request({ ':path': '/' });\nThe CONNECT method is used to allow an HTTP/2 server to be used as a proxy\nfor TCP/IP connections.
A simple TCP Server:
\nconst net = require('net');\n\nconst server = net.createServer((socket) => {\n let name = '';\n socket.setEncoding('utf8');\n socket.on('data', (chunk) => name += chunk);\n socket.on('end', () => socket.end(`hello ${name}`));\n});\n\nserver.listen(8000);\nAn HTTP/2 CONNECT proxy:
\nconst http2 = require('http2');\nconst { NGHTTP2_REFUSED_STREAM } = http2.constants;\nconst net = require('net');\n\nconst proxy = http2.createServer();\nproxy.on('stream', (stream, headers) => {\n if (headers[':method'] !== 'CONNECT') {\n // Only accept CONNECT requests\n stream.close(NGHTTP2_REFUSED_STREAM);\n return;\n }\n const auth = new URL(`tcp://${headers[':authority']}`);\n // It's a very good idea to verify that hostname and port are\n // things this proxy should be connecting to.\n const socket = net.connect(auth.port, auth.hostname, () => {\n stream.respond();\n socket.pipe(stream);\n stream.pipe(socket);\n });\n socket.on('error', (error) => {\n stream.close(http2.constants.NGHTTP2_CONNECT_ERROR);\n });\n});\n\nproxy.listen(8001);\nAn HTTP/2 CONNECT client:
\nconst http2 = require('http2');\n\nconst client = http2.connect('http://localhost:8001');\n\n// Must not specify the ':path' and ':scheme' headers\n// for CONNECT requests or an error will be thrown.\nconst req = client.request({\n ':method': 'CONNECT',\n ':authority': `localhost:${port}`\n});\n\nreq.on('response', (headers) => {\n console.log(headers[http2.constants.HTTP2_HEADER_STATUS]);\n});\nlet data = '';\nreq.setEncoding('utf8');\nreq.on('data', (chunk) => data += chunk);\nreq.on('end', () => {\n console.log(`The server says: ${data}`);\n client.close();\n});\nreq.end('Jane');\nRFC 8441 defines an \"Extended CONNECT Protocol\" extension to HTTP/2 that\nmay be used to bootstrap the use of an Http2Stream using the CONNECT\nmethod as a tunnel for other communication protocols (such as WebSockets).
The use of the Extended CONNECT Protocol is enabled by HTTP/2 servers by using\nthe enableConnectProtocol setting:
const http2 = require('http2');\nconst settings = { enableConnectProtocol: true };\nconst server = http2.createServer({ settings });\nOnce the client receives the SETTINGS frame from the server indicating that\nthe extended CONNECT may be used, it may send CONNECT requests that use the\n':protocol' HTTP/2 pseudo-header:
const http2 = require('http2');\nconst client = http2.connect('http://localhost:8080');\nclient.on('remoteSettings', (settings) => {\n if (settings.enableConnectProtocol) {\n const req = client.request({ ':method': 'CONNECT', ':protocol': 'foo' });\n // ...\n }\n});\nInstances of the http2.Http2Session class represent an active communications\nsession between an HTTP/2 client and server. Instances of this class are not\nintended to be constructed directly by user code.
Each Http2Session instance will exhibit slightly different behaviors\ndepending on whether it is operating as a server or a client. The\nhttp2session.type property can be used to determine the mode in which an\nHttp2Session is operating. On the server side, user code should rarely\nhave occasion to work with the Http2Session object directly, with most\nactions typically taken through interactions with either the Http2Server or\nHttp2Stream objects.
User code will not create Http2Session instances directly. Server-side\nHttp2Session instances are created by the Http2Server instance when a\nnew HTTP/2 connection is received. Client-side Http2Session instances are\ncreated using the http2.connect() method.
Every Http2Session instance is associated with exactly one net.Socket or\ntls.TLSSocket when it is created. When either the Socket or the\nHttp2Session are destroyed, both will be destroyed.
Because of the specific serialization and processing requirements imposed\nby the HTTP/2 protocol, it is not recommended for user code to read data from\nor write data to a Socket instance bound to a Http2Session. Doing so can\nput the HTTP/2 session into an indeterminate state causing the session and\nthe socket to become unusable.
Once a Socket has been bound to an Http2Session, user code should rely\nsolely on the API of the Http2Session.
The 'close' event is emitted once the Http2Session has been destroyed. Its\nlistener does not expect any arguments.
The 'connect' event is emitted once the Http2Session has been successfully\nconnected to the remote peer and communication may begin.
User code will typically not listen for this event directly.
" }, { "textRaw": "Event: 'error'", "type": "event", "name": "error", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [ { "textRaw": "`error` {Error}", "name": "error", "type": "Error" } ], "desc": "The 'error' event is emitted when an error occurs during the processing of\nan Http2Session.
The 'frameError' event is emitted when an error occurs while attempting to\nsend a frame on the session. If the frame that could not be sent is associated\nwith a specific Http2Stream, an attempt to emit 'frameError' event on the\nHttp2Stream is made.
If the 'frameError' event is associated with a stream, the stream will be\nclosed and destroyed immediately following the 'frameError' event. If the\nevent is not associated with a stream, the Http2Session will be shut down\nimmediately following the 'frameError' event.
The 'goaway' event is emitted when a GOAWAY frame is received.
The Http2Session instance will be shut down automatically when the 'goaway'\nevent is emitted.
The 'localSettings' event is emitted when an acknowledgment SETTINGS frame\nhas been received.
When using http2session.settings() to submit new settings, the modified\nsettings do not take effect until the 'localSettings' event is emitted.
session.settings({ enablePush: false });\n\nsession.on('localSettings', (settings) => {\n /* Use the new settings */\n});\nThe 'ping' event is emitted whenever a PING frame is received from the\nconnected peer.
The 'remoteSettings' event is emitted when a new SETTINGS frame is received\nfrom the connected peer.
session.on('remoteSettings', (settings) => {\n /* Use the new settings */\n});\nThe 'stream' event is emitted when a new Http2Stream is created.
const http2 = require('http2');\nsession.on('stream', (stream, headers, flags) => {\n const method = headers[':method'];\n const path = headers[':path'];\n // ...\n stream.respond({\n ':status': 200,\n 'content-type': 'text/plain'\n });\n stream.write('hello ');\n stream.end('world');\n});\nOn the server side, user code will typically not listen for this event directly,\nand would instead register a handler for the 'stream' event emitted by the\nnet.Server or tls.Server instances returned by http2.createServer() and\nhttp2.createSecureServer(), respectively, as in the example below:
const http2 = require('http2');\n\n// Create an unencrypted HTTP/2 server\nconst server = http2.createServer();\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html',\n ':status': 200\n });\n stream.on('error', (error) => console.error(error));\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\nEven though HTTP/2 streams and network sockets are not in a 1:1 correspondence,\na network error will destroy each individual stream and must be handled on the\nstream level, as shown above.
" }, { "textRaw": "Event: 'timeout'", "type": "event", "name": "timeout", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "After the http2session.setTimeout() method is used to set the timeout period\nfor this Http2Session, the 'timeout' event is emitted if there is no\nactivity on the Http2Session after the configured number of milliseconds.
session.setTimeout(2000);\nsession.on('timeout', () => { /* .. */ });\nValue will be undefined if the Http2Session is not yet connected to a\nsocket, h2c if the Http2Session is not connected to a TLSSocket, or\nwill return the value of the connected TLSSocket's own alpnProtocol\nproperty.
Will be true if this Http2Session instance has been closed, otherwise\nfalse.
Will be true if this Http2Session instance is still connecting, will be set\nto false before emitting connect event and/or calling the http2.connect\ncallback.
Will be true if this Http2Session instance has been destroyed and must no\nlonger be used, otherwise false.
Value is undefined if the Http2Session session socket has not yet been\nconnected, true if the Http2Session is connected with a TLSSocket,\nand false if the Http2Session is connected to any other kind of socket\nor stream.
A prototype-less object describing the current local settings of this\nHttp2Session. The local settings are local to this Http2Session instance.
If the Http2Session is connected to a TLSSocket, the originSet property\nwill return an Array of origins for which the Http2Session may be\nconsidered authoritative.
The originSet property is only available when using a secure TLS connection.
Indicates whether or not the Http2Session is currently waiting for an\nacknowledgment for a sent SETTINGS frame. Will be true after calling the\nhttp2session.settings() method. Will be false once all sent SETTINGS\nframes have been acknowledged.
A prototype-less object describing the current remote settings of this\nHttp2Session. The remote settings are set by the connected HTTP/2 peer.
Returns a Proxy object that acts as a net.Socket (or tls.TLSSocket) but\nlimits available methods to ones safe to use with HTTP/2.
destroy, emit, end, pause, read, resume, and write will throw\nan error with code ERR_HTTP2_NO_SOCKET_MANIPULATION. See\nHttp2Session and Sockets for more information.
setTimeout method will be called on this Http2Session.
All other interactions will be routed directly to the socket.
" }, { "textRaw": "http2session.state", "name": "state", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Provides miscellaneous information about the current state of the\nHttp2Session.
effectiveLocalWindowSize <number> The current local (receive)\nflow control window size for the Http2Session.effectiveRecvDataLength <number> The current number of bytes\nthat have been received since the last flow control WINDOW_UPDATE.nextStreamID <number> The numeric identifier to be used the\nnext time a new Http2Stream is created by this Http2Session.localWindowSize <number> The number of bytes that the remote peer can\nsend without receiving a WINDOW_UPDATE.lastProcStreamID <number> The numeric id of the Http2Stream\nfor which a HEADERS or DATA frame was most recently received.remoteWindowSize <number> The number of bytes that this Http2Session\nmay send without receiving a WINDOW_UPDATE.outboundQueueSize <number> The number of frames currently within the\noutbound queue for this Http2Session.deflateDynamicTableSize <number> The current size in bytes of the\noutbound header compression state table.inflateDynamicTableSize <number> The current size in bytes of the\ninbound header compression state table.An object describing the current status of this Http2Session.
The http2session.type will be equal to\nhttp2.constants.NGHTTP2_SESSION_SERVER if this Http2Session instance is a\nserver, and http2.constants.NGHTTP2_SESSION_CLIENT if the instance is a\nclient.
Gracefully closes the Http2Session, allowing any existing streams to\ncomplete on their own and preventing new Http2Stream instances from being\ncreated. Once closed, http2session.destroy() might be called if there\nare no open Http2Stream instances.
If specified, the callback function is registered as a handler for the\n'close' event.
Immediately terminates the Http2Session and the associated net.Socket or\ntls.TLSSocket.
Once destroyed, the Http2Session will emit the 'close' event. If error\nis not undefined, an 'error' event will be emitted immediately before the\n'close' event.
If there are any remaining open Http2Streams associated with the\nHttp2Session, those will also be destroyed.
Transmits a GOAWAY frame to the connected peer without shutting down the\nHttp2Session.
Sends a PING frame to the connected HTTP/2 peer. A callback function must\nbe provided. The method will return true if the PING was sent, false\notherwise.
The maximum number of outstanding (unacknowledged) pings is determined by the\nmaxOutstandingPings configuration option. The default maximum is 10.
If provided, the payload must be a Buffer, TypedArray, or DataView\ncontaining 8 bytes of data that will be transmitted with the PING and\nreturned with the ping acknowledgment.
The callback will be invoked with three arguments: an error argument that will\nbe null if the PING was successfully acknowledged, a duration argument\nthat reports the number of milliseconds elapsed since the ping was sent and the\nacknowledgment was received, and a Buffer containing the 8-byte PING\npayload.
session.ping(Buffer.from('abcdefgh'), (err, duration, payload) => {\n if (!err) {\n console.log(`Ping acknowledged in ${duration} milliseconds`);\n console.log(`With payload '${payload.toString()}'`);\n }\n});\nIf the payload argument is not specified, the default payload will be the\n64-bit timestamp (little endian) marking the start of the PING duration.
Calls ref() on this Http2Session\ninstance's underlying net.Socket.
Used to set a callback function that is called when there is no activity on\nthe Http2Session after msecs milliseconds. The given callback is\nregistered as a listener on the 'timeout' event.
Updates the current local settings for this Http2Session and sends a new\nSETTINGS frame to the connected HTTP/2 peer.
Once called, the http2session.pendingSettingsAck property will be true\nwhile the session is waiting for the remote peer to acknowledge the new\nsettings.
The new settings will not become effective until the SETTINGS acknowledgment\nis received and the 'localSettings' event is emitted. It is possible to send\nmultiple SETTINGS frames while acknowledgment is still pending.
Calls unref() on this Http2Session\ninstance's underlying net.Socket.
Submits an ALTSVC frame (as defined by RFC 7838) to the connected client.
const http2 = require('http2');\n\nconst server = http2.createServer();\nserver.on('session', (session) => {\n // Set altsvc for origin https://example.org:80\n session.altsvc('h2=\":8000\"', 'https://example.org:80');\n});\n\nserver.on('stream', (stream) => {\n // Set altsvc for a specific stream\n stream.session.altsvc('h2=\":8000\"', stream.id);\n});\nSending an ALTSVC frame with a specific stream ID indicates that the alternate\nservice is associated with the origin of the given Http2Stream.
The alt and origin string must contain only ASCII bytes and are\nstrictly interpreted as a sequence of ASCII bytes. The special value 'clear'\nmay be passed to clear any previously set alternative service for a given\ndomain.
When a string is passed for the originOrStream argument, it will be parsed as\na URL and the origin will be derived. For instance, the origin for the\nHTTP URL 'https://example.org/foo/bar' is the ASCII string\n'https://example.org'. An error will be thrown if either the given string\ncannot be parsed as a URL or if a valid origin cannot be derived.
A URL object, or any object with an origin property, may be passed as\noriginOrStream, in which case the value of the origin property will be\nused. The value of the origin property must be a properly serialized\nASCII origin.
Submits an ORIGIN frame (as defined by RFC 8336) to the connected client\nto advertise the set of origins for which the server is capable of providing\nauthoritative responses.
const http2 = require('http2');\nconst options = getSecureOptionsSomehow();\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream) => {\n stream.respond();\n stream.end('ok');\n});\nserver.on('session', (session) => {\n session.origin('https://example.com', 'https://example.org');\n});\nWhen a string is passed as an origin, it will be parsed as a URL and the\norigin will be derived. For instance, the origin for the HTTP URL\n'https://example.org/foo/bar' is the ASCII string\n'https://example.org'. An error will be thrown if either the given string\ncannot be parsed as a URL or if a valid origin cannot be derived.
A URL object, or any object with an origin property, may be passed as\nan origin, in which case the value of the origin property will be\nused. The value of the origin property must be a properly serialized\nASCII origin.
Alternatively, the origins option may be used when creating a new HTTP/2\nserver using the http2.createSecureServer() method:
const http2 = require('http2');\nconst options = getSecureOptionsSomehow();\noptions.origins = ['https://example.com', 'https://example.org'];\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream) => {\n stream.respond();\n stream.end('ok');\n});\nThe format of the alt parameter is strictly defined by RFC 7838 as an\nASCII string containing a comma-delimited list of \"alternative\" protocols\nassociated with a specific host and port.
For example, the value 'h2=\"example.org:81\"' indicates that the HTTP/2\nprotocol is available on the host 'example.org' on TCP/IP port 81. The\nhost and port must be contained within the quote (\") characters.
Multiple alternatives may be specified, for instance: 'h2=\"example.org:81\", h2=\":82\"'.
The protocol identifier ('h2' in the examples) may be any valid\nALPN Protocol ID.
The syntax of these values is not validated by the Node.js implementation and\nare passed through as provided by the user or received from the peer.
", "type": "module", "displayName": "Specifying alternative services" } ] }, { "textRaw": "Class: ClientHttp2Session", "type": "class", "name": "ClientHttp2Session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "events": [ { "textRaw": "Event: 'altsvc'", "type": "event", "name": "altsvc", "meta": { "added": [ "v9.4.0" ], "changes": [] }, "params": [ { "textRaw": "`alt` {string}", "name": "alt", "type": "string" }, { "textRaw": "`origin` {string}", "name": "origin", "type": "string" }, { "textRaw": "`streamId` {number}", "name": "streamId", "type": "number" } ], "desc": "The 'altsvc' event is emitted whenever an ALTSVC frame is received by\nthe client. The event is emitted with the ALTSVC value, origin, and stream\nID. If no origin is provided in the ALTSVC frame, origin will\nbe an empty string.
const http2 = require('http2');\nconst client = http2.connect('https://example.org');\n\nclient.on('altsvc', (alt, origin, streamId) => {\n console.log(alt);\n console.log(origin);\n console.log(streamId);\n});\nThe 'origin' event is emitted whenever an ORIGIN frame is received by\nthe client. The event is emitted with an array of origin strings. The\nhttp2session.originSet will be updated to include the received\norigins.
const http2 = require('http2');\nconst client = http2.connect('https://example.org');\n\nclient.on('origin', (origins) => {\n for (let n = 0; n < origins.length; n++)\n console.log(origins[n]);\n});\nThe 'origin' event is only emitted when using a secure TLS connection.
For HTTP/2 Client Http2Session instances only, the http2session.request()\ncreates and returns an Http2Stream instance that can be used to send an\nHTTP/2 request to the connected server.
This method is only available if http2session.type is equal to\nhttp2.constants.NGHTTP2_SESSION_CLIENT.
const http2 = require('http2');\nconst clientSession = http2.connect('https://localhost:1234');\nconst {\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS\n} = http2.constants;\n\nconst req = clientSession.request({ [HTTP2_HEADER_PATH]: '/' });\nreq.on('response', (headers) => {\n console.log(headers[HTTP2_HEADER_STATUS]);\n req.on('data', (chunk) => { /* .. */ });\n req.on('end', () => { /* .. */ });\n});\nWhen the options.waitForTrailers option is set, the 'wantTrailers' event\nis emitted immediately after queuing the last chunk of payload data to be sent.\nThe http2stream.sendTrailers() method can then be called to send trailing\nheaders to the peer.
When options.waitForTrailers is set, the Http2Stream will not automatically\nclose when the final DATA frame is transmitted. User code must call either\nhttp2stream.sendTrailers() or http2stream.close() to close the\nHttp2Stream.
The :method and :path pseudo-headers are not specified within headers,\nthey respectively default to:
:method = 'GET':path = /Each instance of the Http2Stream class represents a bidirectional HTTP/2\ncommunications stream over an Http2Session instance. Any single Http2Session\nmay have up to 231-1 Http2Stream instances over its lifetime.
User code will not construct Http2Stream instances directly. Rather, these\nare created, managed, and provided to user code through the Http2Session\ninstance. On the server, Http2Stream instances are created either in response\nto an incoming HTTP request (and handed off to user code via the 'stream'\nevent), or in response to a call to the http2stream.pushStream() method.\nOn the client, Http2Stream instances are created and returned when either the\nhttp2session.request() method is called, or in response to an incoming\n'push' event.
The Http2Stream class is a base for the ServerHttp2Stream and\nClientHttp2Stream classes, each of which is used specifically by either\nthe Server or Client side, respectively.
All Http2Stream instances are Duplex streams. The Writable side of the\nDuplex is used to send data to the connected peer, while the Readable side\nis used to receive data sent by the connected peer.
On the server side, instances of ServerHttp2Stream are created either\nwhen:
HEADERS frame with a previously unused stream ID is received;http2stream.pushStream() method is called.On the client side, instances of ClientHttp2Stream are created when the\nhttp2session.request() method is called.
On the client, the Http2Stream instance returned by http2session.request()\nmay not be immediately ready for use if the parent Http2Session has not yet\nbeen fully established. In such cases, operations called on the Http2Stream\nwill be buffered until the 'ready' event is emitted. User code should rarely,\nif ever, need to handle the 'ready' event directly. The ready status of an\nHttp2Stream can be determined by checking the value of http2stream.id. If\nthe value is undefined, the stream is not yet ready for use.
All Http2Stream instances are destroyed either when:
RST_STREAM frame for the stream is received by the connected peer,\nand pending data has been read.http2stream.close() method is called, and pending data has been read.http2stream.destroy() or http2session.destroy() methods are called.When an Http2Stream instance is destroyed, an attempt will be made to send an\nRST_STREAM frame will be sent to the connected peer.
When the Http2Stream instance is destroyed, the 'close' event will\nbe emitted. Because Http2Stream is an instance of stream.Duplex, the\n'end' event will also be emitted if the stream data is currently flowing.\nThe 'error' event may also be emitted if http2stream.destroy() was called\nwith an Error passed as the first argument.
After the Http2Stream has been destroyed, the http2stream.destroyed\nproperty will be true and the http2stream.rstCode property will specify the\nRST_STREAM error code. The Http2Stream instance is no longer usable once\ndestroyed.
The 'aborted' event is emitted whenever a Http2Stream instance is\nabnormally aborted in mid-communication.
The 'aborted' event will only be emitted if the Http2Stream writable side\nhas not been ended.
The 'close' event is emitted when the Http2Stream is destroyed. Once\nthis event is emitted, the Http2Stream instance is no longer usable.
The HTTP/2 error code used when closing the stream can be retrieved using\nthe http2stream.rstCode property. If the code is any value other than\nNGHTTP2_NO_ERROR (0), an 'error' event will have also been emitted.
The 'error' event is emitted when an error occurs during the processing of\nan Http2Stream.
The 'frameError' event is emitted when an error occurs while attempting to\nsend a frame. When invoked, the handler function will receive an integer\nargument identifying the frame type, and an integer argument identifying the\nerror code. The Http2Stream instance will be destroyed immediately after the\n'frameError' event is emitted.
The 'timeout' event is emitted after no activity is received for this\nHttp2Stream within the number of milliseconds set using\nhttp2stream.setTimeout().
The 'trailers' event is emitted when a block of headers associated with\ntrailing header fields is received. The listener callback is passed the\nHTTP/2 Headers Object and flags associated with the headers.
Note that this event might not be emitted if http2stream.end() is called\nbefore trailers are received and the incoming data is not being read or\nlistened for.
stream.on('trailers', (headers, flags) => {\n console.log(headers);\n});\nThe 'wantTrailers' event is emitted when the Http2Stream has queued the\nfinal DATA frame to be sent on a frame and the Http2Stream is ready to send\ntrailing headers. When initiating a request or response, the waitForTrailers\noption must be set for this event to be emitted.
Set to true if the Http2Stream instance was aborted abnormally. When set,\nthe 'aborted' event will have been emitted.
This property shows the number of characters currently buffered to be written.\nSee net.Socket.bufferSize for details.
Set to true if the Http2Stream instance has been closed.
Set to true if the Http2Stream instance has been destroyed and is no longer\nusable.
Set the true if the END_STREAM flag was set in the request or response\nHEADERS frame received, indicating that no additional data should be received\nand the readable side of the Http2Stream will be closed.
Set to true if the Http2Stream instance has not yet been assigned a\nnumeric stream identifier.
Set to the RST_STREAM error code reported when the Http2Stream is\ndestroyed after either receiving an RST_STREAM frame from the connected peer,\ncalling http2stream.close(), or http2stream.destroy(). Will be\nundefined if the Http2Stream has not been closed.
An object containing the outbound headers sent for this Http2Stream.
An array of objects containing the outbound informational (additional) headers\nsent for this Http2Stream.
An object containing the outbound trailers sent for this HttpStream.
A reference to the Http2Session instance that owns this Http2Stream. The\nvalue will be undefined after the Http2Stream instance is destroyed.
Provides miscellaneous information about the current state of the\nHttp2Stream.
localWindowSize <number> The number of bytes the connected peer may send\nfor this Http2Stream without receiving a WINDOW_UPDATE.state <number> A flag indicating the low-level current state of the\nHttp2Stream as determined by nghttp2.localClose <number> true if this Http2Stream has been closed locally.remoteClose <number> true if this Http2Stream has been closed\nremotely.sumDependencyWeight <number> The sum weight of all Http2Stream\ninstances that depend on this Http2Stream as specified using\nPRIORITY frames.weight <number> The priority weight of this Http2Stream.A current state of this Http2Stream.
Closes the Http2Stream instance by sending an RST_STREAM frame to the\nconnected HTTP/2 peer.
Updates the priority for this Http2Stream instance.
const http2 = require('http2');\nconst client = http2.connect('http://example.org:8000');\nconst { NGHTTP2_CANCEL } = http2.constants;\nconst req = client.request({ ':path': '/' });\n\n// Cancel the stream if there's no activity after 5 seconds\nreq.setTimeout(5000, () => req.close(NGHTTP2_CANCEL));\nSends a trailing HEADERS frame to the connected HTTP/2 peer. This method\nwill cause the Http2Stream to be immediately closed and must only be\ncalled after the 'wantTrailers' event has been emitted. When sending a\nrequest or sending a response, the options.waitForTrailers option must be set\nin order to keep the Http2Stream open after the final DATA frame so that\ntrailers can be sent.
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond(undefined, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ xyz: 'abc' });\n });\n stream.end('Hello World');\n});\nThe HTTP/1 specification forbids trailers from containing HTTP/2 pseudo-header\nfields (e.g. ':method', ':path', etc).
The ClientHttp2Stream class is an extension of Http2Stream that is\nused exclusively on HTTP/2 Clients. Http2Stream instances on the client\nprovide events such as 'response' and 'push' that are only relevant on\nthe client.
Emitted when the server sends a 100 Continue status, usually because\nthe request contained Expect: 100-continue. This is an instruction that\nthe client should send the request body.
The 'headers' event is emitted when an additional block of headers is received\nfor a stream, such as when a block of 1xx informational headers is received.\nThe listener callback is passed the HTTP/2 Headers Object and flags\nassociated with the headers.
stream.on('headers', (headers, flags) => {\n console.log(headers);\n});\nThe 'push' event is emitted when response headers for a Server Push stream\nare received. The listener callback is passed the HTTP/2 Headers Object and\nflags associated with the headers.
stream.on('push', (headers, flags) => {\n console.log(headers);\n});\nThe 'response' event is emitted when a response HEADERS frame has been\nreceived for this stream from the connected HTTP/2 server. The listener is\ninvoked with two arguments: an Object containing the received\nHTTP/2 Headers Object, and flags associated with the headers.
const http2 = require('http2');\nconst client = http2.connect('https://localhost');\nconst req = client.request({ ':path': '/' });\nreq.on('response', (headers, flags) => {\n console.log(headers[':status']);\n});\nThe ServerHttp2Stream class is an extension of Http2Stream that is\nused exclusively on HTTP/2 Servers. Http2Stream instances on the server\nprovide additional methods such as http2stream.pushStream() and\nhttp2stream.respond() that are only relevant on the server.
Sends an additional informational HEADERS frame to the connected HTTP/2 peer.
Initiates a push stream. The callback is invoked with the new Http2Stream\ninstance created for the push stream passed as the second argument, or an\nError passed as the first argument.
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 });\n stream.pushStream({ ':path': '/' }, (err, pushStream, headers) => {\n if (err) throw err;\n pushStream.respond({ ':status': 200 });\n pushStream.end('some pushed data');\n });\n stream.end('some data');\n});\nSetting the weight of a push stream is not allowed in the HEADERS frame. Pass\na weight value to http2stream.priority with the silent option set to\ntrue to enable server-side bandwidth balancing between concurrent streams.
Calling http2stream.pushStream() from within a pushed stream is not permitted\nand will throw an error.
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 });\n stream.end('some data');\n});\nWhen the options.waitForTrailers option is set, the 'wantTrailers' event\nwill be emitted immediately after queuing the last chunk of payload data to be\nsent. The http2stream.sendTrailers() method can then be used to sent trailing\nheader fields to the peer.
When options.waitForTrailers is set, the Http2Stream will not automatically\nclose when the final DATA frame is transmitted. User code must call either\nhttp2stream.sendTrailers() or http2stream.close() to close the\nHttp2Stream.
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respond({ ':status': 200 }, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n stream.end('some data');\n});\nInitiates a response whose data is read from the given file descriptor. No\nvalidation is performed on the given file descriptor. If an error occurs while\nattempting to read data using the file descriptor, the Http2Stream will be\nclosed using an RST_STREAM frame using the standard INTERNAL_ERROR code.
When used, the Http2Stream object's Duplex interface will be closed\nautomatically.
const http2 = require('http2');\nconst fs = require('fs');\n\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n const fd = fs.openSync('/some/file', 'r');\n\n const stat = fs.fstatSync(fd);\n const headers = {\n 'content-length': stat.size,\n 'last-modified': stat.mtime.toUTCString(),\n 'content-type': 'text/plain'\n };\n stream.respondWithFD(fd, headers);\n stream.on('close', () => fs.closeSync(fd));\n});\nThe optional options.statCheck function may be specified to give user code\nan opportunity to set additional content headers based on the fs.Stat details\nof the given fd. If the statCheck function is provided, the\nhttp2stream.respondWithFD() method will perform an fs.fstat() call to\ncollect details on the provided file descriptor.
The offset and length options may be used to limit the response to a\nspecific range subset. This can be used, for instance, to support HTTP Range\nrequests.
The file descriptor is not closed when the stream is closed, so it will need\nto be closed manually once it is no longer needed.\nNote that using the same file descriptor concurrently for multiple streams\nis not supported and may result in data loss. Re-using a file descriptor\nafter a stream has finished is supported.
\nWhen the options.waitForTrailers option is set, the 'wantTrailers' event\nwill be emitted immediately after queuing the last chunk of payload data to be\nsent. The http2stream.sendTrailers() method can then be used to sent trailing\nheader fields to the peer.
When options.waitForTrailers is set, the Http2Stream will not automatically\nclose when the final DATA frame is transmitted. User code must call either\nhttp2stream.sendTrailers() or http2stream.close() to close the\nHttp2Stream.
const http2 = require('http2');\nconst fs = require('fs');\n\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n const fd = fs.openSync('/some/file', 'r');\n\n const stat = fs.fstatSync(fd);\n const headers = {\n 'content-length': stat.size,\n 'last-modified': stat.mtime.toUTCString(),\n 'content-type': 'text/plain'\n };\n stream.respondWithFD(fd, headers, { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n\n stream.on('close', () => fs.closeSync(fd));\n});\nSends a regular file as the response. The path must specify a regular file\nor an 'error' event will be emitted on the Http2Stream object.
When used, the Http2Stream object's Duplex interface will be closed\nautomatically.
The optional options.statCheck function may be specified to give user code\nan opportunity to set additional content headers based on the fs.Stat details\nof the given file:
If an error occurs while attempting to read the file data, the Http2Stream\nwill be closed using an RST_STREAM frame using the standard INTERNAL_ERROR\ncode. If the onError callback is defined, then it will be called. Otherwise\nthe stream will be destroyed.
Example using a file path:
\nconst http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n function statCheck(stat, headers) {\n headers['last-modified'] = stat.mtime.toUTCString();\n }\n\n function onError(err) {\n if (err.code === 'ENOENT') {\n stream.respond({ ':status': 404 });\n } else {\n stream.respond({ ':status': 500 });\n }\n stream.end();\n }\n\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain' },\n { statCheck, onError });\n});\nThe options.statCheck function may also be used to cancel the send operation\nby returning false. For instance, a conditional request may check the stat\nresults to determine if the file has been modified to return an appropriate\n304 response:
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n function statCheck(stat, headers) {\n // Check the stat here...\n stream.respond({ ':status': 304 });\n return false; // Cancel the send operation\n }\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain' },\n { statCheck });\n});\nThe content-length header field will be automatically set.
The offset and length options may be used to limit the response to a\nspecific range subset. This can be used, for instance, to support HTTP Range\nrequests.
The options.onError function may also be used to handle all the errors\nthat could happen before the delivery of the file is initiated. The\ndefault behavior is to destroy the stream.
When the options.waitForTrailers option is set, the 'wantTrailers' event\nwill be emitted immediately after queuing the last chunk of payload data to be\nsent. The http2stream.sendTrailers() method can then be used to sent trailing\nheader fields to the peer.
When options.waitForTrailers is set, the Http2Stream will not automatically\nclose when the final DATA frame is transmitted. User code must call either\nhttp2stream.sendTrailers() or http2stream.close() to close the\nHttp2Stream.
const http2 = require('http2');\nconst server = http2.createServer();\nserver.on('stream', (stream) => {\n stream.respondWithFile('/some/file',\n { 'content-type': 'text/plain' },\n { waitForTrailers: true });\n stream.on('wantTrailers', () => {\n stream.sendTrailers({ ABC: 'some value to send' });\n });\n});\nTrue if headers were sent, false otherwise (read-only).
" }, { "textRaw": "`pushAllowed` {boolean}", "type": "boolean", "name": "pushAllowed", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Read-only property mapped to the SETTINGS_ENABLE_PUSH flag of the remote\nclient's most recent SETTINGS frame. Will be true if the remote peer\naccepts push streams, false otherwise. Settings are the same for every\nHttp2Stream in the same Http2Session.
Instances of Http2Server are created using the http2.createServer()\nfunction. The Http2Server class is not exported directly by the http2\nmodule.
If a 'request' listener is registered or http2.createServer() is\nsupplied a callback function, the 'checkContinue' event is emitted each time\na request with an HTTP Expect: 100-continue is received. If this event is\nnot listened for, the server will automatically respond with a status\n100 Continue as appropriate.
Handling this event involves calling response.writeContinue() if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
Note that when this event is emitted and handled, the 'request' event will\nnot be emitted.
Emitted each time there is a request. Note that there may be multiple requests\nper session. See the Compatibility API.
" }, { "textRaw": "Event: 'session'", "type": "event", "name": "session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "The 'session' event is emitted when a new Http2Session is created by the\nHttp2Server.
The 'sessionError' event is emitted when an 'error' event is emitted by\nan Http2Session object associated with the Http2Server.
The 'stream' event is emitted when a 'stream' event has been emitted by\nan Http2Session associated with the server.
const http2 = require('http2');\nconst {\n HTTP2_HEADER_METHOD,\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS,\n HTTP2_HEADER_CONTENT_TYPE\n} = http2.constants;\n\nconst server = http2.createServer();\nserver.on('stream', (stream, headers, flags) => {\n const method = headers[HTTP2_HEADER_METHOD];\n const path = headers[HTTP2_HEADER_PATH];\n // ...\n stream.respond({\n [HTTP2_HEADER_STATUS]: 200,\n [HTTP2_HEADER_CONTENT_TYPE]: 'text/plain'\n });\n stream.write('hello ');\n stream.end('world');\n});\nThe 'timeout' event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2server.setTimeout().\nDefault: 2 minutes.
Stops the server from accepting new connections. See net.Server.close().
Note that this is not analogous to restricting new requests since HTTP/2\nconnections are persistent. To achieve a similar graceful shutdown behavior,\nconsider also using http2session.close() on active sessions.
Used to set the timeout value for http2 server requests,\nand sets a callback function that is called when there is no activity\non the Http2Server after msecs milliseconds.
The given callback is registered as a listener on the 'timeout' event.
In case of no callback function were assigned, a new ERR_INVALID_CALLBACK\nerror will be thrown.
Instances of Http2SecureServer are created using the\nhttp2.createSecureServer() function. The Http2SecureServer class is not\nexported directly by the http2 module.
If a 'request' listener is registered or http2.createSecureServer()\nis supplied a callback function, the 'checkContinue' event is emitted each\ntime a request with an HTTP Expect: 100-continue is received. If this event\nis not listened for, the server will automatically respond with a status\n100 Continue as appropriate.
Handling this event involves calling response.writeContinue() if the\nclient should continue to send the request body, or generating an appropriate\nHTTP response (e.g. 400 Bad Request) if the client should not continue to send\nthe request body.
Note that when this event is emitted and handled, the 'request' event will\nnot be emitted.
Emitted each time there is a request. Note that there may be multiple requests\nper session. See the Compatibility API.
" }, { "textRaw": "Event: 'session'", "type": "event", "name": "session", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "The 'session' event is emitted when a new Http2Session is created by the\nHttp2SecureServer.
The 'sessionError' event is emitted when an 'error' event is emitted by\nan Http2Session object associated with the Http2SecureServer.
The 'stream' event is emitted when a 'stream' event has been emitted by\nan Http2Session associated with the server.
const http2 = require('http2');\nconst {\n HTTP2_HEADER_METHOD,\n HTTP2_HEADER_PATH,\n HTTP2_HEADER_STATUS,\n HTTP2_HEADER_CONTENT_TYPE\n} = http2.constants;\n\nconst options = getOptionsSomehow();\n\nconst server = http2.createSecureServer(options);\nserver.on('stream', (stream, headers, flags) => {\n const method = headers[HTTP2_HEADER_METHOD];\n const path = headers[HTTP2_HEADER_PATH];\n // ...\n stream.respond({\n [HTTP2_HEADER_STATUS]: 200,\n [HTTP2_HEADER_CONTENT_TYPE]: 'text/plain'\n });\n stream.write('hello ');\n stream.end('world');\n});\nThe 'timeout' event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2secureServer.setTimeout().\nDefault: 2 minutes.
The 'unknownProtocol' event is emitted when a connecting client fails to\nnegotiate an allowed protocol (i.e. HTTP/2 or HTTP/1.1). The event handler\nreceives the socket for handling. If no listener is registered for this event,\nthe connection is terminated. See the Compatibility API.
Stops the server from accepting new connections. See tls.Server.close().
Note that this is not analogous to restricting new requests since HTTP/2\nconnections are persistent. To achieve a similar graceful shutdown behavior,\nconsider also using http2session.close() on active sessions.
Used to set the timeout value for http2 secure server requests,\nand sets a callback function that is called when there is no activity\non the Http2SecureServer after msecs milliseconds.
The given callback is registered as a listener on the 'timeout' event.
In case of no callback function were assigned, a new ERR_INVALID_CALLBACK\nerror will be thrown.
Returns a net.Server instance that creates and manages Http2Session\ninstances.
Since there are no browsers known that support\nunencrypted HTTP/2, the use of\nhttp2.createSecureServer() is necessary when communicating\nwith browser clients.
const http2 = require('http2');\n\n// Create an unencrypted HTTP/2 server.\n// Since there are no browsers known that support\n// unencrypted HTTP/2, the use of `http2.createSecureServer()`\n// is necessary when communicating with browser clients.\nconst server = http2.createServer();\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html',\n ':status': 200\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\nReturns a tls.Server instance that creates and manages Http2Session\ninstances.
const http2 = require('http2');\nconst fs = require('fs');\n\nconst options = {\n key: fs.readFileSync('server-key.pem'),\n cert: fs.readFileSync('server-cert.pem')\n};\n\n// Create a secure HTTP/2 server\nconst server = http2.createSecureServer(options);\n\nserver.on('stream', (stream, headers) => {\n stream.respond({\n 'content-type': 'text/html',\n ':status': 200\n });\n stream.end('<h1>Hello World</h1>');\n});\n\nserver.listen(80);\nReturns a ClientHttp2Session instance.
const http2 = require('http2');\nconst client = http2.connect('https://localhost:1234');\n\n/* Use the client */\n\nclient.close();\nReturns an object containing the default settings for an Http2Session\ninstance. This method returns a new object instance every time it is called\nso instances returned may be safely modified for use.
Returns a Buffer instance containing serialized representation of the given\nHTTP/2 settings as specified in the HTTP/2 specification. This is intended\nfor use with the HTTP2-Settings header field.
const http2 = require('http2');\n\nconst packed = http2.getPackedSettings({ enablePush: false });\n\nconsole.log(packed.toString('base64'));\n// Prints: AAIAAAAA\nReturns a HTTP/2 Settings Object containing the deserialized settings from\nthe given Buffer as generated by http2.getPackedSettings().
| Value | \nName | \nConstant | \n
|---|---|---|
0x00 | \nNo Error | \nhttp2.constants.NGHTTP2_NO_ERROR | \n
0x01 | \nProtocol Error | \nhttp2.constants.NGHTTP2_PROTOCOL_ERROR | \n
0x02 | \nInternal Error | \nhttp2.constants.NGHTTP2_INTERNAL_ERROR | \n
0x03 | \nFlow Control Error | \nhttp2.constants.NGHTTP2_FLOW_CONTROL_ERROR | \n
0x04 | \nSettings Timeout | \nhttp2.constants.NGHTTP2_SETTINGS_TIMEOUT | \n
0x05 | \nStream Closed | \nhttp2.constants.NGHTTP2_STREAM_CLOSED | \n
0x06 | \nFrame Size Error | \nhttp2.constants.NGHTTP2_FRAME_SIZE_ERROR | \n
0x07 | \nRefused Stream | \nhttp2.constants.NGHTTP2_REFUSED_STREAM | \n
0x08 | \nCancel | \nhttp2.constants.NGHTTP2_CANCEL | \n
0x09 | \nCompression Error | \nhttp2.constants.NGHTTP2_COMPRESSION_ERROR | \n
0x0a | \nConnect Error | \nhttp2.constants.NGHTTP2_CONNECT_ERROR | \n
0x0b | \nEnhance Your Calm | \nhttp2.constants.NGHTTP2_ENHANCE_YOUR_CALM | \n
0x0c | \nInadequate Security | \nhttp2.constants.NGHTTP2_INADEQUATE_SECURITY | \n
0x0d | \nHTTP/1.1 Required | \nhttp2.constants.NGHTTP2_HTTP_1_1_REQUIRED | \n
The 'timeout' event is emitted when there is no activity on the Server for\na given number of milliseconds set using http2server.setTimeout().
The Compatibility API has the goal of providing a similar developer experience\nof HTTP/1 when using HTTP/2, making it possible to develop applications\nthat support both HTTP/1 and HTTP/2. This API targets only the\npublic API of the HTTP/1. However many modules use internal\nmethods or state, and those are not supported as it is a completely\ndifferent implementation.
\nThe following example creates an HTTP/2 server using the compatibility\nAPI:
\nconst http2 = require('http2');\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\nIn order to create a mixed HTTPS and HTTP/2 server, refer to the\nALPN negotiation section.\nUpgrading from non-tls HTTP/1 servers is not supported.
\nThe HTTP/2 compatibility API is composed of Http2ServerRequest and\nHttp2ServerResponse. They aim at API compatibility with HTTP/1, but\nthey do not hide the differences between the protocols. As an example,\nthe status message for HTTP codes is ignored.
ALPN negotiation allows supporting both HTTPS and HTTP/2 over\nthe same socket. The req and res objects can be either HTTP/1 or\nHTTP/2, and an application must restrict itself to the public API of\nHTTP/1, and detect if it is possible to use the more advanced\nfeatures of HTTP/2.
The following example creates a server that supports both protocols:
\nconst { createSecureServer } = require('http2');\nconst { readFileSync } = require('fs');\n\nconst cert = readFileSync('./cert.pem');\nconst key = readFileSync('./key.pem');\n\nconst server = createSecureServer(\n { cert, key, allowHTTP1: true },\n onRequest\n).listen(4443);\n\nfunction onRequest(req, res) {\n // detects if it is a HTTPS request or HTTP/2\n const { socket: { alpnProtocol } } = req.httpVersion === '2.0' ?\n req.stream.session : req;\n res.writeHead(200, { 'content-type': 'application/json' });\n res.end(JSON.stringify({\n alpnProtocol,\n httpVersion: req.httpVersion\n }));\n}\nThe 'request' event works identically on both HTTPS and\nHTTP/2.
A Http2ServerRequest object is created by http2.Server or\nhttp2.SecureServer and passed as the first argument to the\n'request' event. It may be used to access a request status, headers, and\ndata.
It implements the Readable Stream interface, as well as the\nfollowing additional events, methods, and properties.
", "events": [ { "textRaw": "Event: 'aborted'", "type": "event", "name": "aborted", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "The 'aborted' event is emitted whenever a Http2ServerRequest instance is\nabnormally aborted in mid-communication.
The 'aborted' event will only be emitted if the Http2ServerRequest writable\nside has not been ended.
Indicates that the underlying Http2Stream was closed.\nJust like 'end', this event occurs only once per response.
The request.aborted property will be true if the request has\nbeen aborted.
The request authority pseudo header field. It can also be accessed via\nreq.headers[':authority'].
The request/response headers object.
\nKey-value pairs of header names and values. Header names are lower-cased.
\n// Prints something like:\n//\n// { 'user-agent': 'curl/7.22.0',\n// host: '127.0.0.1:8000',\n// accept: '*/*' }\nconsole.log(request.headers);\nIn HTTP/2, the request path, hostname, protocol, and method are represented as\nspecial headers prefixed with the : character (e.g. ':path'). These special\nheaders will be included in the request.headers object. Care must be taken not\nto inadvertently modify these special headers or errors may occur. For instance,\nremoving all headers from the request will cause errors to occur:
removeAllHeaders(request.headers);\nassert(request.url); // Fails because the :path header has been removed\nIn case of server request, the HTTP version sent by the client. In the case of\nclient response, the HTTP version of the connected-to server. Returns\n'2.0'.
Also message.httpVersionMajor is the first integer and\nmessage.httpVersionMinor is the second.
The request method as a string. Read-only. Examples: 'GET', 'DELETE'.
The raw request/response headers list exactly as they were received.
\nNote that the keys and values are in the same list. It is not a\nlist of tuples. So, the even-numbered offsets are key values, and the\nodd-numbered offsets are the associated values.
\nHeader names are not lowercased, and duplicates are not merged.
\n// Prints something like:\n//\n// [ 'user-agent',\n// 'this is invalid because there can be only one',\n// 'User-Agent',\n// 'curl/7.22.0',\n// 'Host',\n// '127.0.0.1:8000',\n// 'ACCEPT',\n// '*/*' ]\nconsole.log(request.rawHeaders);\nThe raw request/response trailer keys and values exactly as they were\nreceived. Only populated at the 'end' event.
The request scheme pseudo header field indicating the scheme\nportion of the target URL.
" }, { "textRaw": "`socket` {net.Socket|tls.TLSSocket}", "type": "net.Socket|tls.TLSSocket", "name": "socket", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Returns a Proxy object that acts as a net.Socket (or tls.TLSSocket) but\napplies getters, setters, and methods based on HTTP/2 logic.
destroyed, readable, and writable properties will be retrieved from and\nset on request.stream.
destroy, emit, end, on and once methods will be called on\nrequest.stream.
setTimeout method will be called on request.stream.session.
pause, read, resume, and write will throw an error with code\nERR_HTTP2_NO_SOCKET_MANIPULATION. See Http2Session and Sockets for\nmore information.
All other interactions will be routed directly to the socket. With TLS support,\nuse request.socket.getPeerCertificate() to obtain the client's\nauthentication details.
The Http2Stream object backing the request.
The request/response trailers object. Only populated at the 'end' event.
Request URL string. This contains only the URL that is\npresent in the actual HTTP request. If the request is:
\nGET /status?name=ryan HTTP/1.1\\r\\n\nAccept: text/plain\\r\\n\n\\r\\n\nThen request.url will be:
'/status?name=ryan'\nTo parse the url into its parts require('url').parse(request.url)\ncan be used:
$ node\n> require('url').parse('/status?name=ryan')\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: 'name=ryan',\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\nTo extract the parameters from the query string, the\nrequire('querystring').parse function can be used, or\ntrue can be passed as the second argument to require('url').parse.
$ node\n> require('url').parse('/status?name=ryan', true)\nUrl {\n protocol: null,\n slashes: null,\n auth: null,\n host: null,\n port: null,\n hostname: null,\n hash: null,\n search: '?name=ryan',\n query: { name: 'ryan' },\n pathname: '/status',\n path: '/status?name=ryan',\n href: '/status?name=ryan' }\nCalls destroy() on the Http2Stream that received\nthe Http2ServerRequest. If error is provided, an 'error' event\nis emitted and error is passed as an argument to any listeners on the event.
It does nothing if the stream was already destroyed.
" }, { "textRaw": "request.setTimeout(msecs, callback)", "type": "method", "name": "setTimeout", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {http2.Http2ServerRequest}", "name": "return", "type": "http2.Http2ServerRequest" }, "params": [ { "textRaw": "`msecs` {number}", "name": "msecs", "type": "number" }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Sets the Http2Stream's timeout value to msecs. If a callback is\nprovided, then it is added as a listener on the 'timeout' event on\nthe response object.
If no 'timeout' listener is added to the request, the response, or\nthe server, then Http2Streams are destroyed when they time out. If a\nhandler is assigned to the request, the response, or the server's 'timeout'\nevents, timed out sockets must be handled explicitly.
This object is created internally by an HTTP server — not by the user. It is\npassed as the second parameter to the 'request' event.
The response inherits from Stream, and additionally implements the\nfollowing:
", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "params": [], "desc": "Indicates that the underlying Http2Stream was terminated before\nresponse.end() was called or able to flush.
Emitted when the response has been sent. More specifically, this event is\nemitted when the last segment of the response headers and body have been\nhanded off to the HTTP/2 multiplexing for transmission over the network. It\ndoes not imply that the client has received anything yet.
\nAfter this event, no more events will be emitted on the response object.
" } ], "methods": [ { "textRaw": "response.addTrailers(headers)", "type": "method", "name": "addTrailers", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`headers` {Object}", "name": "headers", "type": "Object" } ] } ], "desc": "This method adds HTTP trailing headers (a header but at the end of the\nmessage) to the response.
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
This method signals to the server that all of the response headers and body\nhave been sent; that server should consider this message complete.\nThe method, response.end(), MUST be called on each response.
If data is specified, it is equivalent to calling\nresponse.write(data, encoding) followed by response.end(callback).
If callback is specified, it will be called when the response stream\nis finished.
Reads out a header that has already been queued but not sent to the client.\nNote that the name is case insensitive.
\nconst contentType = response.getHeader('content-type');\nReturns an array containing the unique names of the current outgoing headers.\nAll header names are lowercase.
\nresponse.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headerNames = response.getHeaderNames();\n// headerNames === ['foo', 'set-cookie']\nReturns a shallow copy of the current outgoing headers. Since a shallow copy\nis used, array values may be mutated without additional calls to various\nheader-related http module methods. The keys of the returned object are the\nheader names and the values are the respective header values. All header names\nare lowercase.
\nThe object returned by the response.getHeaders() method does not\nprototypically inherit from the JavaScript Object. This means that typical\nObject methods such as obj.toString(), obj.hasOwnProperty(), and others\nare not defined and will not work.
response.setHeader('Foo', 'bar');\nresponse.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);\n\nconst headers = response.getHeaders();\n// headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }\nReturns true if the header identified by name is currently set in the\noutgoing headers. Note that the header name matching is case-insensitive.
const hasContentType = response.hasHeader('content-type');\nRemoves a header that has been queued for implicit sending.
\nresponse.removeHeader('Content-Encoding');\nSets a single header value for implicit headers. If this header already exists\nin the to-be-sent headers, its value will be replaced. Use an array of strings\nhere to send multiple headers with the same name.
\nresponse.setHeader('Content-Type', 'text/html');\nor
\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
When headers have been set with response.setHeader(), they will be merged\nwith any headers passed to response.writeHead(), with the headers passed\nto response.writeHead() given precedence.
// returns content-type = text/plain\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\nSets the Http2Stream's timeout value to msecs. If a callback is\nprovided, then it is added as a listener on the 'timeout' event on\nthe response object.
If no 'timeout' listener is added to the request, the response, or\nthe server, then Http2Streams are destroyed when they time out. If a\nhandler is assigned to the request, the response, or the server's 'timeout'\nevents, timed out sockets must be handled explicitly.
If this method is called and response.writeHead() has not been called,\nit will switch to implicit header mode and flush the implicit headers.
This sends a chunk of the response body. This method may\nbe called multiple times to provide successive parts of the body.
\nNote that in the http module, the response body is omitted when the\nrequest is a HEAD request. Similarly, the 204 and 304 responses\nmust not include a message body.
chunk can be a string or a buffer. If chunk is a string,\nthe second parameter specifies how to encode it into a byte stream.\nBy default the encoding is 'utf8'. callback will be called when this chunk\nof data is flushed.
This is the raw HTTP body and has nothing to do with higher-level multi-part\nbody encodings that may be used.
\nThe first time response.write() is called, it will send the buffered\nheader information and the first chunk of the body to the client. The second\ntime response.write() is called, Node.js assumes data will be streamed,\nand sends the new data separately. That is, the response is buffered up to the\nfirst chunk of the body.
Returns true if the entire data was flushed successfully to the kernel\nbuffer. Returns false if all or part of the data was queued in user memory.\n'drain' will be emitted when the buffer is free again.
Sends a status 100 Continue to the client, indicating that the request body\nshould be sent. See the 'checkContinue' event on Http2Server and\nHttp2SecureServer.
Sends a response header to the request. The status code is a 3-digit HTTP\nstatus code, like 404. The last argument, headers, are the response headers.
Returns a reference to the Http2ServerResponse, so that calls can be chained.
For compatibility with HTTP/1, a human-readable statusMessage may be\npassed as the second argument. However, because the statusMessage has no\nmeaning within HTTP/2, the argument will have no effect and a process warning\nwill be emitted.
const body = 'hello world';\nresponse.writeHead(200, {\n 'Content-Length': Buffer.byteLength(body),\n 'Content-Type': 'text/plain' });\nNote that Content-Length is given in bytes not characters. The\nBuffer.byteLength() API may be used to determine the number of bytes in a\ngiven encoding. On outbound messages, Node.js does not check if Content-Length\nand the length of the body being transmitted are equal or not. However, when\nreceiving messages, Node.js will automatically reject messages when the\nContent-Length does not match the actual payload size.
This method may be called at most one time on a message before\nresponse.end() is called.
If response.write() or response.end() are called before calling\nthis, the implicit/mutable headers will be calculated and call this function.
When headers have been set with response.setHeader(), they will be merged\nwith any headers passed to response.writeHead(), with the headers passed\nto response.writeHead() given precedence.
// returns content-type = text/plain\nconst server = http2.createServer((req, res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, { 'Content-Type': 'text/plain' });\n res.end('ok');\n});\nAttempting to set a header field name or value that contains invalid characters\nwill result in a TypeError being thrown.
Call http2stream.pushStream() with the given headers, and wrap the\ngiven Http2Stream on a newly created Http2ServerResponse as the callback\nparameter if successful. When Http2ServerRequest is closed, the callback is\ncalled with an error ERR_HTTP2_INVALID_STREAM.
See response.socket.
Boolean value that indicates whether the response has completed. Starts\nas false. After response.end() executes, the value will be true.
True if headers were sent, false otherwise (read-only).
" }, { "textRaw": "`sendDate` {boolean}", "type": "boolean", "name": "sendDate", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "When true, the Date header will be automatically generated and sent in\nthe response if it is not already present in the headers. Defaults to true.
\nThis should only be disabled for testing; HTTP requires the Date header\nin responses.
" }, { "textRaw": "`socket` {net.Socket|tls.TLSSocket}", "type": "net.Socket|tls.TLSSocket", "name": "socket", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Returns a Proxy object that acts as a net.Socket (or tls.TLSSocket) but\napplies getters, setters, and methods based on HTTP/2 logic.
destroyed, readable, and writable properties will be retrieved from and\nset on response.stream.
destroy, emit, end, on and once methods will be called on\nresponse.stream.
setTimeout method will be called on response.stream.session.
pause, read, resume, and write will throw an error with code\nERR_HTTP2_NO_SOCKET_MANIPULATION. See Http2Session and Sockets for\nmore information.
All other interactions will be routed directly to the socket.
\nconst http2 = require('http2');\nconst server = http2.createServer((req, res) => {\n const ip = req.socket.remoteAddress;\n const port = req.socket.remotePort;\n res.end(`Your IP address is ${ip} and your source port is ${port}.`);\n}).listen(3000);\nWhen using implicit headers (not calling response.writeHead() explicitly),\nthis property controls the status code that will be sent to the client when\nthe headers get flushed.
response.statusCode = 404;\nAfter response header was sent to the client, this property indicates the\nstatus code which was sent out.
" }, { "textRaw": "`statusMessage` {string}", "type": "string", "name": "statusMessage", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "Status message is not supported by HTTP/2 (RFC7540 8.1.2.4). It returns\nan empty string.
" }, { "textRaw": "`stream` {Http2Stream}", "type": "Http2Stream", "name": "stream", "meta": { "added": [ "v8.4.0" ], "changes": [] }, "desc": "The Http2Stream object backing the response.
The Performance Observer API can be used to collect basic performance\nmetrics for each Http2Session and Http2Stream instance.
const { PerformanceObserver } = require('perf_hooks');\n\nconst obs = new PerformanceObserver((items) => {\n const entry = items.getEntries()[0];\n console.log(entry.entryType); // prints 'http2'\n if (entry.name === 'Http2Session') {\n // entry contains statistics about the Http2Session\n } else if (entry.name === 'Http2Stream') {\n // entry contains statistics about the Http2Stream\n }\n});\nobs.observe({ entryTypes: ['http2'] });\nThe entryType property of the PerformanceEntry will be equal to 'http2'.
The name property of the PerformanceEntry will be equal to either\n'Http2Stream' or 'Http2Session'.
If name is equal to Http2Stream, the PerformanceEntry will contain the\nfollowing additional properties:
bytesRead <number> The number of DATA frame bytes received for this\nHttp2Stream.bytesWritten <number> The number of DATA frame bytes sent for this\nHttp2Stream.id <number> The identifier of the associated Http2StreamtimeToFirstByte <number> The number of milliseconds elapsed between the\nPerformanceEntry startTime and the reception of the first DATA frame.timeToFirstByteSent <number> The number of milliseconds elapsed between\nthe PerformanceEntry startTime and sending of the first DATA frame.timeToFirstHeader <number> The number of milliseconds elapsed between the\nPerformanceEntry startTime and the reception of the first header.If name is equal to Http2Session, the PerformanceEntry will contain the\nfollowing additional properties:
bytesRead <number> The number of bytes received for this Http2Session.bytesWritten <number> The number of bytes sent for this Http2Session.framesReceived <number> The number of HTTP/2 frames received by the\nHttp2Session.framesSent <number> The number of HTTP/2 frames sent by the Http2Session.maxConcurrentStreams <number> The maximum number of streams concurrently\nopen during the lifetime of the Http2Session.pingRTT <number> The number of milliseconds elapsed since the transmission\nof a PING frame and the reception of its acknowledgment. Only present if\na PING frame has been sent on the Http2Session.streamAverageDuration <number> The average duration (in milliseconds) for\nall Http2Stream instances.streamCount <number> The number of Http2Stream instances processed by\nthe Http2Session.type <string> Either 'server' or 'client' to identify the type of\nHttp2Session.HTTPS is the HTTP protocol over TLS/SSL. In Node.js this is implemented as a\nseparate module.
", "classes": [ { "textRaw": "Class: https.Agent", "type": "class", "name": "https.Agent", "meta": { "added": [ "v0.4.5" ], "changes": [] }, "desc": "An Agent object for HTTPS similar to http.Agent. See\nhttps.request() for more information.
This class is a subclass of tls.Server and emits events same as\nhttp.Server. See http.Server for more information.
See server.close() from the HTTP module for details.
Starts the HTTPS server listening for encrypted connections.\nThis method is identical to server.listen() from net.Server.
See http.Server#maxHeadersCount.
See http.Server#headersTimeout.
See http.Server#timeout.
See http.Server#keepAliveTimeout.
// curl -k https://localhost:8000/\nconst https = require('https');\nconst fs = require('fs');\n\nconst options = {\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);\nOr
\nconst https = require('https');\nconst fs = require('fs');\n\nconst options = {\n pfx: fs.readFileSync('test/fixtures/test_cert.pfx'),\n passphrase: 'sample'\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);\nLike http.get() but for HTTPS.
options can be an object, a string, or a URL object. If options is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
const https = require('https');\n\nhttps.get('https://encrypted.google.com/', (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n\n}).on('error', (e) => {\n console.error(e);\n});\nLike http.get() but for HTTPS.
options can be an object, a string, or a URL object. If options is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
const https = require('https');\n\nhttps.get('https://encrypted.google.com/', (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n\n}).on('error', (e) => {\n console.error(e);\n});\nMakes a request to a secure web server.
\nThe following additional options from tls.connect() are also accepted:\nca, cert, ciphers, clientCertEngine, crl, dhparam, ecdhCurve,\nhonorCipherOrder, key, passphrase, pfx, rejectUnauthorized,\nsecureOptions, secureProtocol, servername, sessionIdContext.
options can be an object, a string, or a URL object. If options is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
const https = require('https');\n\nconst options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET'\n};\n\nconst req = https.request(options, (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n});\n\nreq.on('error', (e) => {\n console.error(e);\n});\nreq.end();\nExample using options from tls.connect():
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')\n};\noptions.agent = new https.Agent(options);\n\nconst req = https.request(options, (res) => {\n // ...\n});\nAlternatively, opt out of connection pooling by not using an Agent.
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n agent: false\n};\n\nconst req = https.request(options, (res) => {\n // ...\n});\nExample using a URL as options:
const options = new URL('https://abc:xyz@example.com');\n\nconst req = https.request(options, (res) => {\n // ...\n});\nExample pinning on certificate fingerprint, or the public key (similar to\npin-sha256):
const tls = require('tls');\nconst https = require('https');\nconst crypto = require('crypto');\n\nfunction sha256(s) {\n return crypto.createHash('sha256').update(s).digest('base64');\n}\nconst options = {\n hostname: 'github.com',\n port: 443,\n path: '/',\n method: 'GET',\n checkServerIdentity: function(host, cert) {\n // Make sure the certificate is issued to the host we are connected to\n const err = tls.checkServerIdentity(host, cert);\n if (err) {\n return err;\n }\n\n // Pin the public key, similar to HPKP pin-sha25 pinning\n const pubkey256 = 'pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=';\n if (sha256(cert.pubkey) !== pubkey256) {\n const msg = 'Certificate verification error: ' +\n `The public key of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // Pin the exact certificate, rather then the pub key\n const cert256 = '25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:' +\n 'D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16';\n if (cert.fingerprint256 !== cert256) {\n const msg = 'Certificate verification error: ' +\n `The certificate of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // This loop is informational only.\n // Print the certificate and public key fingerprints of all certs in the\n // chain. Its common to pin the public key of the issuer on the public\n // internet, while pinning the public key of the service in sensitive\n // environments.\n do {\n console.log('Subject Common Name:', cert.subject.CN);\n console.log(' Certificate SHA256 fingerprint:', cert.fingerprint256);\n\n hash = crypto.createHash('sha256');\n console.log(' Public key ping-sha256:', sha256(cert.pubkey));\n\n lastprint256 = cert.fingerprint256;\n cert = cert.issuerCertificate;\n } while (cert.fingerprint256 !== lastprint256);\n\n },\n};\n\noptions.agent = new https.Agent(options);\nconst req = https.request(options, (res) => {\n console.log('All OK. Server matched our pinned cert or public key');\n console.log('statusCode:', res.statusCode);\n // Print the HPKP values\n console.log('headers:', res.headers['public-key-pins']);\n\n res.on('data', (d) => {});\n});\n\nreq.on('error', (e) => {\n console.error(e.message);\n});\nreq.end();\nOutputs for example:
\nSubject Common Name: github.com\n Certificate SHA256 fingerprint: 25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16\n Public key ping-sha256: pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=\nSubject Common Name: DigiCert SHA2 Extended Validation Server CA\n Certificate SHA256 fingerprint: 40:3E:06:2A:26:53:05:91:13:28:5B:AF:80:A0:D4:AE:42:2C:84:8C:9F:78:FA:D0:1F:C9:4B:C5:B8:7F:EF:1A\n Public key ping-sha256: RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\nSubject Common Name: DigiCert High Assurance EV Root CA\n Certificate SHA256 fingerprint: 74:31:E5:F4:C3:C1:CE:46:90:77:4F:0B:61:E0:54:40:88:3B:A9:A0:1E:D0:0B:A6:AB:D7:80:6E:D3:B1:18:CF\n Public key ping-sha256: WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\nAll OK. Server matched our pinned cert or public key\nstatusCode: 200\nheaders: max-age=0; pin-sha256=\"WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\"; pin-sha256=\"RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\"; pin-sha256=\"k2v657xBsOVe1PQRwOsHsw3bsGT2VzIqz5K+59sNQws=\"; pin-sha256=\"K87oWBWM9UZfyddvDfoxL+8lpNyoUB2ptGtn0fv6G2Q=\"; pin-sha256=\"IQBnNBEiFuhj+8x6X8XLgh01V9Ic5/V3IRQLNFFc7v4=\"; pin-sha256=\"iie1VXtL7HzAMF+/PVPR9xzT80kQxdZeJ+zduCB3uj0=\"; pin-sha256=\"LvRiGEjRqfzurezaWuj8Wie2gyHMrW5Q06LspMnox7A=\"; includeSubDomains\nMakes a request to a secure web server.
\nThe following additional options from tls.connect() are also accepted:\nca, cert, ciphers, clientCertEngine, crl, dhparam, ecdhCurve,\nhonorCipherOrder, key, passphrase, pfx, rejectUnauthorized,\nsecureOptions, secureProtocol, servername, sessionIdContext.
options can be an object, a string, or a URL object. If options is a\nstring, it is automatically parsed with url.parse(). If it is a URL\nobject, it will be automatically converted to an ordinary options object.
const https = require('https');\n\nconst options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET'\n};\n\nconst req = https.request(options, (res) => {\n console.log('statusCode:', res.statusCode);\n console.log('headers:', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n});\n\nreq.on('error', (e) => {\n console.error(e);\n});\nreq.end();\nExample using options from tls.connect():
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')\n};\noptions.agent = new https.Agent(options);\n\nconst req = https.request(options, (res) => {\n // ...\n});\nAlternatively, opt out of connection pooling by not using an Agent.
const options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n agent: false\n};\n\nconst req = https.request(options, (res) => {\n // ...\n});\nExample using a URL as options:
const options = new URL('https://abc:xyz@example.com');\n\nconst req = https.request(options, (res) => {\n // ...\n});\nExample pinning on certificate fingerprint, or the public key (similar to\npin-sha256):
const tls = require('tls');\nconst https = require('https');\nconst crypto = require('crypto');\n\nfunction sha256(s) {\n return crypto.createHash('sha256').update(s).digest('base64');\n}\nconst options = {\n hostname: 'github.com',\n port: 443,\n path: '/',\n method: 'GET',\n checkServerIdentity: function(host, cert) {\n // Make sure the certificate is issued to the host we are connected to\n const err = tls.checkServerIdentity(host, cert);\n if (err) {\n return err;\n }\n\n // Pin the public key, similar to HPKP pin-sha25 pinning\n const pubkey256 = 'pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=';\n if (sha256(cert.pubkey) !== pubkey256) {\n const msg = 'Certificate verification error: ' +\n `The public key of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // Pin the exact certificate, rather then the pub key\n const cert256 = '25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:' +\n 'D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16';\n if (cert.fingerprint256 !== cert256) {\n const msg = 'Certificate verification error: ' +\n `The certificate of '${cert.subject.CN}' ` +\n 'does not match our pinned fingerprint';\n return new Error(msg);\n }\n\n // This loop is informational only.\n // Print the certificate and public key fingerprints of all certs in the\n // chain. Its common to pin the public key of the issuer on the public\n // internet, while pinning the public key of the service in sensitive\n // environments.\n do {\n console.log('Subject Common Name:', cert.subject.CN);\n console.log(' Certificate SHA256 fingerprint:', cert.fingerprint256);\n\n hash = crypto.createHash('sha256');\n console.log(' Public key ping-sha256:', sha256(cert.pubkey));\n\n lastprint256 = cert.fingerprint256;\n cert = cert.issuerCertificate;\n } while (cert.fingerprint256 !== lastprint256);\n\n },\n};\n\noptions.agent = new https.Agent(options);\nconst req = https.request(options, (res) => {\n console.log('All OK. Server matched our pinned cert or public key');\n console.log('statusCode:', res.statusCode);\n // Print the HPKP values\n console.log('headers:', res.headers['public-key-pins']);\n\n res.on('data', (d) => {});\n});\n\nreq.on('error', (e) => {\n console.error(e.message);\n});\nreq.end();\nOutputs for example:
\nSubject Common Name: github.com\n Certificate SHA256 fingerprint: 25:FE:39:32:D9:63:8C:8A:FC:A1:9A:29:87:D8:3E:4C:1D:98:DB:71:E4:1A:48:03:98:EA:22:6A:BD:8B:93:16\n Public key ping-sha256: pL1+qb9HTMRZJmuC/bB/ZI9d302BYrrqiVuRyW+DGrU=\nSubject Common Name: DigiCert SHA2 Extended Validation Server CA\n Certificate SHA256 fingerprint: 40:3E:06:2A:26:53:05:91:13:28:5B:AF:80:A0:D4:AE:42:2C:84:8C:9F:78:FA:D0:1F:C9:4B:C5:B8:7F:EF:1A\n Public key ping-sha256: RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\nSubject Common Name: DigiCert High Assurance EV Root CA\n Certificate SHA256 fingerprint: 74:31:E5:F4:C3:C1:CE:46:90:77:4F:0B:61:E0:54:40:88:3B:A9:A0:1E:D0:0B:A6:AB:D7:80:6E:D3:B1:18:CF\n Public key ping-sha256: WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\nAll OK. Server matched our pinned cert or public key\nstatusCode: 200\nheaders: max-age=0; pin-sha256=\"WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18=\"; pin-sha256=\"RRM1dGqnDFsCJXBTHky16vi1obOlCgFFn/yOhI/y+ho=\"; pin-sha256=\"k2v657xBsOVe1PQRwOsHsw3bsGT2VzIqz5K+59sNQws=\"; pin-sha256=\"K87oWBWM9UZfyddvDfoxL+8lpNyoUB2ptGtn0fv6G2Q=\"; pin-sha256=\"IQBnNBEiFuhj+8x6X8XLgh01V9Ic5/V3IRQLNFFc7v4=\"; pin-sha256=\"iie1VXtL7HzAMF+/PVPR9xzT80kQxdZeJ+zduCB3uj0=\"; pin-sha256=\"LvRiGEjRqfzurezaWuj8Wie2gyHMrW5Q06LspMnox7A=\"; includeSubDomains\nGlobal instance of https.Agent for all HTTPS client requests.
The inspector module provides an API for interacting with the V8 inspector.
It can be accessed using:
\nconst inspector = require('inspector');\nDeactivate the inspector. Blocks until there are no active connections.
" }, { "textRaw": "inspector.open([port[, host[, wait]]])", "type": "method", "name": "open", "signatures": [ { "params": [ { "textRaw": "`port` {number} Port to listen on for inspector connections. Optional. **Default:** what was specified on the CLI.", "name": "port", "type": "number", "default": "what was specified on the CLI", "desc": "Port to listen on for inspector connections. Optional.", "optional": true }, { "textRaw": "`host` {string} Host to listen on for inspector connections. Optional. **Default:** what was specified on the CLI.", "name": "host", "type": "string", "default": "what was specified on the CLI", "desc": "Host to listen on for inspector connections. Optional.", "optional": true }, { "textRaw": "`wait` {boolean} Block until a client has connected. Optional. **Default:** `false`.", "name": "wait", "type": "boolean", "default": "`false`", "desc": "Block until a client has connected. Optional.", "optional": true } ] } ], "desc": "Activate inspector on host and port. Equivalent to node --inspect=[[host:]port], but can be done programmatically after node has\nstarted.
If wait is true, will block until a client has connected to the inspect port\nand flow control has been passed to the debugger client.
See the security warning regarding the host\nparameter usage.
Return the URL of the active inspector, or undefined if there is none.
require('inspector').console.log('a message');\nThe inspector console does not have API parity with Node.js\nconsole.
", "shortDesc": "An object to send messages to the remote inspector console." } ], "classes": [ { "textRaw": "Class: inspector.Session", "type": "class", "name": "inspector.Session", "desc": "The inspector.Session is used for dispatching messages to the V8 inspector\nback-end and receiving message responses and notifications.
Emitted when any notification from the V8 Inspector is received.
\nsession.on('inspectorNotification', (message) => console.log(message.method));\n// Debugger.paused\n// Debugger.resumed\nIt is also possible to subscribe only to notifications with specific method:
" }, { "textRaw": "Event:Emitted when an inspector notification is received that has its method field set\nto the <inspector-protocol-method> value.
The following snippet installs a listener on the 'Debugger.paused'\nevent, and prints the reason for program suspension whenever program\nexecution is suspended (through breakpoints, for example):
session.on('Debugger.paused', ({ params }) => {\n console.log(params.hitBreakpoints);\n});\n// [ '/the/file/that/has/the/breakpoint.js:11:0' ]\nConnects a session to the inspector back-end. An exception will be thrown\nif there is already a connected session established either through the API or by\na front-end connected to the Inspector WebSocket port.
" }, { "textRaw": "session.disconnect()", "type": "method", "name": "disconnect", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Immediately close the session. All pending message callbacks will be called\nwith an error. session.connect() will need to be called to be able to send\nmessages again. Reconnected session will lose all inspector state, such as\nenabled agents or configured breakpoints.
Posts a message to the inspector back-end. callback will be notified when\na response is received. callback is a function that accepts two optional\narguments - error and message-specific result.
session.post('Runtime.evaluate', { expression: '2 + 2' },\n (error, { result }) => console.log(result));\n// Output: { type: 'number', value: 4, description: '4' }\nThe latest version of the V8 inspector protocol is published on the\nChrome DevTools Protocol Viewer.
\nNode.js inspector supports all the Chrome DevTools Protocol domains declared\nby V8. Chrome DevTools Protocol domain provides an interface for interacting\nwith one of the runtime agents used to inspect the application state and listen\nto the run-time events.
\nApart from the debugger, various V8 Profilers are available through the DevTools\nprotocol.
" } ], "modules": [ { "textRaw": "CPU Profiler", "name": "cpu_profiler", "desc": "Here's an example showing how to use the CPU Profiler:
\nconst inspector = require('inspector');\nconst fs = require('fs');\nconst session = new inspector.Session();\nsession.connect();\n\nsession.post('Profiler.enable', () => {\n session.post('Profiler.start', () => {\n // invoke business logic under measurement here...\n\n // some time later...\n session.post('Profiler.stop', (err, { profile }) => {\n // write profile to disk, upload, etc.\n if (!err) {\n fs.writeFileSync('./profile.cpuprofile', JSON.stringify(profile));\n }\n });\n });\n});\nHere's an example showing how to use the Heap Profiler:
\nconst inspector = require('inspector');\nconst fs = require('fs');\nconst session = new inspector.Session();\n\nconst fd = fs.openSync('profile.heapsnapshot', 'w');\n\nsession.connect();\n\nsession.on('HeapProfiler.addHeapSnapshotChunk', (m) => {\n fs.writeSync(fd, m.params.chunk);\n});\n\nsession.post('HeapProfiler.takeHeapSnapshot', null, (err, r) => {\n console.log('Runtime.takeHeapSnapshot done:', err, r);\n session.disconnect();\n fs.closeSync(fd);\n});\nCreate a new instance of the inspector.Session class. The inspector session\nneeds to be connected through session.connect() before the messages\ncan be dispatched to the inspector backend.
inspector.Session is an EventEmitter with the following events:
In the Node.js module system, each file is treated as a separate module. For\nexample, consider a file named foo.js:
const circle = require('./circle.js');\nconsole.log(`The area of a circle of radius 4 is ${circle.area(4)}`);\nOn the first line, foo.js loads the module circle.js that is in the same\ndirectory as foo.js.
Here are the contents of circle.js:
const { PI } = Math;\n\nexports.area = (r) => PI * r ** 2;\n\nexports.circumference = (r) => 2 * PI * r;\nThe module circle.js has exported the functions area() and\ncircumference(). Functions and objects are added to the root of a module\nby specifying additional properties on the special exports object.
Variables local to the module will be private, because the module is wrapped\nin a function by Node.js (see module wrapper).\nIn this example, the variable PI is private to circle.js.
The module.exports property can be assigned a new value (such as a function\nor object).
Below, bar.js makes use of the square module, which exports a Square class:
const Square = require('./square.js');\nconst mySquare = new Square(2);\nconsole.log(`The area of mySquare is ${mySquare.area()}`);\nThe square module is defined in square.js:
// assigning to exports will not modify module, must use module.exports\nmodule.exports = class Square {\n constructor(width) {\n this.width = width;\n }\n\n area() {\n return this.width ** 2;\n }\n};\nThe module system is implemented in the require('module') module.
When a file is run directly from Node.js, require.main is set to its\nmodule. That means that it is possible to determine whether a file has been\nrun directly by testing require.main === module.
For a file foo.js, this will be true if run via node foo.js, but\nfalse if run by require('./foo').
Because module provides a filename property (normally equivalent to\n__filename), the entry point of the current application can be obtained\nby checking require.main.filename.
The semantics of Node.js's require() function were designed to be general\nenough to support a number of reasonable directory structures. Package manager\nprograms such as dpkg, rpm, and npm will hopefully find it possible to\nbuild native packages from Node.js modules without modification.
Below we give a suggested directory structure that could work:
\nLet's say that we wanted to have the folder at\n/usr/lib/node/<some-package>/<some-version> hold the contents of a\nspecific version of a package.
Packages can depend on one another. In order to install package foo, it\nmay be necessary to install a specific version of package bar. The bar\npackage may itself have dependencies, and in some cases, these may even collide\nor form cyclic dependencies.
Since Node.js looks up the realpath of any modules it loads (that is,\nresolves symlinks), and then looks for their dependencies in the node_modules\nfolders as described here, this\nsituation is very simple to resolve with the following architecture:
/usr/lib/node/foo/1.2.3/ - Contents of the foo package, version 1.2.3./usr/lib/node/bar/4.3.2/ - Contents of the bar package that foo\ndepends on./usr/lib/node/foo/1.2.3/node_modules/bar - Symbolic link to\n/usr/lib/node/bar/4.3.2/./usr/lib/node/bar/4.3.2/node_modules/* - Symbolic links to the packages\nthat bar depends on.Thus, even if a cycle is encountered, or if there are dependency\nconflicts, every module will be able to get a version of its dependency\nthat it can use.
\nWhen the code in the foo package does require('bar'), it will get the\nversion that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar.\nThen, when the code in the bar package calls require('quux'), it'll get\nthe version that is symlinked into\n/usr/lib/node/bar/4.3.2/node_modules/quux.
Furthermore, to make the module lookup process even more optimal, rather\nthan putting packages directly in /usr/lib/node, we could put them in\n/usr/lib/node_modules/<name>/<version>. Then Node.js will not bother\nlooking for missing dependencies in /usr/node_modules or /node_modules.
In order to make modules available to the Node.js REPL, it might be useful to\nalso add the /usr/lib/node_modules folder to the $NODE_PATH environment\nvariable. Since the module lookups using node_modules folders are all\nrelative, and based on the real path of the files making the calls to\nrequire(), the packages themselves can be anywhere.
To get the exact filename that will be loaded when require() is called, use\nthe require.resolve() function.
Putting together all of the above, here is the high-level algorithm\nin pseudocode of what require.resolve() does:
require(X) from module at path Y\n1. If X is a core module,\n a. return the core module\n b. STOP\n2. If X begins with '/'\n a. set Y to be the filesystem root\n3. If X begins with './' or '/' or '../'\n a. LOAD_AS_FILE(Y + X)\n b. LOAD_AS_DIRECTORY(Y + X)\n4. LOAD_NODE_MODULES(X, dirname(Y))\n5. THROW \"not found\"\n\nLOAD_AS_FILE(X)\n1. If X is a file, load X as JavaScript text. STOP\n2. If X.js is a file, load X.js as JavaScript text. STOP\n3. If X.json is a file, parse X.json to a JavaScript Object. STOP\n4. If X.node is a file, load X.node as binary addon. STOP\n\nLOAD_INDEX(X)\n1. If X/index.js is a file, load X/index.js as JavaScript text. STOP\n2. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP\n3. If X/index.node is a file, load X/index.node as binary addon. STOP\n\nLOAD_AS_DIRECTORY(X)\n1. If X/package.json is a file,\n a. Parse X/package.json, and look for \"main\" field.\n b. let M = X + (json main field)\n c. LOAD_AS_FILE(M)\n d. LOAD_INDEX(M)\n2. LOAD_INDEX(X)\n\nLOAD_NODE_MODULES(X, START)\n1. let DIRS = NODE_MODULES_PATHS(START)\n2. for each DIR in DIRS:\n a. LOAD_AS_FILE(DIR/X)\n b. LOAD_AS_DIRECTORY(DIR/X)\n\nNODE_MODULES_PATHS(START)\n1. let PARTS = path split(START)\n2. let I = count of PARTS - 1\n3. let DIRS = [GLOBAL_FOLDERS]\n4. while I >= 0,\n a. if PARTS[I] = \"node_modules\" CONTINUE\n b. DIR = path join(PARTS[0 .. I] + \"node_modules\")\n c. DIRS = DIRS + DIR\n d. let I = I - 1\n5. return DIRS\nModules are cached after the first time they are loaded. This means\n(among other things) that every call to require('foo') will get\nexactly the same object returned, if it would resolve to the same file.
Provided require.cache is not modified, multiple calls to\nrequire('foo') will not cause the module code to be executed multiple times.\nThis is an important feature. With it, \"partially done\" objects can be returned,\nthus allowing transitive dependencies to be loaded even when they would cause\ncycles.
To have a module execute code multiple times, export a function, and call\nthat function.
", "miscs": [ { "textRaw": "Module Caching Caveats", "name": "Module Caching Caveats", "type": "misc", "desc": "Modules are cached based on their resolved filename. Since modules may\nresolve to a different filename based on the location of the calling\nmodule (loading from node_modules folders), it is not a guarantee\nthat require('foo') will always return the exact same object, if it\nwould resolve to different files.
Additionally, on case-insensitive file systems or operating systems, different\nresolved filenames can point to the same file, but the cache will still treat\nthem as different modules and will reload the file multiple times. For example,\nrequire('./foo') and require('./FOO') return two different objects,\nirrespective of whether or not ./foo and ./FOO are the same file.
Node.js has several modules compiled into the binary. These modules are\ndescribed in greater detail elsewhere in this documentation.
\nThe core modules are defined within Node.js's source and are located in the\nlib/ folder.
Core modules are always preferentially loaded if their identifier is\npassed to require(). For instance, require('http') will always\nreturn the built in HTTP module, even if there is a file by that name.
When there are circular require() calls, a module might not have finished\nexecuting when it is returned.
Consider this situation:
\na.js:
console.log('a starting');\nexports.done = false;\nconst b = require('./b.js');\nconsole.log('in a, b.done = %j', b.done);\nexports.done = true;\nconsole.log('a done');\nb.js:
console.log('b starting');\nexports.done = false;\nconst a = require('./a.js');\nconsole.log('in b, a.done = %j', a.done);\nexports.done = true;\nconsole.log('b done');\nmain.js:
console.log('main starting');\nconst a = require('./a.js');\nconst b = require('./b.js');\nconsole.log('in main, a.done = %j, b.done = %j', a.done, b.done);\nWhen main.js loads a.js, then a.js in turn loads b.js. At that\npoint, b.js tries to load a.js. In order to prevent an infinite\nloop, an unfinished copy of the a.js exports object is returned to the\nb.js module. b.js then finishes loading, and its exports object is\nprovided to the a.js module.
By the time main.js has loaded both modules, they're both finished.\nThe output of this program would thus be:
$ node main.js\nmain starting\na starting\nb starting\nin b, a.done = false\nb done\nin a, b.done = true\na done\nin main, a.done = true, b.done = true\nCareful planning is required to allow cyclic module dependencies to work\ncorrectly within an application.
" }, { "textRaw": "File Modules", "name": "File Modules", "type": "misc", "desc": "If the exact filename is not found, then Node.js will attempt to load the\nrequired filename with the added extensions: .js, .json, and finally\n.node.
.js files are interpreted as JavaScript text files, and .json files are\nparsed as JSON text files. .node files are interpreted as compiled addon\nmodules loaded with dlopen.
A required module prefixed with '/' is an absolute path to the file. For\nexample, require('/home/marco/foo.js') will load the file at\n/home/marco/foo.js.
A required module prefixed with './' is relative to the file calling\nrequire(). That is, circle.js must be in the same directory as foo.js for\nrequire('./circle') to find it.
Without a leading '/', './', or '../' to indicate a file, the module must\neither be a core module or is loaded from a node_modules folder.
If the given path does not exist, require() will throw an Error with its\ncode property set to 'MODULE_NOT_FOUND'.
It is convenient to organize programs and libraries into self-contained\ndirectories, and then provide a single entry point to that library.\nThere are three ways in which a folder may be passed to require() as\nan argument.
The first is to create a package.json file in the root of the folder,\nwhich specifies a main module. An example package.json file might\nlook like this:
{ \"name\" : \"some-library\",\n \"main\" : \"./lib/some-library.js\" }\nIf this was in a folder at ./some-library, then\nrequire('./some-library') would attempt to load\n./some-library/lib/some-library.js.
This is the extent of Node.js's awareness of package.json files.
If there is no package.json file present in the directory, or if the\n'main' entry is missing or cannot be resolved, then Node.js\nwill attempt to load an index.js or index.node file out of that\ndirectory. For example, if there was no package.json file in the above\nexample, then require('./some-library') would attempt to load:
./some-library/index.js./some-library/index.nodeIf these attempts fail, then Node.js will report the entire module as missing\nwith the default error:
\nError: Cannot find module 'some-library'\nIf the module identifier passed to require() is not a\ncore module, and does not begin with '/', '../', or\n'./', then Node.js starts at the parent directory of the current module, and\nadds /node_modules, and attempts to load the module from that location.\nNode.js will not append node_modules to a path already ending in\nnode_modules.
If it is not found there, then it moves to the parent directory, and so\non, until the root of the file system is reached.
\nFor example, if the file at '/home/ry/projects/foo.js' called\nrequire('bar.js'), then Node.js would look in the following locations, in\nthis order:
/home/ry/projects/node_modules/bar.js/home/ry/node_modules/bar.js/home/node_modules/bar.js/node_modules/bar.jsThis allows programs to localize their dependencies, so that they do not\nclash.
\nIt is possible to require specific files or sub modules distributed with a\nmodule by including a path suffix after the module name. For instance\nrequire('example-module/path/to/file') would resolve path/to/file\nrelative to where example-module is located. The suffixed path follows the\nsame module resolution semantics.
If the NODE_PATH environment variable is set to a colon-delimited list\nof absolute paths, then Node.js will search those paths for modules if they\nare not found elsewhere.
On Windows, NODE_PATH is delimited by semicolons (;) instead of colons.
NODE_PATH was originally created to support loading modules from\nvarying paths before the current module resolution algorithm was frozen.
NODE_PATH is still supported, but is less necessary now that the Node.js\necosystem has settled on a convention for locating dependent modules.\nSometimes deployments that rely on NODE_PATH show surprising behavior\nwhen people are unaware that NODE_PATH must be set. Sometimes a\nmodule's dependencies change, causing a different version (or even a\ndifferent module) to be loaded as the NODE_PATH is searched.
Additionally, Node.js will search in the following list of GLOBAL_FOLDERS:
\n$HOME/.node_modules$HOME/.node_libraries$PREFIX/lib/nodeWhere $HOME is the user's home directory, and $PREFIX is Node.js's\nconfigured node_prefix.
These are mostly for historic reasons.
\nIt is strongly encouraged to place dependencies in the local node_modules\nfolder. These will be loaded faster, and more reliably.
Before a module's code is executed, Node.js will wrap it with a function\nwrapper that looks like the following:
\n(function(exports, require, module, __filename, __dirname) {\n// Module code actually lives in here\n});\nBy doing this, Node.js achieves a few things:
\nvar, const or let) scoped to\nthe module rather than the global object.It helps to provide some global-looking variables that are actually specific\nto the module, such as:
\nmodule and exports objects that the implementor can use to export\nvalues from the module.__filename and __dirname, containing the\nmodule's absolute filename and directory path.The directory name of the current module. This is the same as the\npath.dirname() of the __filename.
Example: running node example.js from /Users/mjr
console.log(__dirname);\n// Prints: /Users/mjr\nconsole.log(path.dirname(__filename));\n// Prints: /Users/mjr\nThe file name of the current module. This is the current module file's absolute\npath with symlinks resolved.
\nFor a main program this is not necessarily the same as the file name used in the\ncommand line.
\nSee __dirname for the directory name of the current module.
Examples:
\nRunning node example.js from /Users/mjr
console.log(__filename);\n// Prints: /Users/mjr/example.js\nconsole.log(__dirname);\n// Prints: /Users/mjr\nGiven two modules: a and b, where b is a dependency of\na and there is a directory structure of:
/Users/mjr/app/a.js/Users/mjr/app/node_modules/b/b.jsReferences to __filename within b.js will return\n/Users/mjr/app/node_modules/b/b.js while references to __filename within\na.js will return /Users/mjr/app/a.js.
A reference to the module.exports that is shorter to type.\nSee the section about the exports shortcut for details on when to use\nexports and when to use module.exports.
A reference to the current module, see the section about the\nmodule object. In particular, module.exports is used for defining what\na module exports and makes available through require().
Used to import modules, JSON, and local files. Modules can be imported\nfrom node_modules. Local modules and JSON files can be imported using\na relative path (e.g. ./, ./foo, ./bar/baz, ../foo) that will be\nresolved against the directory named by __dirname (if defined) or\nthe current working directory.
// Importing a local module:\nconst myLocalModule = require('./path/myLocalModule');\n\n// Importing a JSON file:\nconst jsonData = require('./path/filename.json');\n\n// Importing a module from node_modules or Node.js built-in module:\nconst crypto = require('crypto');\nModules are cached in this object when they are required. By deleting a key\nvalue from this object, the next require will reload the module. Note that\nthis does not apply to native addons, for which reloading will result in an\nerror.
Instruct require on how to handle certain file extensions.
Process files with the extension .sjs as .js:
require.extensions['.sjs'] = require.extensions['.js'];\nDeprecated In the past, this list has been used to load\nnon-JavaScript modules into Node.js by compiling them on-demand.\nHowever, in practice, there are much better ways to do this, such as\nloading modules via some other Node.js program, or compiling them to\nJavaScript ahead of time.
\nSince the module system is locked, this feature will probably never go\naway. However, it may have subtle bugs and complexities that are best\nleft untouched.
\nNote that the number of file system operations that the module system\nhas to perform in order to resolve a require(...) statement to a\nfilename scales linearly with the number of registered extensions.
In other words, adding extensions slows down the module loader and\nshould be discouraged.
" }, { "textRaw": "`main` {Object}", "type": "Object", "name": "main", "meta": { "added": [ "v0.1.17" ], "changes": [] }, "desc": "The Module object representing the entry script loaded when the Node.js\nprocess launched.\nSee \"Accessing the main module\".
In entry.js script:
console.log(require.main);\nnode entry.js\nModule {\n id: '.',\n exports: {},\n parent: null,\n filename: '/absolute/path/to/entry.js',\n loaded: false,\n children: [],\n paths:\n [ '/absolute/path/to/node_modules',\n '/absolute/path/node_modules',\n '/absolute/node_modules',\n '/node_modules' ] }\nUse the internal require() machinery to look up the location of a module,\nbut rather than loading the module, just return the resolved filename.
Returns an array containing the paths searched during resolution of request or\nnull if the request string references a core module, for example http or\nfs.
Provides general utility methods when interacting with instances of\nModule — the module variable often seen in file modules. Accessed\nvia require('module').
A list of the names of all modules provided by Node.js. Can be used to verify\nif a module is maintained by a third party or not.
\nNote that module in this context isn't the same object that's provided\nby the module wrapper. To access it, require the Module module:
const builtin = require('module').builtinModules;\nconst { createRequireFromPath } = require('module');\nconst requireUtil = createRequireFromPath('../src/utils');\n\n// require `../src/utils/some-tool`\nrequireUtil('./some-tool');\nIn each module, the module free variable is a reference to the object\nrepresenting the current module. For convenience, module.exports is\nalso accessible via the exports module-global. module is not actually\na global but rather local to each module.
The module objects required for the first time by this one.
" }, { "textRaw": "`exports` {Object}", "type": "Object", "name": "exports", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The module.exports object is created by the Module system. Sometimes this is\nnot acceptable; many want their module to be an instance of some class. To do\nthis, assign the desired export object to module.exports. Note that assigning\nthe desired object to exports will simply rebind the local exports variable,\nwhich is probably not what is desired.
For example, suppose we were making a module called a.js:
const EventEmitter = require('events');\n\nmodule.exports = new EventEmitter();\n\n// Do some work, and after some time emit\n// the 'ready' event from the module itself.\nsetTimeout(() => {\n module.exports.emit('ready');\n}, 1000);\nThen in another file we could do:
\nconst a = require('./a');\na.on('ready', () => {\n console.log('module \"a\" is ready');\n});\nNote that assignment to module.exports must be done immediately. It cannot be\ndone in any callbacks. This does not work:
x.js:
setTimeout(() => {\n module.exports = { a: 'hello' };\n}, 0);\ny.js:
const x = require('./x');\nconsole.log(x.a);\nThe exports variable is available within a module's file-level scope, and is\nassigned the value of module.exports before the module is evaluated.
It allows a shortcut, so that module.exports.f = ... can be written more\nsuccinctly as exports.f = .... However, be aware that like any variable, if a\nnew value is assigned to exports, it is no longer bound to module.exports:
module.exports.hello = true; // Exported from require of module\nexports = { hello: false }; // Not exported, only available in the module\nWhen the module.exports property is being completely replaced by a new\nobject, it is common to also reassign exports:
module.exports = exports = function Constructor() {\n // ... etc.\n};\nTo illustrate the behavior, imagine this hypothetical implementation of\nrequire(), which is quite similar to what is actually done by require():
function require(/* ... */) {\n const module = { exports: {} };\n ((module, exports) => {\n // Module code here. In this example, define a function.\n function someFunc() {}\n exports = someFunc;\n // At this point, exports is no longer a shortcut to module.exports, and\n // this module will still export an empty default object.\n module.exports = someFunc;\n // At this point, the module will now export someFunc, instead of the\n // default object.\n })(module, module.exports);\n return module.exports;\n}\nThe fully resolved filename to the module.
" }, { "textRaw": "`id` {string}", "type": "string", "name": "id", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The identifier for the module. Typically this is the fully resolved\nfilename.
" }, { "textRaw": "`loaded` {boolean}", "type": "boolean", "name": "loaded", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "Whether or not the module is done loading, or is in the process of\nloading.
" }, { "textRaw": "`parent` {module}", "type": "module", "name": "parent", "meta": { "added": [ "v0.1.16" ], "changes": [] }, "desc": "The module that first required this one.
" }, { "textRaw": "`paths` {string[]}", "type": "string[]", "name": "paths", "meta": { "added": [ "v0.4.0" ], "changes": [] }, "desc": "The search paths for the module.
" } ], "methods": [ { "textRaw": "module.require(id)", "type": "method", "name": "require", "meta": { "added": [ "v0.5.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object} `module.exports` from the resolved module", "name": "return", "type": "Object", "desc": "`module.exports` from the resolved module" }, "params": [ { "textRaw": "`id` {string}", "name": "id", "type": "string" } ] } ], "desc": "The module.require method provides a way to load a module as if\nrequire() was called from the original module.
In order to do this, it is necessary to get a reference to the module object.\nSince require() returns the module.exports, and the module is typically\nonly available within a specific module's code, it must be explicitly exported\nin order to be used.
\n\nStability: 2 - Stable
\n
The net module provides an asynchronous network API for creating stream-based\nTCP or IPC servers (net.createServer()) and clients\n(net.createConnection()).
It can be accessed using:
\nconst net = require('net');\nThe net module supports IPC with named pipes on Windows, and UNIX domain\nsockets on other operating systems.
net.connect(), net.createConnection(), server.listen() and\nsocket.connect() take a path parameter to identify IPC endpoints.
On UNIX, the local domain is also known as the UNIX domain. The path is a\nfilesystem pathname. It gets truncated to sizeof(sockaddr_un.sun_path) - 1,\nwhich varies on different operating system between 91 and 107 bytes.\nThe typical values are 107 on Linux and 103 on macOS. The path is\nsubject to the same naming conventions and permissions checks as would be done\non file creation. If the UNIX domain socket (that is visible as a file system\npath) is created and used in conjunction with one of Node.js' API abstractions\nsuch as net.createServer(), it will be unlinked as part of\nserver.close(). On the other hand, if it is created and used outside of\nthese abstractions, the user will need to manually remove it. The same applies\nwhen the path was created by a Node.js API but the program crashes abruptly.\nIn short, a UNIX domain socket once successfully created will be visible in the\nfilesystem, and will persist until unlinked.
On Windows, the local domain is implemented using a named pipe. The path must\nrefer to an entry in \\\\?\\pipe\\ or \\\\.\\pipe\\. Any characters are permitted,\nbut the latter may do some processing of pipe names, such as resolving ..\nsequences. Despite how it might look, the pipe namespace is flat. Pipes will\nnot persist. They are removed when the last reference to them is closed.\nUnlike UNIX domain sockets, Windows will close and remove the pipe when the\nowning process exits.
JavaScript string escaping requires paths to be specified with extra backslash\nescaping such as:
\nnet.createServer().listen(\n path.join('\\\\\\\\?\\\\pipe', process.cwd(), 'myctl'));\nThis class is used to create a TCP or IPC server.
", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "meta": { "added": [ "v0.5.0" ], "changes": [] }, "params": [], "desc": "Emitted when the server closes. Note that if connections exist, this\nevent is not emitted until all connections are ended.
" }, { "textRaw": "Event: 'connection'", "type": "event", "name": "connection", "meta": { "added": [ "v0.1.90" ], "changes": [] }, "params": [ { "textRaw": "{net.Socket} The connection object", "type": "net.Socket", "desc": "The connection object" } ], "desc": "Emitted when a new connection is made. socket is an instance of\nnet.Socket.
Emitted when an error occurs. Unlike net.Socket, the 'close'\nevent will not be emitted directly following this event unless\nserver.close() is manually called. See the example in discussion of\nserver.listen().
Emitted when the server has been bound after calling server.listen().
Returns the bound address, the address family name, and port of the server\nas reported by the operating system if listening on an IP socket\n(useful to find which port was assigned when getting an OS-assigned address):\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }.
For a server listening on a pipe or UNIX domain socket, the name is returned\nas a string.
\nconst server = net.createServer((socket) => {\n socket.end('goodbye\\n');\n}).on('error', (err) => {\n // handle errors here\n throw err;\n});\n\n// grab an arbitrary unused port.\nserver.listen(() => {\n console.log('opened server on', server.address());\n});\nDon't call server.address() until the 'listening' event has been emitted.
Stops the server from accepting new connections and keeps existing\nconnections. This function is asynchronous, the server is finally closed\nwhen all connections are ended and the server emits a 'close' event.\nThe optional callback will be called once the 'close' event occurs. Unlike\nthat event, it will be called with an Error as its only argument if the server\nwas not open when it was closed.
Asynchronously get the number of concurrent connections on the server. Works\nwhen sockets were sent to forks.
\nCallback should take two arguments err and count.
Start a server listening for connections. A net.Server can be a TCP or\nan IPC server depending on what it listens to.
Possible signatures:
\nserver.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback])\nfor IPC serversserver.listen([port[, host[, backlog]]][, callback])\nfor TCP servers\nThis function is asynchronous. When the server starts listening, the\n'listening' event will be emitted. The last parameter callback\nwill be added as a listener for the 'listening' event.
All listen() methods can take a backlog parameter to specify the maximum\nlength of the queue of pending connections. The actual length will be determined\nby the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn\non Linux. The default value of this parameter is 511 (not 512).
All net.Socket are set to SO_REUSEADDR (see socket(7) for\ndetails).
The server.listen() method can be called again if and only if there was an\nerror during the first server.listen() call or server.close() has been\ncalled. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.\nThis happens when another server is already listening on the requested\nport/path/handle. One way to handle this would be to retry\nafter a certain amount of time:
server.on('error', (e) => {\n if (e.code === 'EADDRINUSE') {\n console.log('Address in use, retrying...');\n setTimeout(() => {\n server.close();\n server.listen(PORT, HOST);\n }, 1000);\n }\n});\nStart a server listening for connections on a given handle that has\nalready been bound to a port, a UNIX domain socket, or a Windows named pipe.
The handle object can be either a server, a socket (anything with an\nunderlying _handle member), or an object with an fd member that is a\nvalid file descriptor.
Listening on a file descriptor is not supported on Windows.
" }, { "textRaw": "server.listen(options[, callback])", "type": "method", "name": "listen", "meta": { "added": [ "v0.11.14" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {net.Server}", "name": "return", "type": "net.Server" }, "params": [ { "textRaw": "`options` {Object} Required. Supports the following properties:", "name": "options", "type": "Object", "desc": "Required. Supports the following properties:", "options": [ { "textRaw": "`port` {number}", "name": "port", "type": "number" }, { "textRaw": "`host` {string}", "name": "host", "type": "string" }, { "textRaw": "`path` {string} Will be ignored if `port` is specified. See [Identifying paths for IPC connections][].", "name": "path", "type": "string", "desc": "Will be ignored if `port` is specified. See [Identifying paths for IPC connections][]." }, { "textRaw": "`backlog` {number} Common parameter of [`server.listen()`][] functions.", "name": "backlog", "type": "number", "desc": "Common parameter of [`server.listen()`][] functions." }, { "textRaw": "`exclusive` {boolean} **Default:** `false`", "name": "exclusive", "type": "boolean", "default": "`false`" }, { "textRaw": "`readableAll` {boolean} For IPC servers makes the pipe readable for all users. **Default:** `false`", "name": "readableAll", "type": "boolean", "default": "`false`", "desc": "For IPC servers makes the pipe readable for all users." }, { "textRaw": "`writableAll` {boolean} For IPC servers makes the pipe writable for all users. **Default:** `false`", "name": "writableAll", "type": "boolean", "default": "`false`", "desc": "For IPC servers makes the pipe writable for all users." } ] }, { "textRaw": "`callback` {Function} Common parameter of [`server.listen()`][] functions.", "name": "callback", "type": "Function", "desc": "Common parameter of [`server.listen()`][] functions.", "optional": true } ] } ], "desc": "If port is specified, it behaves the same as\n\nserver.listen([port[, host[, backlog]]][, callback]).\nOtherwise, if path is specified, it behaves the same as\nserver.listen(path[, backlog][, callback]).\nIf none of them is specified, an error will be thrown.
If exclusive is false (default), then cluster workers will use the same\nunderlying handle, allowing connection handling duties to be shared. When\nexclusive is true, the handle is not shared, and attempted port sharing\nresults in an error. An example which listens on an exclusive port is\nshown below.
server.listen({\n host: 'localhost',\n port: 80,\n exclusive: true\n});\nStarting an IPC server as root may cause the server path to be inaccessible for\nunprivileged users. Using readableAll and writableAll will make the server\naccessible for all users.
Start an IPC server listening for connections on the given path.
Start a TCP server listening for connections on the given port and host.
If port is omitted or is 0, the operating system will assign an arbitrary\nunused port, which can be retrieved by using server.address().port\nafter the 'listening' event has been emitted.
If host is omitted, the server will accept connections on the\nunspecified IPv6 address (::) when IPv6 is available, or the\nunspecified IPv4 address (0.0.0.0) otherwise.
In most operating systems, listening to the unspecified IPv6 address (::)\nmay cause the net.Server to also listen on the unspecified IPv4 address\n(0.0.0.0).
Opposite of unref(), calling ref() on a previously unrefed server will\nnot let the program exit if it's the only server left (the default behavior).\nIf the server is refed calling ref() again will have no effect.
Calling unref() on a server will allow the program to exit if this is the only\nactive server in the event system. If the server is already unrefed calling\nunref() again will have no effect.
The number of concurrent connections on the server.
\nThis becomes null when sending a socket to a child with\nchild_process.fork(). To poll forks and get current number of active\nconnections, use asynchronous server.getConnections() instead.
Set this property to reject connections when the server's connection count gets\nhigh.
\nIt is not recommended to use this option once a socket has been sent to a child\nwith child_process.fork().
net.Server is an EventEmitter with the following events:
This class is an abstraction of a TCP socket or a streaming IPC endpoint\n(uses named pipes on Windows, and UNIX domain sockets otherwise). A\nnet.Socket is also a duplex stream, so it can be both readable and\nwritable, and it is also an EventEmitter.
A net.Socket can be created by the user and used directly to interact with\na server. For example, it is returned by net.createConnection(),\nso the user can use it to talk to the server.
It can also be created by Node.js and passed to the user when a connection\nis received. For example, it is passed to the listeners of a\n'connection' event emitted on a net.Server, so the user can use\nit to interact with the client.
Emitted once the socket is fully closed. The argument hadError is a boolean\nwhich says if the socket was closed due to a transmission error.
Emitted when a socket connection is successfully established.\nSee net.createConnection().
Emitted when data is received. The argument data will be a Buffer or\nString. Encoding of data is set by socket.setEncoding().
Note that the data will be lost if there is no listener when a Socket\nemits a 'data' event.
Emitted when the write buffer becomes empty. Can be used to throttle uploads.
\nSee also: the return values of socket.write().
Emitted when the other end of the socket sends a FIN packet, thus ending the\nreadable side of the socket.
\nBy default (allowHalfOpen is false) the socket will send a FIN packet\nback and destroy its file descriptor once it has written out its pending\nwrite queue. However, if allowHalfOpen is set to true, the socket will\nnot automatically end() its writable side, allowing the\nuser to write arbitrary amounts of data. The user must call\nend() explicitly to close the connection (i.e. sending a\nFIN packet back).
Emitted when an error occurs. The 'close' event will be called directly\nfollowing this event.
Emitted after resolving the hostname but before connecting.\nNot applicable to UNIX sockets.
\nerr <Error> | <null> The error object. See dns.lookup().address <string> The IP address.family <string> | <null> The address type. See dns.lookup().host <string> The hostname.Emitted when a socket is ready to be used.
\nTriggered immediately after 'connect'.
Emitted if the socket times out from inactivity. This is only to notify that\nthe socket has been idle. The user must manually close the connection.
\nSee also: socket.setTimeout().
Returns the bound address, the address family name and port of the\nsocket as reported by the operating system:\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
Initiate a connection on a given socket.
\nPossible signatures:
\nsocket.connect(options[, connectListener])socket.connect(path[, connectListener])\nfor IPC connections.socket.connect(port[, host][, connectListener])\nfor TCP connections.This function is asynchronous. When the connection is established, the\n'connect' event will be emitted. If there is a problem connecting,\ninstead of a 'connect' event, an 'error' event will be emitted with\nthe error passed to the 'error' listener.\nThe last parameter connectListener, if supplied, will be added as a listener\nfor the 'connect' event once.
Initiate a connection on a given socket. Normally this method is not needed,\nthe socket should be created and opened with net.createConnection(). Use\nthis only when implementing a custom Socket.
For TCP connections, available options are:
port <number> Required. Port the socket should connect to.host <string> Host the socket should connect to. Default: 'localhost'.localAddress <string> Local address the socket should connect from.localPort <number> Local port the socket should connect from.family <number>: Version of IP stack, can be either 4 or 6.\nDefault: 4.hints <number> Optional dns.lookup() hints.lookup <Function> Custom lookup function. Default: dns.lookup().For IPC connections, available options are:
path <string> Required. Path the client should connect to.\nSee Identifying paths for IPC connections. If provided, the TCP-specific\noptions above are ignored.Initiate an IPC connection on the given socket.
\nAlias to\nsocket.connect(options[, connectListener])\ncalled with { path: path } as options.
Initiate a TCP connection on the given socket.
\nAlias to\nsocket.connect(options[, connectListener])\ncalled with {port: port, host: host} as options.
Ensures that no more I/O activity happens on this socket. Only necessary in\ncase of errors (parse error or so).
\nIf exception is specified, an 'error' event will be emitted and any\nlisteners for that event will receive exception as an argument.
Half-closes the socket. i.e., it sends a FIN packet. It is possible the\nserver will still send some data.
\nIf data is specified, it is equivalent to calling\nsocket.write(data, encoding) followed by socket.end().
Pauses the reading of data. That is, 'data' events will not be emitted.\nUseful to throttle back an upload.
Opposite of unref(), calling ref() on a previously unrefed socket will\nnot let the program exit if it's the only socket left (the default behavior).\nIf the socket is refed calling ref again will have no effect.
Resumes reading after a call to socket.pause().
Set the encoding for the socket as a Readable Stream. See\nreadable.setEncoding() for more information.
Enable/disable keep-alive functionality, and optionally set the initial\ndelay before the first keepalive probe is sent on an idle socket.
\nSet initialDelay (in milliseconds) to set the delay between the last\ndata packet received and the first keepalive probe. Setting 0 for\ninitialDelay will leave the value unchanged from the default\n(or previous) setting.
Disables the Nagle algorithm. By default TCP connections use the Nagle\nalgorithm, they buffer data before sending it off. Setting true for\nnoDelay will immediately fire off data each time socket.write() is called.
Sets the socket to timeout after timeout milliseconds of inactivity on\nthe socket. By default net.Socket do not have a timeout.
When an idle timeout is triggered the socket will receive a 'timeout'\nevent but the connection will not be severed. The user must manually call\nsocket.end() or socket.destroy() to end the connection.
socket.setTimeout(3000);\nsocket.on('timeout', () => {\n console.log('socket timeout');\n socket.end();\n});\nIf timeout is 0, then the existing idle timeout is disabled.
The optional callback parameter will be added as a one-time listener for the\n'timeout' event.
Calling unref() on a socket will allow the program to exit if this is the only\nactive socket in the event system. If the socket is already unrefed calling\nunref() again will have no effect.
Sends data on the socket. The second parameter specifies the encoding in the\ncase of a string — it defaults to UTF8 encoding.
\nReturns true if the entire data was flushed successfully to the kernel\nbuffer. Returns false if all or part of the data was queued in user memory.\n'drain' will be emitted when the buffer is again free.
The optional callback parameter will be executed when the data is finally\nwritten out - this may not be immediately.
See Writable stream write() method for more\ninformation.
net.Socket has the property that socket.write() always works. This is to\nhelp users get up and running quickly. The computer cannot always keep up\nwith the amount of data that is written to a socket - the network connection\nsimply might be too slow. Node.js will internally queue up the data written to a\nsocket and send it out over the wire when it is possible. (Internally it is\npolling on the socket's file descriptor for being writable).
The consequence of this internal buffering is that memory may grow. This\nproperty shows the number of characters currently buffered to be written.\n(Number of characters is approximately equal to the number of bytes to be\nwritten, but the buffer may contain strings, and the strings are lazily\nencoded, so the exact number of bytes is not known.)
\nUsers who experience large or growing bufferSize should attempt to\n\"throttle\" the data flows in their program with\nsocket.pause() and socket.resume().
The amount of received bytes.
" }, { "textRaw": "socket.bytesWritten", "name": "bytesWritten", "meta": { "added": [ "v0.5.3" ], "changes": [] }, "desc": "The amount of bytes sent.
" }, { "textRaw": "socket.connecting", "name": "connecting", "meta": { "added": [ "v6.1.0" ], "changes": [] }, "desc": "If true,\nsocket.connect(options[, connectListener]) was\ncalled and has not yet finished. It will stay true until the socket becomes\nconnected, then it is set to false and the 'connect' event is emitted. Note\nthat the\nsocket.connect(options[, connectListener])\ncallback is a listener for the 'connect' event.
The string representation of the local IP address the remote client is\nconnecting on. For example, in a server listening on '0.0.0.0', if a client\nconnects on '192.168.1.1', the value of socket.localAddress would be\n'192.168.1.1'.
The numeric representation of the local port. For example, 80 or 21.
This is true if the socket is not connected yet, either because .connect()\nhas not yet been called or because it is still in the process of connecting\n(see socket.connecting).
The string representation of the remote IP address. For example,\n'74.125.127.100' or '2001:4860:a005::68'. Value may be undefined if\nthe socket is destroyed (for example, if the client disconnected).
The string representation of the remote IP family. 'IPv4' or 'IPv6'.
The numeric representation of the remote port. For example, 80 or 21.
Creates a new socket object.
\nThe newly created socket can be either a TCP socket or a streaming IPC\nendpoint, depending on what it connect() to.
Aliases to\nnet.createConnection().
Possible signatures:
\nnet.connect(options[, connectListener])net.connect(path[, connectListener]) for IPC\nconnections.net.connect(port[, host][, connectListener])\nfor TCP connections.Alias to\nnet.createConnection(options[, connectListener]).
Alias to\nnet.createConnection(path[, connectListener]).
Alias to\nnet.createConnection(port[, host][, connectListener]).
A factory function, which creates a new net.Socket,\nimmediately initiates connection with socket.connect(),\nthen returns the net.Socket that starts the connection.
When the connection is established, a 'connect' event will be emitted\non the returned socket. The last parameter connectListener, if supplied,\nwill be added as a listener for the 'connect' event once.
Possible signatures:
\nnet.createConnection(options[, connectListener])net.createConnection(path[, connectListener])\nfor IPC connections.net.createConnection(port[, host][, connectListener])\nfor TCP connections.The net.connect() function is an alias to this function.
For available options, see\nnew net.Socket([options])\nand socket.connect(options[, connectListener]).
Additional options:
\ntimeout <number> If set, will be used to call\nsocket.setTimeout(timeout) after the socket is created, but before\nit starts the connection.Following is an example of a client of the echo server described\nin the net.createServer() section:
const net = require('net');\nconst client = net.createConnection({ port: 8124 }, () => {\n // 'connect' listener\n console.log('connected to server!');\n client.write('world!\\r\\n');\n});\nclient.on('data', (data) => {\n console.log(data.toString());\n client.end();\n});\nclient.on('end', () => {\n console.log('disconnected from server');\n});\nTo connect on the socket /tmp/echo.sock the second line would just be\nchanged to:
const client = net.createConnection({ path: '/tmp/echo.sock' });\nInitiates an IPC connection.
\nThis function creates a new net.Socket with all options set to default,\nimmediately initiates connection with\nsocket.connect(path[, connectListener]),\nthen returns the net.Socket that starts the connection.
Initiates a TCP connection.
\nThis function creates a new net.Socket with all options set to default,\nimmediately initiates connection with\nsocket.connect(port[, host][, connectListener]),\nthen returns the net.Socket that starts the connection.
Creates a new TCP or IPC server.
\nIf allowHalfOpen is set to true, when the other end of the socket\nsends a FIN packet, the server will only send a FIN packet back when\nsocket.end() is explicitly called, until then the connection is\nhalf-closed (non-readable but still writable). See 'end' event\nand RFC 1122 (section 4.2.2.13) for more information.
If pauseOnConnect is set to true, then the socket associated with each\nincoming connection will be paused, and no data will be read from its handle.\nThis allows connections to be passed between processes without any data being\nread by the original process. To begin reading data from a paused socket, call\nsocket.resume().
The server can be a TCP server or an IPC server, depending on what it\nlisten() to.
Here is an example of an TCP echo server which listens for connections\non port 8124:
\nconst net = require('net');\nconst server = net.createServer((c) => {\n // 'connection' listener\n console.log('client connected');\n c.on('end', () => {\n console.log('client disconnected');\n });\n c.write('hello\\r\\n');\n c.pipe(c);\n});\nserver.on('error', (err) => {\n throw err;\n});\nserver.listen(8124, () => {\n console.log('server bound');\n});\nTest this by using telnet:
$ telnet localhost 8124\nTo listen on the socket /tmp/echo.sock the third line from the last would\njust be changed to:
server.listen('/tmp/echo.sock', () => {\n console.log('server bound');\n});\nUse nc to connect to a UNIX domain socket server:
$ nc -U /tmp/echo.sock\nTests if input is an IP address. Returns 0 for invalid strings,\nreturns 4 for IP version 4 addresses, and returns 6 for IP version 6\naddresses.
Returns true if input is a version 4 IP address, otherwise returns false.
Returns true if input is a version 6 IP address, otherwise returns false.
The os module provides a number of operating system-related utility methods.\nIt can be accessed using:
const os = require('os');\nA string constant defining the operating system-specific end-of-line marker:
\n\\n on POSIX\\r\\n on WindowsReturns an object containing commonly used operating system specific constants\nfor error codes, process signals, and so on. The specific constants currently\ndefined are described in OS Constants.
" } ], "methods": [ { "textRaw": "os.arch()", "type": "method", "name": "arch", "meta": { "added": [ "v0.5.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {string}", "name": "return", "type": "string" }, "params": [] } ], "desc": "The os.arch() method returns a string identifying the operating system CPU\narchitecture for which the Node.js binary was compiled.
The current possible values are: 'arm', 'arm64', 'ia32', 'mips',\n'mipsel', 'ppc', 'ppc64', 's390', 's390x', 'x32', and 'x64'.
Equivalent to process.arch.
The os.cpus() method returns an array of objects containing information about\neach logical CPU core.
The properties included on each object include:
\nmodel <string>speed <number> (in MHz)times <Object>
user <number> The number of milliseconds the CPU has spent in user mode.nice <number> The number of milliseconds the CPU has spent in nice mode.sys <number> The number of milliseconds the CPU has spent in sys mode.idle <number> The number of milliseconds the CPU has spent in idle mode.irq <number> The number of milliseconds the CPU has spent in irq mode.[\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 252020,\n nice: 0,\n sys: 30340,\n idle: 1070356870,\n irq: 0\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 306960,\n nice: 0,\n sys: 26980,\n idle: 1071569080,\n irq: 0\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 248450,\n nice: 0,\n sys: 21750,\n idle: 1070919370,\n irq: 0\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 256880,\n nice: 0,\n sys: 19430,\n idle: 1070905480,\n irq: 20\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 511580,\n nice: 20,\n sys: 40900,\n idle: 1070842510,\n irq: 0\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 291660,\n nice: 0,\n sys: 34360,\n idle: 1070888000,\n irq: 10\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 308260,\n nice: 0,\n sys: 55410,\n idle: 1071129970,\n irq: 880\n }\n },\n {\n model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times: {\n user: 266450,\n nice: 1480,\n sys: 34920,\n idle: 1072572010,\n irq: 30\n }\n }\n]\nBecause nice values are UNIX-specific, on Windows the nice values of all\nprocessors are always 0.
The os.endianness() method returns a string identifying the endianness of the\nCPU for which the Node.js binary was compiled.
Possible values are:
\n'BE' for big endian'LE' for little endian.The os.freemem() method returns the amount of free system memory in bytes as\nan integer.
The os.getPriority() method returns the scheduling priority for the process\nspecified by pid. If pid is not provided, or is 0, the priority of the\ncurrent process is returned.
The os.homedir() method returns the home directory of the current user as a\nstring.
The os.hostname() method returns the hostname of the operating system as a\nstring.
The os.loadavg() method returns an array containing the 1, 5, and 15 minute\nload averages.
The load average is a measure of system activity, calculated by the operating\nsystem and expressed as a fractional number. As a rule of thumb, the load\naverage should ideally be less than the number of logical CPUs in the system.
\nThe load average is a UNIX-specific concept with no real equivalent on\nWindows platforms. On Windows, the return value is always [0, 0, 0].
The os.networkInterfaces() method returns an object containing only network\ninterfaces that have been assigned a network address.
Each key on the returned object identifies a network interface. The associated\nvalue is an array of objects that each describe an assigned network address.
\nThe properties available on the assigned network address object include:
\naddress <string> The assigned IPv4 or IPv6 addressnetmask <string> The IPv4 or IPv6 network maskfamily <string> Either IPv4 or IPv6mac <string> The MAC address of the network interfaceinternal <boolean> true if the network interface is a loopback or\nsimilar interface that is not remotely accessible; otherwise falsescopeid <number> The numeric IPv6 scope ID (only specified when family\nis IPv6)cidr <string> The assigned IPv4 or IPv6 address with the routing prefix\nin CIDR notation. If the netmask is invalid, this property is set\nto null.{\n lo: [\n {\n address: '127.0.0.1',\n netmask: '255.0.0.0',\n family: 'IPv4',\n mac: '00:00:00:00:00:00',\n internal: true,\n cidr: '127.0.0.1/8'\n },\n {\n address: '::1',\n netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',\n family: 'IPv6',\n mac: '00:00:00:00:00:00',\n scopeid: 0,\n internal: true,\n cidr: '::1/128'\n }\n ],\n eth0: [\n {\n address: '192.168.1.108',\n netmask: '255.255.255.0',\n family: 'IPv4',\n mac: '01:02:03:0a:0b:0c',\n internal: false,\n cidr: '192.168.1.108/24'\n },\n {\n address: 'fe80::a00:27ff:fe4e:66a1',\n netmask: 'ffff:ffff:ffff:ffff::',\n family: 'IPv6',\n mac: '01:02:03:0a:0b:0c',\n scopeid: 1,\n internal: false,\n cidr: 'fe80::a00:27ff:fe4e:66a1/64'\n }\n ]\n}\nThe os.platform() method returns a string identifying the operating system\nplatform as set during compile time of Node.js.
Currently possible values are:
\n'aix''darwin''freebsd''linux''openbsd''sunos''win32'Equivalent to process.platform.
The value 'android' may also be returned if the Node.js is built on the\nAndroid operating system. However, Android support in Node.js is considered\nto be experimental at this time.
The os.release() method returns a string identifying the operating system\nrelease.
On POSIX systems, the operating system release is determined by calling\nuname(3). On Windows, GetVersionExW() is used. Please see\nhttps://en.wikipedia.org/wiki/Uname#Examples for more information.
The os.setPriority() method attempts to set the scheduling priority for the\nprocess specified by pid. If pid is not provided, or is 0, the priority\nof the current process is used.
The priority input must be an integer between -20 (high priority) and 19\n(low priority). Due to differences between Unix priority levels and Windows\npriority classes, priority is mapped to one of six priority constants in\nos.constants.priority. When retrieving a process priority level, this range\nmapping may cause the return value to be slightly different on Windows. To avoid\nconfusion, it is recommended to set priority to one of the priority constants.
On Windows setting priority to PRIORITY_HIGHEST requires elevated user,\notherwise the set priority will be silently reduced to PRIORITY_HIGH.
The os.tmpdir() method returns a string specifying the operating system's\ndefault directory for temporary files.
The os.totalmem() method returns the total amount of system memory in bytes\nas an integer.
The os.type() method returns a string identifying the operating system name\nas returned by uname(3). For example, 'Linux' on Linux, 'Darwin' on\nmacOS, and 'Windows_NT' on Windows.
Please see https://en.wikipedia.org/wiki/Uname#Examples for additional\ninformation about the output of running uname(3) on various operating\nsystems.
The os.uptime() method returns the system uptime in number of seconds.
The os.userInfo() method returns information about the currently effective\nuser — on POSIX platforms, this is typically a subset of the password file. The\nreturned object includes the username, uid, gid, shell, and homedir.\nOn Windows, the uid and gid fields are -1, and shell is null.
The value of homedir returned by os.userInfo() is provided by the operating\nsystem. This differs from the result of os.homedir(), which queries several\nenvironment variables for the home directory before falling back to the\noperating system response.
The following constants are exported by os.constants.
Not all constants will be available on every operating system.
", "modules": [ { "textRaw": "Signal Constants", "name": "signal_constants", "meta": { "changes": [ { "version": "v5.11.0", "pr-url": "https://github.com/nodejs/node/pull/6093", "description": "Added support for `SIGINFO`." } ] }, "desc": "The following signal constants are exported by os.constants.signals:
| Constant | \nDescription | \n
|---|---|
SIGHUP | \n Sent to indicate when a controlling terminal is closed or a parent\n process exits. | \n
SIGINT | \n Sent to indicate when a user wishes to interrupt a process\n ((Ctrl+C)). | \n
SIGQUIT | \n Sent to indicate when a user wishes to terminate a process and perform a\n core dump. | \n
SIGILL | \n Sent to a process to notify that it has attempted to perform an illegal,\n malformed, unknown, or privileged instruction. | \n
SIGTRAP | \n Sent to a process when an exception has occurred. | \n
SIGABRT | \n Sent to a process to request that it abort. | \n
SIGIOT | \n Synonym for SIGABRT | \n
SIGBUS | \n Sent to a process to notify that it has caused a bus error. | \n
SIGFPE | \n Sent to a process to notify that it has performed an illegal arithmetic\n operation. | \n
SIGKILL | \n Sent to a process to terminate it immediately. | \n
SIGUSR1 SIGUSR2 | \n Sent to a process to identify user-defined conditions. | \n
SIGSEGV | \n Sent to a process to notify of a segmentation fault. | \n
SIGPIPE | \n Sent to a process when it has attempted to write to a disconnected\n pipe. | \n
SIGALRM | \n Sent to a process when a system timer elapses. | \n
SIGTERM | \n Sent to a process to request termination. | \n
SIGCHLD | \n Sent to a process when a child process terminates. | \n
SIGSTKFLT | \n Sent to a process to indicate a stack fault on a coprocessor. | \n
SIGCONT | \n Sent to instruct the operating system to continue a paused process. | \n
SIGSTOP | \n Sent to instruct the operating system to halt a process. | \n
SIGTSTP | \n Sent to a process to request it to stop. | \n
SIGBREAK | \n Sent to indicate when a user wishes to interrupt a process. | \n
SIGTTIN | \n Sent to a process when it reads from the TTY while in the\n background. | \n
SIGTTOU | \n Sent to a process when it writes to the TTY while in the\n background. | \n
SIGURG | \n Sent to a process when a socket has urgent data to read. | \n
SIGXCPU | \n Sent to a process when it has exceeded its limit on CPU usage. | \n
SIGXFSZ | \n Sent to a process when it grows a file larger than the maximum\n allowed. | \n
SIGVTALRM | \n Sent to a process when a virtual timer has elapsed. | \n
SIGPROF | \n Sent to a process when a system timer has elapsed. | \n
SIGWINCH | \n Sent to a process when the controlling terminal has changed its\n size. | \n
SIGIO | \n Sent to a process when I/O is available. | \n
SIGPOLL | \n Synonym for SIGIO | \n
SIGLOST | \n Sent to a process when a file lock has been lost. | \n
SIGPWR | \n Sent to a process to notify of a power failure. | \n
SIGINFO | \n Synonym for SIGPWR | \n
SIGSYS | \n Sent to a process to notify of a bad argument. | \n
SIGUNUSED | \n Synonym for SIGSYS | \n
The following error constants are exported by os.constants.errno:
| Constant | \nDescription | \n
|---|---|
E2BIG | \n Indicates that the list of arguments is longer than expected. | \n
EACCES | \n Indicates that the operation did not have sufficient permissions. | \n
EADDRINUSE | \n Indicates that the network address is already in use. | \n
EADDRNOTAVAIL | \n Indicates that the network address is currently unavailable for\n use. | \n
EAFNOSUPPORT | \n Indicates that the network address family is not supported. | \n
EAGAIN | \n Indicates that there is currently no data available and to try the\n operation again later. | \n
EALREADY | \n Indicates that the socket already has a pending connection in\n progress. | \n
EBADF | \n Indicates that a file descriptor is not valid. | \n
EBADMSG | \n Indicates an invalid data message. | \n
EBUSY | \n Indicates that a device or resource is busy. | \n
ECANCELED | \n Indicates that an operation was canceled. | \n
ECHILD | \n Indicates that there are no child processes. | \n
ECONNABORTED | \n Indicates that the network connection has been aborted. | \n
ECONNREFUSED | \n Indicates that the network connection has been refused. | \n
ECONNRESET | \n Indicates that the network connection has been reset. | \n
EDEADLK | \n Indicates that a resource deadlock has been avoided. | \n
EDESTADDRREQ | \n Indicates that a destination address is required. | \n
EDOM | \n Indicates that an argument is out of the domain of the function. | \n
EDQUOT | \n Indicates that the disk quota has been exceeded. | \n
EEXIST | \n Indicates that the file already exists. | \n
EFAULT | \n Indicates an invalid pointer address. | \n
EFBIG | \n Indicates that the file is too large. | \n
EHOSTUNREACH | \n Indicates that the host is unreachable. | \n
EIDRM | \n Indicates that the identifier has been removed. | \n
EILSEQ | \n Indicates an illegal byte sequence. | \n
EINPROGRESS | \n Indicates that an operation is already in progress. | \n
EINTR | \n Indicates that a function call was interrupted. | \n
EINVAL | \n Indicates that an invalid argument was provided. | \n
EIO | \n Indicates an otherwise unspecified I/O error. | \n
EISCONN | \n Indicates that the socket is connected. | \n
EISDIR | \n Indicates that the path is a directory. | \n
ELOOP | \n Indicates too many levels of symbolic links in a path. | \n
EMFILE | \n Indicates that there are too many open files. | \n
EMLINK | \n Indicates that there are too many hard links to a file. | \n
EMSGSIZE | \n Indicates that the provided message is too long. | \n
EMULTIHOP | \n Indicates that a multihop was attempted. | \n
ENAMETOOLONG | \n Indicates that the filename is too long. | \n
ENETDOWN | \n Indicates that the network is down. | \n
ENETRESET | \n Indicates that the connection has been aborted by the network. | \n
ENETUNREACH | \n Indicates that the network is unreachable. | \n
ENFILE | \n Indicates too many open files in the system. | \n
ENOBUFS | \n Indicates that no buffer space is available. | \n
ENODATA | \n Indicates that no message is available on the stream head read\n queue. | \n
ENODEV | \n Indicates that there is no such device. | \n
ENOENT | \n Indicates that there is no such file or directory. | \n
ENOEXEC | \n Indicates an exec format error. | \n
ENOLCK | \n Indicates that there are no locks available. | \n
ENOLINK | \n Indications that a link has been severed. | \n
ENOMEM | \n Indicates that there is not enough space. | \n
ENOMSG | \n Indicates that there is no message of the desired type. | \n
ENOPROTOOPT | \n Indicates that a given protocol is not available. | \n
ENOSPC | \n Indicates that there is no space available on the device. | \n
ENOSR | \n Indicates that there are no stream resources available. | \n
ENOSTR | \n Indicates that a given resource is not a stream. | \n
ENOSYS | \n Indicates that a function has not been implemented. | \n
ENOTCONN | \n Indicates that the socket is not connected. | \n
ENOTDIR | \n Indicates that the path is not a directory. | \n
ENOTEMPTY | \n Indicates that the directory is not empty. | \n
ENOTSOCK | \n Indicates that the given item is not a socket. | \n
ENOTSUP | \n Indicates that a given operation is not supported. | \n
ENOTTY | \n Indicates an inappropriate I/O control operation. | \n
ENXIO | \n Indicates no such device or address. | \n
EOPNOTSUPP | \n Indicates that an operation is not supported on the socket. Note that\n while ENOTSUP and EOPNOTSUPP have the same value\n on Linux, according to POSIX.1 these error values should be distinct.) | \n
EOVERFLOW | \n Indicates that a value is too large to be stored in a given data\n type. | \n
EPERM | \n Indicates that the operation is not permitted. | \n
EPIPE | \n Indicates a broken pipe. | \n
EPROTO | \n Indicates a protocol error. | \n
EPROTONOSUPPORT | \n Indicates that a protocol is not supported. | \n
EPROTOTYPE | \n Indicates the wrong type of protocol for a socket. | \n
ERANGE | \n Indicates that the results are too large. | \n
EROFS | \n Indicates that the file system is read only. | \n
ESPIPE | \n Indicates an invalid seek operation. | \n
ESRCH | \n Indicates that there is no such process. | \n
ESTALE | \n Indicates that the file handle is stale. | \n
ETIME | \n Indicates an expired timer. | \n
ETIMEDOUT | \n Indicates that the connection timed out. | \n
ETXTBSY | \n Indicates that a text file is busy. | \n
EWOULDBLOCK | \n Indicates that the operation would block. | \n
EXDEV | \n Indicates an improper link.\n |
The following error codes are specific to the Windows operating system:
\n| Constant | \nDescription | \n
|---|---|
WSAEINTR | \n Indicates an interrupted function call. | \n
WSAEBADF | \n Indicates an invalid file handle. | \n
WSAEACCES | \n Indicates insufficient permissions to complete the operation. | \n
WSAEFAULT | \n Indicates an invalid pointer address. | \n
WSAEINVAL | \n Indicates that an invalid argument was passed. | \n
WSAEMFILE | \n Indicates that there are too many open files. | \n
WSAEWOULDBLOCK | \n Indicates that a resource is temporarily unavailable. | \n
WSAEINPROGRESS | \n Indicates that an operation is currently in progress. | \n
WSAEALREADY | \n Indicates that an operation is already in progress. | \n
WSAENOTSOCK | \n Indicates that the resource is not a socket. | \n
WSAEDESTADDRREQ | \n Indicates that a destination address is required. | \n
WSAEMSGSIZE | \n Indicates that the message size is too long. | \n
WSAEPROTOTYPE | \n Indicates the wrong protocol type for the socket. | \n
WSAENOPROTOOPT | \n Indicates a bad protocol option. | \n
WSAEPROTONOSUPPORT | \n Indicates that the protocol is not supported. | \n
WSAESOCKTNOSUPPORT | \n Indicates that the socket type is not supported. | \n
WSAEOPNOTSUPP | \n Indicates that the operation is not supported. | \n
WSAEPFNOSUPPORT | \n Indicates that the protocol family is not supported. | \n
WSAEAFNOSUPPORT | \n Indicates that the address family is not supported. | \n
WSAEADDRINUSE | \n Indicates that the network address is already in use. | \n
WSAEADDRNOTAVAIL | \n Indicates that the network address is not available. | \n
WSAENETDOWN | \n Indicates that the network is down. | \n
WSAENETUNREACH | \n Indicates that the network is unreachable. | \n
WSAENETRESET | \n Indicates that the network connection has been reset. | \n
WSAECONNABORTED | \n Indicates that the connection has been aborted. | \n
WSAECONNRESET | \n Indicates that the connection has been reset by the peer. | \n
WSAENOBUFS | \n Indicates that there is no buffer space available. | \n
WSAEISCONN | \n Indicates that the socket is already connected. | \n
WSAENOTCONN | \n Indicates that the socket is not connected. | \n
WSAESHUTDOWN | \n Indicates that data cannot be sent after the socket has been\n shutdown. | \n
WSAETOOMANYREFS | \n Indicates that there are too many references. | \n
WSAETIMEDOUT | \n Indicates that the connection has timed out. | \n
WSAECONNREFUSED | \n Indicates that the connection has been refused. | \n
WSAELOOP | \n Indicates that a name cannot be translated. | \n
WSAENAMETOOLONG | \n Indicates that a name was too long. | \n
WSAEHOSTDOWN | \n Indicates that a network host is down. | \n
WSAEHOSTUNREACH | \n Indicates that there is no route to a network host. | \n
WSAENOTEMPTY | \n Indicates that the directory is not empty. | \n
WSAEPROCLIM | \n Indicates that there are too many processes. | \n
WSAEUSERS | \n Indicates that the user quota has been exceeded. | \n
WSAEDQUOT | \n Indicates that the disk quota has been exceeded. | \n
WSAESTALE | \n Indicates a stale file handle reference. | \n
WSAEREMOTE | \n Indicates that the item is remote. | \n
WSASYSNOTREADY | \n Indicates that the network subsystem is not ready. | \n
WSAVERNOTSUPPORTED | \n Indicates that the winsock.dll version is out of\n range. | \n
WSANOTINITIALISED | \n Indicates that successful WSAStartup has not yet been performed. | \n
WSAEDISCON | \n Indicates that a graceful shutdown is in progress. | \n
WSAENOMORE | \n Indicates that there are no more results. | \n
WSAECANCELLED | \n Indicates that an operation has been canceled. | \n
WSAEINVALIDPROCTABLE | \n Indicates that the procedure call table is invalid. | \n
WSAEINVALIDPROVIDER | \n Indicates an invalid service provider. | \n
WSAEPROVIDERFAILEDINIT | \n Indicates that the service provider failed to initialized. | \n
WSASYSCALLFAILURE | \n Indicates a system call failure. | \n
WSASERVICE_NOT_FOUND | \n Indicates that a service was not found. | \n
WSATYPE_NOT_FOUND | \n Indicates that a class type was not found. | \n
WSA_E_NO_MORE | \n Indicates that there are no more results. | \n
WSA_E_CANCELLED | \n Indicates that the call was canceled. | \n
WSAEREFUSED | \n Indicates that a database query was refused. | \n
If available on the operating system, the following constants\nare exported in os.constants.dlopen. See dlopen(3) for detailed\ninformation.
| Constant | \nDescription | \n
|---|---|
RTLD_LAZY | \n Perform lazy binding. Node.js sets this flag by default. | \n
RTLD_NOW | \n Resolve all undefined symbols in the library before dlopen(3)\n returns. | \n
RTLD_GLOBAL | \n Symbols defined by the library will be made available for symbol\n resolution of subsequently loaded libraries. | \n
RTLD_LOCAL | \n The converse of RTLD_GLOBAL. This is the default behavior\n if neither flag is specified. | \n
RTLD_DEEPBIND | \n Make a self-contained library use its own symbols in preference to\n symbols from previously loaded libraries. | \n
The following process scheduling constants are exported by\nos.constants.priority:
| Constant | \nDescription | \n
|---|---|
PRIORITY_LOW | \n The lowest process scheduling priority. This corresponds to\n IDLE_PRIORITY_CLASS on Windows, and a nice value of\n 19 on all other platforms. | \n
PRIORITY_BELOW_NORMAL | \n The process scheduling priority above PRIORITY_LOW and\n below PRIORITY_NORMAL. This corresponds to\n BELOW_NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n 10 on all other platforms. | \n
PRIORITY_NORMAL | \n The default process scheduling priority. This corresponds to\n NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n 0 on all other platforms. | \n
PRIORITY_ABOVE_NORMAL | \n The process scheduling priority above PRIORITY_NORMAL and\n below PRIORITY_HIGH. This corresponds to\n ABOVE_NORMAL_PRIORITY_CLASS on Windows, and a nice value of\n -7 on all other platforms. | \n
PRIORITY_HIGH | \n The process scheduling priority above PRIORITY_ABOVE_NORMAL\n and below PRIORITY_HIGHEST. This corresponds to\n HIGH_PRIORITY_CLASS on Windows, and a nice value of\n -14 on all other platforms. | \n
PRIORITY_HIGHEST | \n The highest process scheduling priority. This corresponds to\n REALTIME_PRIORITY_CLASS on Windows, and a nice value of\n -20 on all other platforms. | \n
| Constant | \nDescription | \n
|---|---|
UV_UDP_REUSEADDR | \n \n |
The path module provides utilities for working with file and directory paths.\nIt can be accessed using:
const path = require('path');\nThe default operation of the path module varies based on the operating system\non which a Node.js application is running. Specifically, when running on a\nWindows operating system, the path module will assume that Windows-style\npaths are being used.
So using path.basename() might yield different results on POSIX and Windows:
On POSIX:
\npath.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'C:\\\\temp\\\\myfile.html'\nOn Windows:
\npath.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'myfile.html'\nTo achieve consistent results when working with Windows file paths on any\noperating system, use path.win32:
On POSIX and Windows:
\npath.win32.basename('C:\\\\temp\\\\myfile.html');\n// Returns: 'myfile.html'\nTo achieve consistent results when working with POSIX file paths on any\noperating system, use path.posix:
On POSIX and Windows:
\npath.posix.basename('/tmp/myfile.html');\n// Returns: 'myfile.html'\nOn Windows Node.js follows the concept of per-drive working directory.\nThis behavior can be observed when using a drive path without a backslash. For\nexample, path.resolve('c:\\\\') can potentially return a different result than\npath.resolve('c:'). For more information, see\nthis MSDN page.
The path.basename() methods returns the last portion of a path, similar to\nthe Unix basename command. Trailing directory separators are ignored, see\npath.sep.
path.basename('/foo/bar/baz/asdf/quux.html');\n// Returns: 'quux.html'\n\npath.basename('/foo/bar/baz/asdf/quux.html', '.html');\n// Returns: 'quux'\nA TypeError is thrown if path is not a string or if ext is given\nand is not a string.
The path.dirname() method returns the directory name of a path, similar to\nthe Unix dirname command. Trailing directory separators are ignored, see\npath.sep.
path.dirname('/foo/bar/baz/asdf/quux');\n// Returns: '/foo/bar/baz/asdf'\nA TypeError is thrown if path is not a string.
The path.extname() method returns the extension of the path, from the last\noccurrence of the . (period) character to end of string in the last portion of\nthe path. If there is no . in the last portion of the path, or if the\nfirst character of the basename of path (see path.basename()) is ., then\nan empty string is returned.
path.extname('index.html');\n// Returns: '.html'\n\npath.extname('index.coffee.md');\n// Returns: '.md'\n\npath.extname('index.');\n// Returns: '.'\n\npath.extname('index');\n// Returns: ''\n\npath.extname('.index');\n// Returns: ''\nA TypeError is thrown if path is not a string.
The path.format() method returns a path string from an object. This is the\nopposite of path.parse().
When providing properties to the pathObject remember that there are\ncombinations where one property has priority over another:
pathObject.root is ignored if pathObject.dir is providedpathObject.ext and pathObject.name are ignored if pathObject.base existsFor example, on POSIX:
\n// If `dir`, `root` and `base` are provided,\n// `${dir}${path.sep}${base}`\n// will be returned. `root` is ignored.\npath.format({\n root: '/ignored',\n dir: '/home/user/dir',\n base: 'file.txt'\n});\n// Returns: '/home/user/dir/file.txt'\n\n// `root` will be used if `dir` is not specified.\n// If only `root` is provided or `dir` is equal to `root` then the\n// platform separator will not be included. `ext` will be ignored.\npath.format({\n root: '/',\n base: 'file.txt',\n ext: 'ignored'\n});\n// Returns: '/file.txt'\n\n// `name` + `ext` will be used if `base` is not specified.\npath.format({\n root: '/',\n name: 'file',\n ext: '.txt'\n});\n// Returns: '/file.txt'\nOn Windows:
\npath.format({\n dir: 'C:\\\\path\\\\dir',\n base: 'file.txt'\n});\n// Returns: 'C:\\\\path\\\\dir\\\\file.txt'\nThe path.isAbsolute() method determines if path is an absolute path.
If the given path is a zero-length string, false will be returned.
For example, on POSIX:
\npath.isAbsolute('/foo/bar'); // true\npath.isAbsolute('/baz/..'); // true\npath.isAbsolute('qux/'); // false\npath.isAbsolute('.'); // false\nOn Windows:
\npath.isAbsolute('//server'); // true\npath.isAbsolute('\\\\\\\\server'); // true\npath.isAbsolute('C:/foo/..'); // true\npath.isAbsolute('C:\\\\foo\\\\..'); // true\npath.isAbsolute('bar\\\\baz'); // false\npath.isAbsolute('bar/baz'); // false\npath.isAbsolute('.'); // false\nA TypeError is thrown if path is not a string.
The path.join() method joins all given path segments together using the\nplatform-specific separator as a delimiter, then normalizes the resulting path.
Zero-length path segments are ignored. If the joined path string is a\nzero-length string then '.' will be returned, representing the current\nworking directory.
path.join('/foo', 'bar', 'baz/asdf', 'quux', '..');\n// Returns: '/foo/bar/baz/asdf'\n\npath.join('foo', {}, 'bar');\n// throws 'TypeError: Path must be a string. Received {}'\nA TypeError is thrown if any of the path segments is not a string.
The path.normalize() method normalizes the given path, resolving '..' and\n'.' segments.
When multiple, sequential path segment separation characters are found (e.g.\n/ on POSIX and either \\ or / on Windows), they are replaced by a single\ninstance of the platform-specific path segment separator (/ on POSIX and\n\\ on Windows). Trailing separators are preserved.
If the path is a zero-length string, '.' is returned, representing the\ncurrent working directory.
For example, on POSIX:
\npath.normalize('/foo/bar//baz/asdf/quux/..');\n// Returns: '/foo/bar/baz/asdf'\nOn Windows:
\npath.normalize('C:\\\\temp\\\\\\\\foo\\\\bar\\\\..\\\\');\n// Returns: 'C:\\\\temp\\\\foo\\\\'\nSince Windows recognizes multiple path separators, both separators will be\nreplaced by instances of the Windows preferred separator (\\):
path.win32.normalize('C:////temp\\\\\\\\/\\\\/\\\\/foo/bar');\n// Returns: 'C:\\\\temp\\\\foo\\\\bar'\nA TypeError is thrown if path is not a string.
The path.parse() method returns an object whose properties represent\nsignificant elements of the path. Trailing directory separators are ignored,\nsee path.sep.
The returned object will have the following properties:
\n\nFor example, on POSIX:
\npath.parse('/home/user/dir/file.txt');\n// Returns:\n// { root: '/',\n// dir: '/home/user/dir',\n// base: 'file.txt',\n// ext: '.txt',\n// name: 'file' }\n┌─────────────────────┬────────────┐\n│ dir │ base │\n├──────┬ ├──────┬─────┤\n│ root │ │ name │ ext │\n\" / home/user/dir / file .txt \"\n└──────┴──────────────┴──────┴─────┘\n(all spaces in the \"\" line should be ignored — they are purely for formatting)\nOn Windows:
\npath.parse('C:\\\\path\\\\dir\\\\file.txt');\n// Returns:\n// { root: 'C:\\\\',\n// dir: 'C:\\\\path\\\\dir',\n// base: 'file.txt',\n// ext: '.txt',\n// name: 'file' }\n┌─────────────────────┬────────────┐\n│ dir │ base │\n├──────┬ ├──────┬─────┤\n│ root │ │ name │ ext │\n\" C:\\ path\\dir \\ file .txt \"\n└──────┴──────────────┴──────┴─────┘\n(all spaces in the \"\" line should be ignored — they are purely for formatting)\nA TypeError is thrown if path is not a string.
The path.relative() method returns the relative path from from to to based\non the current working directory. If from and to each resolve to the same\npath (after calling path.resolve() on each), a zero-length string is returned.
If a zero-length string is passed as from or to, the current working\ndirectory will be used instead of the zero-length strings.
For example, on POSIX:
\npath.relative('/data/orandea/test/aaa', '/data/orandea/impl/bbb');\n// Returns: '../../impl/bbb'\nOn Windows:
\npath.relative('C:\\\\orandea\\\\test\\\\aaa', 'C:\\\\orandea\\\\impl\\\\bbb');\n// Returns: '..\\\\..\\\\impl\\\\bbb'\nA TypeError is thrown if either from or to is not a string.
The path.resolve() method resolves a sequence of paths or path segments into\nan absolute path.
The given sequence of paths is processed from right to left, with each\nsubsequent path prepended until an absolute path is constructed.\nFor instance, given the sequence of path segments: /foo, /bar, baz,\ncalling path.resolve('/foo', '/bar', 'baz') would return /bar/baz.
If after processing all given path segments an absolute path has not yet\nbeen generated, the current working directory is used.
The resulting path is normalized and trailing slashes are removed unless the\npath is resolved to the root directory.
\nZero-length path segments are ignored.
If no path segments are passed, path.resolve() will return the absolute path\nof the current working directory.
path.resolve('/foo/bar', './baz');\n// Returns: '/foo/bar/baz'\n\npath.resolve('/foo/bar', '/tmp/file/');\n// Returns: '/tmp/file'\n\npath.resolve('wwwroot', 'static_files/png/', '../gif/image.gif');\n// if the current working directory is /home/myself/node,\n// this returns '/home/myself/node/wwwroot/static_files/gif/image.gif'\nA TypeError is thrown if any of the arguments is not a string.
On Windows systems only, returns an equivalent namespace-prefixed path for\nthe given path. If path is not a string, path will be returned without\nmodifications.
This method is meaningful only on Windows system. On POSIX systems, the\nmethod is non-operational and always returns path without modifications.
Provides the platform-specific path delimiter:
\n; for Windows: for POSIXFor example, on POSIX:
\nconsole.log(process.env.PATH);\n// Prints: '/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'\n\nprocess.env.PATH.split(path.delimiter);\n// Returns: ['/usr/bin', '/bin', '/usr/sbin', '/sbin', '/usr/local/bin']\nOn Windows:
\nconsole.log(process.env.PATH);\n// Prints: 'C:\\Windows\\system32;C:\\Windows;C:\\Program Files\\node\\'\n\nprocess.env.PATH.split(path.delimiter);\n// Returns ['C:\\\\Windows\\\\system32', 'C:\\\\Windows', 'C:\\\\Program Files\\\\node\\\\']\nThe path.posix property provides access to POSIX specific implementations\nof the path methods.
Provides the platform-specific path segment separator:
\n\\ on Windows/ on POSIXFor example, on POSIX:
\n'foo/bar/baz'.split(path.sep);\n// Returns: ['foo', 'bar', 'baz']\nOn Windows:
\n'foo\\\\bar\\\\baz'.split(path.sep);\n// Returns: ['foo', 'bar', 'baz']\nOn Windows, both the forward slash (/) and backward slash (\\) are accepted\nas path segment separators; however, the path methods only add backward\nslashes (\\).
The path.win32 property provides access to Windows-specific implementations\nof the path methods.
The Performance Timing API provides an implementation of the\nW3C Performance Timeline specification. The purpose of the API\nis to support collection of high resolution performance metrics.\nThis is the same Performance API as implemented in modern Web browsers.
\nconst { PerformanceObserver, performance } = require('perf_hooks');\n\nconst obs = new PerformanceObserver((items) => {\n console.log(items.getEntries()[0].duration);\n performance.clearMarks();\n});\nobs.observe({ entryTypes: ['measure'] });\n\nperformance.mark('A');\ndoSomeLongRunningProcess(() => {\n performance.mark('B');\n performance.measure('A to B', 'A', 'B');\n});\nIf name is not provided, removes all PerformanceMark objects from the\nPerformance Timeline. If name is provided, removes only the named mark.
Creates a new PerformanceMark entry in the Performance Timeline. A\nPerformanceMark is a subclass of PerformanceEntry whose\nperformanceEntry.entryType is always 'mark', and whose\nperformanceEntry.duration is always 0. Performance marks are used\nto mark specific significant moments in the Performance Timeline.
Creates a new PerformanceMeasure entry in the Performance Timeline. A\nPerformanceMeasure is a subclass of PerformanceEntry whose\nperformanceEntry.entryType is always 'measure', and whose\nperformanceEntry.duration measures the number of milliseconds elapsed since\nstartMark and endMark.
The startMark argument may identify any existing PerformanceMark in the\nPerformance Timeline, or may identify any of the timestamp properties\nprovided by the PerformanceNodeTiming class. If the named startMark does\nnot exist, then startMark is set to timeOrigin by default.
The endMark argument must identify any existing PerformanceMark in the\nPerformance Timeline or any of the timestamp properties provided by the\nPerformanceNodeTiming class. If the named endMark does not exist, an\nerror will be thrown.
Returns the current high resolution millisecond timestamp, where 0 represents\nthe start of the current node process.
Wraps a function within a new function that measures the running time of the\nwrapped function. A PerformanceObserver must be subscribed to the 'function'\nevent type in order for the timing details to be accessed.
const {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nfunction someFunction() {\n console.log('hello world');\n}\n\nconst wrapped = performance.timerify(someFunction);\n\nconst obs = new PerformanceObserver((list) => {\n console.log(list.getEntries()[0].duration);\n obs.disconnect();\n});\nobs.observe({ entryTypes: ['function'] });\n\n// A performance timeline entry will be created\nwrapped();\nAn instance of the PerformanceNodeTiming class that provides performance\nmetrics for specific Node.js operational milestones.
The timeOrigin specifies the high resolution millisecond timestamp at\nwhich the current node process began, measured in Unix time.
The total number of milliseconds elapsed for this entry. This value will not\nbe meaningful for all Performance Entry types.
" }, { "textRaw": "`name` {string}", "type": "string", "name": "name", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The name of the performance entry.
" }, { "textRaw": "`startTime` {number}", "type": "number", "name": "startTime", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp marking the starting time of the\nPerformance Entry.
" }, { "textRaw": "`entryType` {string}", "type": "string", "name": "entryType", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The type of the performance entry. Currently it may be one of: 'node',\n'mark', 'measure', 'gc', 'function', or 'http2'.
When performanceEntry.entryType is equal to 'gc', the performance.kind\nproperty identifies the type of garbage collection operation that occurred.\nThe value may be one of:
perf_hooks.constants.NODE_PERFORMANCE_GC_MAJORperf_hooks.constants.NODE_PERFORMANCE_GC_MINORperf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTALperf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCBProvides timing details for Node.js itself.
", "properties": [ { "textRaw": "`bootstrapComplete` {number}", "type": "number", "name": "bootstrapComplete", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js process\ncompleted bootstrapping. If bootstrapping has not yet finished, the property\nhas the value of -1.
" }, { "textRaw": "`loopExit` {number}", "type": "number", "name": "loopExit", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js event loop\nexited. If the event loop has not yet exited, the property has the value of -1.\nIt can only have a value of not -1 in a handler of the 'exit' event.
The high resolution millisecond timestamp at which the Node.js event loop\nstarted. If the event loop has not yet started (e.g., in the first tick of the\nmain script), the property has the value of -1.
" }, { "textRaw": "`nodeStart` {number}", "type": "number", "name": "nodeStart", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the Node.js process was\ninitialized.
" }, { "textRaw": "`v8Start` {number}", "type": "number", "name": "v8Start", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "desc": "The high resolution millisecond timestamp at which the V8 platform was\ninitialized.
" } ] }, { "textRaw": "Class: PerformanceObserver", "type": "class", "name": "PerformanceObserver", "methods": [ { "textRaw": "performanceObserver.disconnect()", "type": "method", "name": "disconnect", "meta": { "added": [ "v8.5.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Disconnects the PerformanceObserver instance from all notifications.
Subscribes the PerformanceObserver instance to notifications of new\nPerformanceEntry instances identified by options.entryTypes.
When options.buffered is false, the callback will be invoked once for\nevery PerformanceEntry instance:
const {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n // called three times synchronously. list contains one item\n});\nobs.observe({ entryTypes: ['mark'] });\n\nfor (let n = 0; n < 3; n++)\n performance.mark(`test${n}`);\nconst {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n // called once. list contains three items\n});\nobs.observe({ entryTypes: ['mark'], buffered: true });\n\nfor (let n = 0; n < 3; n++)\n performance.mark(`test${n}`);\nPerformanceObserver objects provide notifications when new\nPerformanceEntry instances have been added to the Performance Timeline.
const {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst obs = new PerformanceObserver((list, observer) => {\n console.log(list.getEntries());\n observer.disconnect();\n});\nobs.observe({ entryTypes: ['mark'], buffered: true });\n\nperformance.mark('test');\nBecause PerformanceObserver instances introduce their own additional\nperformance overhead, instances should not be left subscribed to notifications\nindefinitely. Users should disconnect observers as soon as they are no\nlonger needed.
The callback is invoked when a PerformanceObserver is\nnotified about new PerformanceEntry instances. The callback receives a\nPerformanceObserverEntryList instance and a reference to the\nPerformanceObserver.
The PerformanceObserverEntryList class is used to provide access to the\nPerformanceEntry instances passed to a PerformanceObserver.
Returns a list of PerformanceEntry objects in chronological order\nwith respect to performanceEntry.startTime.
Returns a list of PerformanceEntry objects in chronological order\nwith respect to performanceEntry.startTime whose performanceEntry.name is\nequal to name, and optionally, whose performanceEntry.entryType is equal to\ntype.
Returns a list of PerformanceEntry objects in chronological order\nwith respect to performanceEntry.startTime whose performanceEntry.entryType\nis equal to type.
The following example uses the Async Hooks and Performance APIs to measure\nthe actual duration of a Timeout operation (including the amount of time it\nto execute the callback).
\n'use strict';\nconst async_hooks = require('async_hooks');\nconst {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\n\nconst set = new Set();\nconst hook = async_hooks.createHook({\n init(id, type) {\n if (type === 'Timeout') {\n performance.mark(`Timeout-${id}-Init`);\n set.add(id);\n }\n },\n destroy(id) {\n if (set.has(id)) {\n set.delete(id);\n performance.mark(`Timeout-${id}-Destroy`);\n performance.measure(`Timeout-${id}`,\n `Timeout-${id}-Init`,\n `Timeout-${id}-Destroy`);\n }\n }\n});\nhook.enable();\n\nconst obs = new PerformanceObserver((list, observer) => {\n console.log(list.getEntries()[0]);\n performance.clearMarks();\n observer.disconnect();\n});\nobs.observe({ entryTypes: ['measure'], buffered: true });\n\nsetTimeout(() => {}, 1000);\nThe following example measures the duration of require() operations to load\ndependencies:
'use strict';\nconst {\n performance,\n PerformanceObserver\n} = require('perf_hooks');\nconst mod = require('module');\n\n// Monkey patch the require function\nmod.Module.prototype.require =\n performance.timerify(mod.Module.prototype.require);\nrequire = performance.timerify(require);\n\n// Activate the observer\nconst obs = new PerformanceObserver((list) => {\n const entries = list.getEntries();\n entries.forEach((entry) => {\n console.log(`require('${entry[0]}')`, entry.duration);\n });\n obs.disconnect();\n});\nobs.observe({ entryTypes: ['function'], buffered: true });\n\nrequire('some-module');\nThe version of the punycode module bundled in Node.js is being deprecated.\nIn a future major version of Node.js this module will be removed. Users\ncurrently depending on the punycode module should switch to using the\nuserland-provided Punycode.js module instead.
The punycode module is a bundled version of the Punycode.js module. It\ncan be accessed using:
const punycode = require('punycode');\nPunycode is a character encoding scheme defined by RFC 3492 that is\nprimarily intended for use in Internationalized Domain Names. Because host\nnames in URLs are limited to ASCII characters only, Domain Names that contain\nnon-ASCII characters must be converted into ASCII using the Punycode scheme.\nFor instance, the Japanese character that translates into the English word,\n'example' is '例'. The Internationalized Domain Name, '例.com' (equivalent\nto 'example.com') is represented by Punycode as the ASCII string\n'xn--fsq.com'.
The punycode module provides a simple implementation of the Punycode standard.
The punycode module is a third-party dependency used by Node.js and\nmade available to developers as a convenience. Fixes or other modifications to\nthe module must be directed to the Punycode.js project.
The punycode.decode() method converts a Punycode string of ASCII-only\ncharacters to the equivalent string of Unicode codepoints.
punycode.decode('maana-pta'); // 'mañana'\npunycode.decode('--dqo34k'); // '☃-⌘'\nThe punycode.encode() method converts a string of Unicode codepoints to a\nPunycode string of ASCII-only characters.
punycode.encode('mañana'); // 'maana-pta'\npunycode.encode('☃-⌘'); // '--dqo34k'\nThe punycode.toASCII() method converts a Unicode string representing an\nInternationalized Domain Name to Punycode. Only the non-ASCII parts of the\ndomain name will be converted. Calling punycode.toASCII() on a string that\nalready only contains ASCII characters will have no effect.
// encode domain names\npunycode.toASCII('mañana.com'); // 'xn--maana-pta.com'\npunycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'\npunycode.toASCII('example.com'); // 'example.com'\nThe punycode.toUnicode() method converts a string representing a domain name\ncontaining Punycode encoded characters into Unicode. Only the Punycode\nencoded parts of the domain name are be converted.
// decode domain names\npunycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'\npunycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'\npunycode.toUnicode('example.com'); // 'example.com'\nThe punycode.ucs2.decode() method returns an array containing the numeric\ncodepoint values of each Unicode symbol in the string.
punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]\n// surrogate pair for U+1D306 tetragram for centre:\npunycode.ucs2.decode('\\uD834\\uDF06'); // [0x1D306]\nThe punycode.ucs2.encode() method returns a string based on an array of\nnumeric code point values.
punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'\npunycode.ucs2.encode([0x1D306]); // '\\uD834\\uDF06'\nReturns a string identifying the current Punycode.js version number.
" } ], "type": "module", "displayName": "Punycode" }, { "textRaw": "Query String", "name": "querystring", "introduced_in": "v0.10.0", "stability": 2, "stabilityText": "Stable", "desc": "The querystring module provides utilities for parsing and formatting URL\nquery strings. It can be accessed using:
const querystring = require('querystring');\nThe querystring.decode() function is an alias for querystring.parse().
The querystring.encode() function is an alias for querystring.stringify().
The querystring.escape() method performs URL percent-encoding on the given\nstr in a manner that is optimized for the specific requirements of URL\nquery strings.
The querystring.escape() method is used by querystring.stringify() and is\ngenerally not expected to be used directly. It is exported primarily to allow\napplication code to provide a replacement percent-encoding implementation if\nnecessary by assigning querystring.escape to an alternative function.
The querystring.parse() method parses a URL query string (str) into a\ncollection of key and value pairs.
For example, the query string 'foo=bar&abc=xyz&abc=123' is parsed into:
{\n foo: 'bar',\n abc: ['xyz', '123']\n}\nThe object returned by the querystring.parse() method does not\nprototypically inherit from the JavaScript Object. This means that typical\nObject methods such as obj.toString(), obj.hasOwnProperty(), and others\nare not defined and will not work.
By default, percent-encoded characters within the query string will be assumed\nto use UTF-8 encoding. If an alternative character encoding is used, then an\nalternative decodeURIComponent option will need to be specified:
// Assuming gbkDecodeURIComponent function already exists...\n\nquerystring.parse('w=%D6%D0%CE%C4&foo=bar', null, null,\n { decodeURIComponent: gbkDecodeURIComponent });\nThe querystring.stringify() method produces a URL query string from a\ngiven obj by iterating through the object's \"own properties\".
It serializes the following types of values passed in obj:\n<string> | <number> | <boolean> | <string[]> | <number[]> | <boolean[]>\nAny other input values will be coerced to empty strings.
querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' });\n// returns 'foo=bar&baz=qux&baz=quux&corge='\n\nquerystring.stringify({ foo: 'bar', baz: 'qux' }, ';', ':');\n// returns 'foo:bar;baz:qux'\nBy default, characters requiring percent-encoding within the query string will\nbe encoded as UTF-8. If an alternative encoding is required, then an alternative\nencodeURIComponent option will need to be specified:
// Assuming gbkEncodeURIComponent function already exists,\n\nquerystring.stringify({ w: '中文', foo: 'bar' }, null, null,\n { encodeURIComponent: gbkEncodeURIComponent });\nThe querystring.unescape() method performs decoding of URL percent-encoded\ncharacters on the given str.
The querystring.unescape() method is used by querystring.parse() and is\ngenerally not expected to be used directly. It is exported primarily to allow\napplication code to provide a replacement decoding implementation if\nnecessary by assigning querystring.unescape to an alternative function.
By default, the querystring.unescape() method will attempt to use the\nJavaScript built-in decodeURIComponent() method to decode. If that fails,\na safer equivalent that does not throw on malformed URLs will be used.
The readline module provides an interface for reading data from a Readable\nstream (such as process.stdin) one line at a time. It can be accessed using:
const readline = require('readline');\nThe following simple example illustrates the basic use of the readline module.
const readline = require('readline');\n\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout\n});\n\nrl.question('What do you think of Node.js? ', (answer) => {\n // TODO: Log the answer in a database\n console.log(`Thank you for your valuable feedback: ${answer}`);\n\n rl.close();\n});\nOnce this code is invoked, the Node.js application will not terminate until the\nreadline.Interface is closed because the interface waits for data to be\nreceived on the input stream.
Instances of the readline.Interface class are constructed using the\nreadline.createInterface() method. Every instance is associated with a\nsingle input Readable stream and a single output Writable stream.\nThe output stream is used to print prompts for user input that arrives on,\nand is read from, the input stream.
The 'close' event is emitted when one of the following occur:
rl.close() method is called and the readline.Interface instance has\nrelinquished control over the input and output streams;input stream receives its 'end' event;input stream receives <ctrl>-D to signal end-of-transmission (EOT);input stream receives <ctrl>-C to signal SIGINT and there is no\n'SIGINT' event listener registered on the readline.Interface instance.The listener function is called without passing any arguments.
\nThe readline.Interface instance is finished once the 'close' event is\nemitted.
The 'line' event is emitted whenever the input stream receives an\nend-of-line input (\\n, \\r, or \\r\\n). This usually occurs when the user\npresses the <Enter>, or <Return> keys.
The listener function is called with a string containing the single line of\nreceived input.
\nrl.on('line', (input) => {\n console.log(`Received: ${input}`);\n});\nThe 'pause' event is emitted when one of the following occur:
input stream is paused.input stream is not paused and receives the 'SIGCONT' event. (See\nevents 'SIGTSTP' and 'SIGCONT'.)The listener function is called without passing any arguments.
\nrl.on('pause', () => {\n console.log('Readline paused.');\n});\nThe 'resume' event is emitted whenever the input stream is resumed.
The listener function is called without passing any arguments.
\nrl.on('resume', () => {\n console.log('Readline resumed.');\n});\nThe 'SIGCONT' event is emitted when a Node.js process previously moved into\nthe background using <ctrl>-Z (i.e. SIGTSTP) is then brought back to the\nforeground using fg(1p).
If the input stream was paused before the SIGTSTP request, this event will\nnot be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGCONT', () => {\n // `prompt` will automatically resume the stream\n rl.prompt();\n});\nThe 'SIGCONT' event is not supported on Windows.
The 'SIGINT' event is emitted whenever the input stream receives a\n<ctrl>-C input, known typically as SIGINT. If there are no 'SIGINT' event\nlisteners registered when the input stream receives a SIGINT, the 'pause'\nevent will be emitted.
The listener function is invoked without passing any arguments.
\nrl.on('SIGINT', () => {\n rl.question('Are you sure you want to exit? ', (answer) => {\n if (answer.match(/^y(es)?$/i)) rl.pause();\n });\n});\nThe 'SIGTSTP' event is emitted when the input stream receives a <ctrl>-Z\ninput, typically known as SIGTSTP. If there are no 'SIGTSTP' event listeners\nregistered when the input stream receives a SIGTSTP, the Node.js process\nwill be sent to the background.
When the program is resumed using fg(1p), the 'pause' and 'SIGCONT' events\nwill be emitted. These can be used to resume the input stream.
The 'pause' and 'SIGCONT' events will not be emitted if the input was\npaused before the process was sent to the background.
The listener function is invoked without passing any arguments.
\nrl.on('SIGTSTP', () => {\n // This will override SIGTSTP and prevent the program from going to the\n // background.\n console.log('Caught SIGTSTP.');\n});\nThe 'SIGTSTP' event is not supported on Windows.
The rl.close() method closes the readline.Interface instance and\nrelinquishes control over the input and output streams. When called,\nthe 'close' event will be emitted.
Calling rl.close() does not immediately stop other events (including 'line')\nfrom being emitted by the readline.Interface instance.
The rl.pause() method pauses the input stream, allowing it to be resumed\nlater if necessary.
Calling rl.pause() does not immediately pause other events (including\n'line') from being emitted by the readline.Interface instance.
The rl.prompt() method writes the readline.Interface instances configured\nprompt to a new line in output in order to provide a user with a new\nlocation at which to provide input.
When called, rl.prompt() will resume the input stream if it has been\npaused.
If the readline.Interface was created with output set to null or\nundefined the prompt is not written.
The rl.question() method displays the query by writing it to the output,\nwaits for user input to be provided on input, then invokes the callback\nfunction passing the provided input as the first argument.
When called, rl.question() will resume the input stream if it has been\npaused.
If the readline.Interface was created with output set to null or\nundefined the query is not written.
Example usage:
\nrl.question('What is your favorite food? ', (answer) => {\n console.log(`Oh, so your favorite food is ${answer}`);\n});\nThe callback function passed to rl.question() does not follow the typical\npattern of accepting an Error object or null as the first argument.\nThe callback is called with the provided answer as the only argument.
The rl.resume() method resumes the input stream if it has been paused.
The rl.setPrompt() method sets the prompt that will be written to output\nwhenever rl.prompt() is called.
The rl.write() method will write either data or a key sequence identified\nby key to the output. The key argument is supported only if output is\na TTY text terminal.
If key is specified, data is ignored.
When called, rl.write() will resume the input stream if it has been\npaused.
If the readline.Interface was created with output set to null or\nundefined the data and key are not written.
rl.write('Delete this!');\n// Simulate Ctrl+u to delete the line written previously\nrl.write(null, { ctrl: true, name: 'u' });\nThe rl.write() method will write the data to the readline Interface's\ninput as if it were provided by the user.
Create an AsyncIterator object that iterates through each line in the input\nstream as a string. This method allows asynchronous iteration of\nreadline.Interface objects through for-await-of loops.
Errors in the input stream are not forwarded.
\nIf the loop is terminated with break, throw, or return,\nrl.close() will be called. In other words, iterating over a\nreadline.Interface will always consume the input stream fully.
A caveat with using this experimental API is that the performance is\ncurrently not on par with the traditional 'line' event API, and thus it is\nnot recommended for performance-sensitive applications. We expect this\nsituation to improve in the future.
async function processLineByLine() {\n const rl = readline.createInterface({\n // ...\n });\n\n for await (const line of rl) {\n // Each line in the readline input will be successively available here as\n // `line`.\n }\n}\nThe readline.clearLine() method clears current line of given TTY stream\nin a specified direction identified by dir.
The readline.clearScreenDown() method clears the given TTY stream from\nthe current position of the cursor down.
The readline.createInterface() method creates a new readline.Interface\ninstance.
const readline = require('readline');\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout\n});\nOnce the readline.Interface instance is created, the most common case is to\nlisten for the 'line' event:
rl.on('line', (line) => {\n console.log(`Received: ${line}`);\n});\nIf terminal is true for this instance then the output stream will get\nthe best compatibility if it defines an output.columns property and emits\na 'resize' event on the output if or when the columns ever change\n(process.stdout does this automatically when it is a TTY).
The completer function takes the current line entered by the user\nas an argument, and returns an Array with 2 entries:
Array with matching entries for the completion.For instance: [[substr1, substr2, ...], originalsubstring].
function completer(line) {\n const completions = '.help .error .exit .quit .q'.split(' ');\n const hits = completions.filter((c) => c.startsWith(line));\n // show all completions if none found\n return [hits.length ? hits : completions, line];\n}\nThe completer function can be called asynchronously if it accepts two\narguments:
function completer(linePartial, callback) {\n callback(null, [['123'], linePartial]);\n}\nThe readline.cursorTo() method moves cursor to the specified position in a\ngiven TTY stream.
The readline.emitKeypressEvents() method causes the given Readable\nstream to begin emitting 'keypress' events corresponding to received input.
Optionally, interface specifies a readline.Interface instance for which\nautocompletion is disabled when copy-pasted input is detected.
If the stream is a TTY, then it must be in raw mode.
This is automatically called by any readline instance on its input if the\ninput is a terminal. Closing the readline instance does not stop\nthe input from emitting 'keypress' events.
readline.emitKeypressEvents(process.stdin);\nif (process.stdin.isTTY)\n process.stdin.setRawMode(true);\nThe readline.moveCursor() method moves the cursor relative to its current\nposition in a given TTY stream.
The following example illustrates the use of readline.Interface class to\nimplement a small command-line interface:
const readline = require('readline');\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout,\n prompt: 'OHAI> '\n});\n\nrl.prompt();\n\nrl.on('line', (line) => {\n switch (line.trim()) {\n case 'hello':\n console.log('world!');\n break;\n default:\n console.log(`Say what? I might have heard '${line.trim()}'`);\n break;\n }\n rl.prompt();\n}).on('close', () => {\n console.log('Have a great day!');\n process.exit(0);\n});\nA common use case for readline is to consume an input file one line at a\ntime. The easiest way to do so is leveraging the fs.ReadStream API as\nwell as a for-await-of loop:
const fs = require('fs');\nconst readline = require('readline');\n\nasync function processLineByLine() {\n const fileStream = fs.createReadStream('input.txt');\n\n const rl = readline.createInterface({\n input: fileStream,\n crlfDelay: Infinity\n });\n // Note: we use the crlfDelay option to recognize all instances of CR LF\n // ('\\r\\n') in input.txt as a single line break.\n\n for await (const line of rl) {\n // Each line in input.txt will be successively available here as `line`.\n console.log(`Line from file: ${line}`);\n }\n}\n\nprocessLineByLine();\nAlternatively, one could use the 'line' event:
const fs = require('fs');\nconst readline = require('readline');\n\nconst rl = readline.createInterface({\n input: fs.createReadStream('sample.txt'),\n crlfDelay: Infinity\n});\n\nrl.on('line', (line) => {\n console.log(`Line from file: ${line}`);\n});\nCurrently, for-await-of loop can be a bit slower. If async / await\nflow and speed are both essential, a mixed approach can be applied:
const { once } = require('events');\nconst { createReadStream } = require('fs');\nconst { createInterface } = require('readline');\n\n(async function processLineByLine() {\n try {\n const rl = createInterface({\n input: createReadStream('big-file.txt'),\n crlfDelay: Infinity\n });\n\n rl.on('line', (line) => {\n // Process the line.\n });\n\n await once(rl, 'close');\n\n console.log('File processed.');\n } catch (err) {\n console.error(err);\n }\n})();\nThe repl module provides a Read-Eval-Print-Loop (REPL) implementation that\nis available both as a standalone program or includible in other applications.\nIt can be accessed using:
const repl = require('repl');\nThe repl module exports the repl.REPLServer class. While running,\ninstances of repl.REPLServer will accept individual lines of user input,\nevaluate those according to a user-defined evaluation function, then output the\nresult. Input and output may be from stdin and stdout, respectively, or may\nbe connected to any Node.js stream.
Instances of repl.REPLServer support automatic completion of inputs,\nsimplistic Emacs-style line editing, multi-line inputs, ANSI-styled output,\nsaving and restoring current REPL session state, error recovery, and\ncustomizable evaluation functions.
The following special commands are supported by all REPL instances:
\n.break - When in the process of inputting a multi-line expression, entering\nthe .break command (or pressing the <ctrl>-C key combination) will abort\nfurther input or processing of that expression..clear - Resets the REPL context to an empty object and clears any\nmulti-line expression currently being input..exit - Close the I/O stream, causing the REPL to exit..help - Show this list of special commands..save - Save the current REPL session to a file:\n> .save ./file/to/save.js.load - Load a file into the current REPL session.\n> .load ./file/to/load.js.editor - Enter editor mode (<ctrl>-D to finish, <ctrl>-C to cancel).> .editor\n// Entering editor mode (^D to finish, ^C to cancel)\nfunction welcome(name) {\n return `Hello ${name}!`;\n}\n\nwelcome('Node.js User');\n\n// ^D\n'Hello Node.js User!'\n>\nThe following key combinations in the REPL have these special effects:
\n<ctrl>-C - When pressed once, has the same effect as the .break command.\nWhen pressed twice on a blank line, has the same effect as the .exit\ncommand.<ctrl>-D - Has the same effect as the .exit command.<tab> - When pressed on a blank line, displays global and local (scope)\nvariables. When pressed while entering other input, displays relevant\nautocompletion options.By default, all instances of repl.REPLServer use an evaluation function\nthat evaluates JavaScript expressions and provides access to Node.js' built-in\nmodules. This default behavior can be overridden by passing in an alternative\nevaluation function when the repl.REPLServer instance is created.
The default evaluator supports direct evaluation of JavaScript expressions:
\n\n> 1 + 1\n2\n> const m = 2\nundefined\n> m + 1\n3\nUnless otherwise scoped within blocks or functions, variables declared\neither implicitly or using the const, let, or var keywords\nare declared at the global scope.
The default evaluator provides access to any variables that exist in the global\nscope. It is possible to expose a variable to the REPL explicitly by assigning\nit to the context object associated with each REPLServer:
const repl = require('repl');\nconst msg = 'message';\n\nrepl.start('> ').context.m = msg;\nProperties in the context object appear as local within the REPL:
$ node repl_test.js\n> m\n'message'\nContext properties are not read-only by default. To specify read-only globals,\ncontext properties must be defined using Object.defineProperty():
const repl = require('repl');\nconst msg = 'message';\n\nconst r = repl.start('> ');\nObject.defineProperty(r.context, 'm', {\n configurable: false,\n enumerable: true,\n value: msg\n});\nThe default evaluator will automatically load Node.js core modules into the\nREPL environment when used. For instance, unless otherwise declared as a\nglobal or scoped variable, the input fs will be evaluated on-demand as\nglobal.fs = require('fs').
> fs.createReadStream('./some/file');\nThe REPL uses the domain module to catch all uncaught exceptions for that\nREPL session.
This use of the domain module in the REPL has these side effects:
'uncaughtException' event.process.setUncaughtExceptionCaptureCallback() throws\nan ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE error.The default evaluator will, by default, assign the result of the most recently\nevaluated expression to the special variable _ (underscore).\nExplicitly setting _ to a value will disable this behavior.
> [ 'a', 'b', 'c' ]\n[ 'a', 'b', 'c' ]\n> _.length\n3\n> _ += 1\nExpression assignment to _ now disabled.\n4\n> 1 + 1\n2\n> _\n4\nSimilarly, _error will refer to the last seen error, if there was any.\nExplicitly setting _error to a value will disable this behavior.
> throw new Error('foo');\nError: foo\n> _error.message\n'foo'\nWith the --experimental-repl-await command line option specified,\nexperimental support for the await keyword is enabled.
> await Promise.resolve(123)\n123\n> await Promise.reject(new Error('REPL await'))\nError: REPL await\n at repl:1:45\n> const timeout = util.promisify(setTimeout);\nundefined\n> const old = Date.now(); await timeout(1000); console.log(Date.now() - old);\n1002\nundefined\nWhen a new repl.REPLServer is created, a custom evaluation function may be\nprovided. This can be used, for instance, to implement fully customized REPL\napplications.
The following illustrates a hypothetical example of a REPL that performs\ntranslation of text from one language to another:
\nconst repl = require('repl');\nconst { Translator } = require('translator');\n\nconst myTranslator = new Translator('en', 'fr');\n\nfunction myEval(cmd, context, filename, callback) {\n callback(null, myTranslator.translate(cmd));\n}\n\nrepl.start({ prompt: '> ', eval: myEval });\nAs a user is typing input into the REPL prompt, pressing the <enter> key will\nsend the current line of input to the eval function. In order to support\nmulti-line input, the eval function can return an instance of repl.Recoverable\nto the provided callback function:
function myEval(cmd, context, filename, callback) {\n let result;\n try {\n result = vm.runInThisContext(cmd);\n } catch (e) {\n if (isRecoverableError(e)) {\n return callback(new repl.Recoverable(e));\n }\n }\n callback(null, result);\n}\n\nfunction isRecoverableError(error) {\n if (error.name === 'SyntaxError') {\n return /^(Unexpected end of input|Unexpected token)/.test(error.message);\n }\n return false;\n}\nBy default, repl.REPLServer instances format output using the\nutil.inspect() method before writing the output to the provided Writable\nstream (process.stdout by default). The useColors boolean option can be\nspecified at construction to instruct the default writer to use ANSI style\ncodes to colorize the output from the util.inspect() method.
It is possible to fully customize the output of a repl.REPLServer instance\nby passing a new function in using the writer option on construction. The\nfollowing example, for instance, simply converts any input text to upper case:
const repl = require('repl');\n\nconst r = repl.start({ prompt: '> ', eval: myEval, writer: myWriter });\n\nfunction myEval(cmd, context, filename, callback) {\n callback(null, cmd);\n}\n\nfunction myWriter(output) {\n return output.toUpperCase();\n}\nNode.js itself uses the repl module to provide its own interactive interface\nfor executing JavaScript. This can be used by executing the Node.js binary\nwithout passing any arguments (or by passing the -i argument):
$ node\n> const a = [1, 2, 3];\nundefined\n> a\n[ 1, 2, 3 ]\n> a.forEach((v) => {\n... console.log(v);\n... });\n1\n2\n3\nVarious behaviors of the Node.js REPL can be customized using the following\nenvironment variables:
\nNODE_REPL_HISTORY - When a valid path is given, persistent REPL history\nwill be saved to the specified file rather than .node_repl_history in the\nuser's home directory. Setting this value to '' (an empty string) will\ndisable persistent REPL history. Whitespace will be trimmed from the value.\nOn Windows platforms environment variables with empty values are invalid so\nset this variable to one or more spaces to disable persistent REPL history.NODE_REPL_HISTORY_SIZE - Controls how many lines of history will be\npersisted if history is available. Must be a positive number.\nDefault: 1000.NODE_REPL_MODE - May be either 'sloppy' or 'strict'. Default:\n'sloppy', which will allow non-strict mode code to be run.By default, the Node.js REPL will persist history between node REPL sessions\nby saving inputs to a .node_repl_history file located in the user's home\ndirectory. This can be disabled by setting the environment variable\nNODE_REPL_HISTORY=''.
For advanced line-editors, start Node.js with the environment variable\nNODE_NO_READLINE=1. This will start the main and debugger REPL in canonical\nterminal settings, which will allow use with rlwrap.
For example, the following can be added to a .bashrc file:
alias node=\"env NODE_NO_READLINE=1 rlwrap node\"\nIt is possible to create and run multiple REPL instances against a single\nrunning instance of Node.js that share a single global object but have\nseparate I/O interfaces.
The following example, for instance, provides separate REPLs on stdin, a Unix\nsocket, and a TCP socket:
const net = require('net');\nconst repl = require('repl');\nlet connections = 0;\n\nrepl.start({\n prompt: 'Node.js via stdin> ',\n input: process.stdin,\n output: process.stdout\n});\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via Unix socket> ',\n input: socket,\n output: socket\n }).on('exit', () => {\n socket.end();\n });\n}).listen('/tmp/node-repl-sock');\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via TCP socket> ',\n input: socket,\n output: socket\n }).on('exit', () => {\n socket.end();\n });\n}).listen(5001);\nRunning this application from the command line will start a REPL on stdin.\nOther REPL clients may connect through the Unix socket or TCP socket. telnet,\nfor instance, is useful for connecting to TCP sockets, while socat can be used\nto connect to both Unix and TCP sockets.
By starting a REPL from a Unix socket-based server instead of stdin, it is\npossible to connect to a long-running Node.js process without restarting it.
\nFor an example of running a \"full-featured\" (terminal) REPL over\na net.Server and net.Socket instance, see:\nhttps://gist.github.com/TooTallNate/2209310.
For an example of running a REPL instance over curl(1), see:\nhttps://gist.github.com/TooTallNate/2053342.
The repl.REPLServer class inherits from the readline.Interface class.\nInstances of repl.REPLServer are created using the repl.start() method and\nshould not be created directly using the JavaScript new keyword.
The 'exit' event is emitted when the REPL is exited either by receiving the\n.exit command as input, the user pressing <ctrl>-C twice to signal SIGINT,\nor by pressing <ctrl>-D to signal 'end' on the input stream. The listener\ncallback is invoked without any arguments.
replServer.on('exit', () => {\n console.log('Received \"exit\" event from repl!');\n process.exit();\n});\nThe 'reset' event is emitted when the REPL's context is reset. This occurs\nwhenever the .clear command is received as input unless the REPL is using\nthe default evaluator and the repl.REPLServer instance was created with the\nuseGlobal option set to true. The listener callback will be called with a\nreference to the context object as the only argument.
This can be used primarily to re-initialize REPL context to some pre-defined\nstate:
\nconst repl = require('repl');\n\nfunction initializeContext(context) {\n context.m = 'test';\n}\n\nconst r = repl.start({ prompt: '> ' });\ninitializeContext(r.context);\n\nr.on('reset', initializeContext);\nWhen this code is executed, the global 'm' variable can be modified but then\nreset to its initial value using the .clear command:
$ ./node example.js\n> m\n'test'\n> m = 1\n1\n> m\n1\n> .clear\nClearing context...\n> m\n'test'\n>\nThe replServer.defineCommand() method is used to add new .-prefixed commands\nto the REPL instance. Such commands are invoked by typing a . followed by the\nkeyword. The cmd is either a Function or an Object with the following\nproperties:
help <string> Help text to be displayed when .help is entered (Optional).action <Function> The function to execute, optionally accepting a single\nstring argument.The following example shows two new commands added to the REPL instance:
\nconst repl = require('repl');\n\nconst replServer = repl.start({ prompt: '> ' });\nreplServer.defineCommand('sayhello', {\n help: 'Say hello',\n action(name) {\n this.clearBufferedCommand();\n console.log(`Hello, ${name}!`);\n this.displayPrompt();\n }\n});\nreplServer.defineCommand('saybye', function saybye() {\n console.log('Goodbye!');\n this.close();\n});\nThe new commands can then be used from within the REPL instance:
\n> .sayhello Node.js User\nHello, Node.js User!\n> .saybye\nGoodbye!\nThe replServer.displayPrompt() method readies the REPL instance for input\nfrom the user, printing the configured prompt to a new line in the output\nand resuming the input to accept new input.
When multi-line input is being entered, an ellipsis is printed rather than the\n'prompt'.
\nWhen preserveCursor is true, the cursor placement will not be reset to 0.
The replServer.displayPrompt method is primarily intended to be called from\nwithin the action function for commands registered using the\nreplServer.defineCommand() method.
The replServer.clearBufferedCommand() method clears any command that has been\nbuffered but not yet executed. This method is primarily intended to be\ncalled from within the action function for commands registered using the\nreplServer.defineCommand() method.
An internal method used to parse and execute REPLServer keywords.\nReturns true if keyword is a valid keyword, otherwise false.
The repl.start() method creates and starts a repl.REPLServer instance.
If options is a string, then it specifies the input prompt:
const repl = require('repl');\n\n// a Unix style prompt\nrepl.start('$ ');\nA stream is an abstract interface for working with streaming data in Node.js.\nThe stream module provides a base API that makes it easy to build objects\nthat implement the stream interface.
There are many stream objects provided by Node.js. For instance, a\nrequest to an HTTP server and process.stdout\nare both stream instances.
Streams can be readable, writable, or both. All streams are instances of\nEventEmitter.
The stream module can be accessed using:
const stream = require('stream');\nWhile it is important to understand how streams work, the stream module itself\nis most useful for developers that are creating new types of stream instances.\nDevelopers who are primarily consuming stream objects will rarely need to use\nthe stream module directly.
This document is divided into two primary sections with a third section for\nadditional notes. The first section explains the elements of the stream API that\nare required to use streams within an application. The second section explains\nthe elements of the API that are required to implement new types of streams.
", "type": "module", "displayName": "Organization of this Document" }, { "textRaw": "Types of Streams", "name": "types_of_streams", "desc": "There are four fundamental stream types within Node.js:
\nWritable - streams to which data can be written (for example,\nfs.createWriteStream()).Readable - streams from which data can be read (for example,\nfs.createReadStream()).Duplex - streams that are both Readable and Writable (for example,\nnet.Socket).Transform - Duplex streams that can modify or transform the data as it\nis written and read (for example, zlib.createDeflate()).Additionally, this module includes the utility functions pipeline,\nfinished and Readable.from.
", "modules": [ { "textRaw": "Object Mode", "name": "object_mode", "desc": "All streams created by Node.js APIs operate exclusively on strings and Buffer\n(or Uint8Array) objects. It is possible, however, for stream implementations\nto work with other types of JavaScript values (with the exception of null,\nwhich serves a special purpose within streams). Such streams are considered to\noperate in \"object mode\".
Stream instances are switched into object mode using the objectMode option\nwhen the stream is created. Attempting to switch an existing stream into\nobject mode is not safe.
Both Writable and Readable streams will store data in an internal\nbuffer that can be retrieved using writable.writableBuffer or\nreadable.readableBuffer, respectively.
The amount of data potentially buffered depends on the highWaterMark option\npassed into the stream's constructor. For normal streams, the highWaterMark\noption specifies a total number of bytes. For streams operating\nin object mode, the highWaterMark specifies a total number of objects.
Data is buffered in Readable streams when the implementation calls\nstream.push(chunk). If the consumer of the Stream does not\ncall stream.read(), the data will sit in the internal\nqueue until it is consumed.
Once the total size of the internal read buffer reaches the threshold specified\nby highWaterMark, the stream will temporarily stop reading data from the\nunderlying resource until the data currently buffered can be consumed (that is,\nthe stream will stop calling the internal readable._read() method that is\nused to fill the read buffer).
Data is buffered in Writable streams when the\nwritable.write(chunk) method is called repeatedly. While the\ntotal size of the internal write buffer is below the threshold set by\nhighWaterMark, calls to writable.write() will return true. Once\nthe size of the internal buffer reaches or exceeds the highWaterMark, false\nwill be returned.
A key goal of the stream API, particularly the stream.pipe() method,\nis to limit the buffering of data to acceptable levels such that sources and\ndestinations of differing speeds will not overwhelm the available memory.
Because Duplex and Transform streams are both Readable and\nWritable, each maintains two separate internal buffers used for reading and\nwriting, allowing each side to operate independently of the other while\nmaintaining an appropriate and efficient flow of data. For example,\nnet.Socket instances are Duplex streams whose Readable side allows\nconsumption of data received from the socket and whose Writable side allows\nwriting data to the socket. Because data may be written to the socket at a\nfaster or slower rate than data is received, it is important for each side to\noperate (and buffer) independently of the other.
A function to get notified when a stream is no longer readable, writable\nor has experienced an error or a premature close event.
\nconst { finished } = require('stream');\n\nconst rs = fs.createReadStream('archive.tar');\n\nfinished(rs, (err) => {\n if (err) {\n console.error('Stream failed.', err);\n } else {\n console.log('Stream is done reading.');\n }\n});\n\nrs.resume(); // drain the stream\nEspecially useful in error handling scenarios where a stream is destroyed\nprematurely (like an aborted HTTP request), and will not emit 'end'\nor 'finish'.
The finished API is promisify-able as well;
const finished = util.promisify(stream.finished);\n\nconst rs = fs.createReadStream('archive.tar');\n\nasync function run() {\n await finished(rs);\n console.log('Stream is done reading.');\n}\n\nrun().catch(console.error);\nrs.resume(); // drain the stream\nA module method to pipe between streams forwarding errors and properly cleaning\nup and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('stream');\nconst fs = require('fs');\nconst zlib = require('zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n }\n);\nThe pipeline API is promisify-able as well:
const pipeline = util.promisify(stream.pipeline);\n\nasync function run() {\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz')\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\nA utility method for creating Readable Streams out of iterators.
\nconst { Readable } = require('stream');\n\nasync function * generate() {\n yield 'hello';\n yield 'streams';\n}\n\nconst readable = Readable.from(generate());\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\nAlmost all Node.js applications, no matter how simple, use streams in some\nmanner. The following is an example of using streams in a Node.js application\nthat implements an HTTP server:
\nconst http = require('http');\n\nconst server = http.createServer((req, res) => {\n // req is an http.IncomingMessage, which is a Readable Stream\n // res is an http.ServerResponse, which is a Writable Stream\n\n let body = '';\n // Get the data as utf8 strings.\n // If an encoding is not set, Buffer objects will be received.\n req.setEncoding('utf8');\n\n // Readable streams emit 'data' events once a listener is added\n req.on('data', (chunk) => {\n body += chunk;\n });\n\n // the 'end' event indicates that the entire body has been received\n req.on('end', () => {\n try {\n const data = JSON.parse(body);\n // write back something interesting to the user:\n res.write(typeof data);\n res.end();\n } catch (er) {\n // uh oh! bad json!\n res.statusCode = 400;\n return res.end(`error: ${er.message}`);\n }\n });\n});\n\nserver.listen(1337);\n\n// $ curl localhost:1337 -d \"{}\"\n// object\n// $ curl localhost:1337 -d \"\\\"foo\\\"\"\n// string\n// $ curl localhost:1337 -d \"not json\"\n// error: Unexpected token o in JSON at position 1\nWritable streams (such as res in the example) expose methods such as\nwrite() and end() that are used to write data onto the stream.
Readable streams use the EventEmitter API for notifying application\ncode when data is available to be read off the stream. That available data can\nbe read from the stream in multiple ways.
Both Writable and Readable streams use the EventEmitter API in\nvarious ways to communicate the current state of the stream.
Duplex and Transform streams are both Writable and\nReadable.
Applications that are either writing data to or consuming data from a stream\nare not required to implement the stream interfaces directly and will generally\nhave no reason to call require('stream').
Developers wishing to implement new types of streams should refer to the\nsection API for Stream Implementers.
", "miscs": [ { "textRaw": "Writable Streams", "name": "writable_streams", "desc": "Writable streams are an abstraction for a destination to which data is\nwritten.
\nExamples of Writable streams include:
process.stdout, process.stderrSome of these examples are actually Duplex streams that implement the\nWritable interface.
All Writable streams implement the interface defined by the\nstream.Writable class.
While specific instances of Writable streams may differ in various ways,\nall Writable streams follow the same fundamental usage pattern as illustrated\nin the example below:
const myStream = getWritableStreamSomehow();\nmyStream.write('some data');\nmyStream.write('some more data');\nmyStream.end('done writing data');\nThe 'close' event is emitted when the stream and any of its underlying\nresources (a file descriptor, for example) have been closed. The event indicates\nthat no more events will be emitted, and no further computation will occur.
A Writable stream will always emit the 'close' event if it is\ncreated with the emitClose option.
If a call to stream.write(chunk) returns false, the\n'drain' event will be emitted when it is appropriate to resume writing data\nto the stream.
// Write the data to the supplied writable stream one million times.\n// Be attentive to back-pressure.\nfunction writeOneMillionTimes(writer, data, encoding, callback) {\n let i = 1000000;\n write();\n function write() {\n let ok = true;\n do {\n i--;\n if (i === 0) {\n // last time!\n writer.write(data, encoding, callback);\n } else {\n // see if we should continue, or wait\n // don't pass the callback, because we're not done yet.\n ok = writer.write(data, encoding);\n }\n } while (i > 0 && ok);\n if (i > 0) {\n // had to stop early!\n // write some more once it drains\n writer.once('drain', write);\n }\n }\n}\nThe 'error' event is emitted if an error occurred while writing or piping\ndata. The listener callback is passed a single Error argument when called.
The stream is not closed when the 'error' event is emitted.
The 'finish' event is emitted after the stream.end() method\nhas been called, and all data has been flushed to the underlying system.
const writer = getWritableStreamSomehow();\nfor (let i = 0; i < 100; i++) {\n writer.write(`hello, #${i}!\\n`);\n}\nwriter.end('This is the end\\n');\nwriter.on('finish', () => {\n console.log('All writes are now complete.');\n});\nThe 'pipe' event is emitted when the stream.pipe() method is called on\na readable stream, adding this writable to its set of destinations.
const writer = getWritableStreamSomehow();\nconst reader = getReadableStreamSomehow();\nwriter.on('pipe', (src) => {\n console.log('Something is piping into the writer.');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\nThe 'unpipe' event is emitted when the stream.unpipe() method is called\non a Readable stream, removing this Writable from its set of\ndestinations.
This is also emitted in case this Writable stream emits an error when a\nReadable stream pipes into it.
const writer = getWritableStreamSomehow();\nconst reader = getReadableStreamSomehow();\nwriter.on('unpipe', (src) => {\n console.log('Something has stopped piping into the writer.');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\nreader.unpipe(writer);\nThe writable.cork() method forces all written data to be buffered in memory.\nThe buffered data will be flushed when either the stream.uncork() or\nstream.end() methods are called.
The primary intent of writable.cork() is to avoid a situation where writing\nmany small chunks of data to a stream do not cause a backup in the internal\nbuffer that would have an adverse impact on performance. In such situations,\nimplementations that implement the writable._writev() method can perform\nbuffered writes in a more optimized manner.
See also: writable.uncork().
Destroy the stream, and emit the passed 'error' and a 'close' event.\nAfter this call, the writable stream has ended and subsequent calls\nto write() or end() will result in an ERR_STREAM_DESTROYED error.\nImplementors should not override this method,\nbut instead implement writable._destroy().
Calling the writable.end() method signals that no more data will be written\nto the Writable. The optional chunk and encoding arguments allow one\nfinal additional chunk of data to be written immediately before closing the\nstream. If provided, the optional callback function is attached as a listener\nfor the 'finish' event.
Calling the stream.write() method after calling\nstream.end() will raise an error.
// write 'hello, ' and then end with 'world!'\nconst fs = require('fs');\nconst file = fs.createWriteStream('example.txt');\nfile.write('hello, ');\nfile.end('world!');\n// writing more now is not allowed!\nThe writable.setDefaultEncoding() method sets the default encoding for a\nWritable stream.
The writable.uncork() method flushes all data buffered since\nstream.cork() was called.
When using writable.cork() and writable.uncork() to manage the buffering\nof writes to a stream, it is recommended that calls to writable.uncork() be\ndeferred using process.nextTick(). Doing so allows batching of all\nwritable.write() calls that occur within a given Node.js event loop phase.
stream.cork();\nstream.write('some ');\nstream.write('data ');\nprocess.nextTick(() => stream.uncork());\nIf the writable.cork() method is called multiple times on a stream, the\nsame number of calls to writable.uncork() must be called to flush the buffered\ndata.
stream.cork();\nstream.write('some ');\nstream.cork();\nstream.write('data ');\nprocess.nextTick(() => {\n stream.uncork();\n // The data will not be flushed until uncork() is called a second time.\n stream.uncork();\n});\nSee also: writable.cork().
The writable.write() method writes some data to the stream, and calls the\nsupplied callback once the data has been fully handled. If an error\noccurs, the callback may or may not be called with the error as its\nfirst argument. To reliably detect write errors, add a listener for the\n'error' event.
The return value is true if the internal buffer is less than the\nhighWaterMark configured when the stream was created after admitting chunk.\nIf false is returned, further attempts to write data to the stream should\nstop until the 'drain' event is emitted.
While a stream is not draining, calls to write() will buffer chunk, and\nreturn false. Once all currently buffered chunks are drained (accepted for\ndelivery by the operating system), the 'drain' event will be emitted.\nIt is recommended that once write() returns false, no more chunks be written\nuntil the 'drain' event is emitted. While calling write() on a stream that\nis not draining is allowed, Node.js will buffer all written chunks until\nmaximum memory usage occurs, at which point it will abort unconditionally.\nEven before it aborts, high memory usage will cause poor garbage collector\nperformance and high RSS (which is not typically released back to the system,\neven after the memory is no longer required). Since TCP sockets may never\ndrain if the remote peer does not read the data, writing a socket that is\nnot draining may lead to a remotely exploitable vulnerability.
Writing data while the stream is not draining is particularly\nproblematic for a Transform, because the Transform streams are paused\nby default until they are piped or a 'data' or 'readable' event handler\nis added.
If the data to be written can be generated or fetched on demand, it is\nrecommended to encapsulate the logic into a Readable and use\nstream.pipe(). However, if calling write() is preferred, it is\npossible to respect backpressure and avoid memory issues using the\n'drain' event:
function write(data, cb) {\n if (!stream.write(data)) {\n stream.once('drain', cb);\n } else {\n process.nextTick(cb);\n }\n}\n\n// Wait for cb to be called before doing any other write.\nwrite('hello', () => {\n console.log('Write completed, do more writes now.');\n});\nA Writable stream in object mode will always ignore the encoding argument.
Is true if it is safe to call [writable.write()][].
Return the value of highWaterMark passed when constructing this\nWritable.
This property contains the number of bytes (or objects) in the queue\nready to be written. The value provides introspection data regarding\nthe status of the highWaterMark.
Readable streams are an abstraction for a source from which data is\nconsumed.
\nExamples of Readable streams include:
process.stdinAll Readable streams implement the interface defined by the\nstream.Readable class.
Readable streams effectively operate in one of two modes: flowing and\npaused. These modes are separate from object mode.\nA Readable stream can be in object mode or not, regardless of whether\nit is in flowing mode or paused mode.
In flowing mode, data is read from the underlying system automatically\nand provided to an application as quickly as possible using events via the\nEventEmitter interface.
In paused mode, the stream.read() method must be called\nexplicitly to read chunks of data from the stream.
All Readable streams begin in paused mode but can be switched to flowing\nmode in one of the following ways:
'data' event handler.stream.resume() method.stream.pipe() method to send the data to a Writable.The Readable can switch back to paused mode using one of the following:
stream.pause() method.stream.unpipe() method.The important concept to remember is that a Readable will not generate data\nuntil a mechanism for either consuming or ignoring that data is provided. If\nthe consuming mechanism is disabled or taken away, the Readable will attempt\nto stop generating the data.
For backward compatibility reasons, removing 'data' event handlers will\nnot automatically pause the stream. Also, if there are piped destinations,\nthen calling stream.pause() will not guarantee that the\nstream will remain paused once those destinations drain and ask for more data.
If a Readable is switched into flowing mode and there are no consumers\navailable to handle the data, that data will be lost. This can occur, for\ninstance, when the readable.resume() method is called without a listener\nattached to the 'data' event, or when a 'data' event handler is removed\nfrom the stream.
Adding a 'readable' event handler automatically make the stream to\nstop flowing, and the data to be consumed via\nreadable.read(). If the 'readable' event handler is\nremoved, then the stream will start flowing again if there is a\n'data' event handler.
The \"two modes\" of operation for a Readable stream are a simplified\nabstraction for the more complicated internal state management that is happening\nwithin the Readable stream implementation.
Specifically, at any given point in time, every Readable is in one of three\npossible states:
readable.readableFlowing === nullreadable.readableFlowing === falsereadable.readableFlowing === trueWhen readable.readableFlowing is null, no mechanism for consuming the\nstream's data is provided. Therefore, the stream will not generate data.\nWhile in this state, attaching a listener for the 'data' event, calling the\nreadable.pipe() method, or calling the readable.resume() method will switch\nreadable.readableFlowing to true, causing the Readable to begin actively\nemitting events as data is generated.
Calling readable.pause(), readable.unpipe(), or receiving backpressure\nwill cause the readable.readableFlowing to be set as false,\ntemporarily halting the flowing of events but not halting the generation of\ndata. While in this state, attaching a listener for the 'data' event\nwill not switch readable.readableFlowing to true.
const { PassThrough, Writable } = require('stream');\nconst pass = new PassThrough();\nconst writable = new Writable();\n\npass.pipe(writable);\npass.unpipe(writable);\n// readableFlowing is now false\n\npass.on('data', (chunk) => { console.log(chunk.toString()); });\npass.write('ok'); // will not emit 'data'\npass.resume(); // must be called to make stream emit 'data'\nWhile readable.readableFlowing is false, data may be accumulating\nwithin the stream's internal buffer.
The Readable stream API evolved across multiple Node.js versions and provides\nmultiple methods of consuming stream data. In general, developers should choose\none of the methods of consuming data and should never use multiple methods\nto consume data from a single stream. Specifically, using a combination\nof on('data'), on('readable'), pipe(), or async iterators could\nlead to unintuitive behavior.
Use of the readable.pipe() method is recommended for most users as it has been\nimplemented to provide the easiest way of consuming stream data. Developers that\nrequire more fine-grained control over the transfer and generation of data can\nuse the EventEmitter and readable.on('readable')/readable.read()\nor the readable.pause()/readable.resume() APIs.
The 'close' event is emitted when the stream and any of its underlying\nresources (a file descriptor, for example) have been closed. The event indicates\nthat no more events will be emitted, and no further computation will occur.
A Readable stream will always emit the 'close' event if it is\ncreated with the emitClose option.
The 'data' event is emitted whenever the stream is relinquishing ownership of\na chunk of data to a consumer. This may occur whenever the stream is switched\nin flowing mode by calling readable.pipe(), readable.resume(), or by\nattaching a listener callback to the 'data' event. The 'data' event will\nalso be emitted whenever the readable.read() method is called and a chunk of\ndata is available to be returned.
Attaching a 'data' event listener to a stream that has not been explicitly\npaused will switch the stream into flowing mode. Data will then be passed as\nsoon as it is available.
The listener callback will be passed the chunk of data as a string if a default\nencoding has been specified for the stream using the\nreadable.setEncoding() method; otherwise the data will be passed as a\nBuffer.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n});\nThe 'end' event is emitted when there is no more data to be consumed from\nthe stream.
The 'end' event will not be emitted unless the data is completely\nconsumed. This can be accomplished by switching the stream into flowing mode,\nor by calling stream.read() repeatedly until all data has been\nconsumed.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n});\nreadable.on('end', () => {\n console.log('There will be no more data.');\n});\nThe 'error' event may be emitted by a Readable implementation at any time.\nTypically, this may occur if the underlying stream is unable to generate data\ndue to an underlying internal failure, or when a stream implementation attempts\nto push an invalid chunk of data.
The listener callback will be passed a single Error object.
The 'readable' event is emitted when there is data available to be read from\nthe stream. In some cases, attaching a listener for the 'readable' event will\ncause some amount of data to be read into an internal buffer.
const readable = getReadableStreamSomehow();\nreadable.on('readable', function() {\n // there is some data to read now\n let data;\n\n while (data = this.read()) {\n console.log(data);\n }\n});\nThe 'readable' event will also be emitted once the end of the stream data\nhas been reached but before the 'end' event is emitted.
Effectively, the 'readable' event indicates that the stream has new\ninformation: either new data is available or the end of the stream has been\nreached. In the former case, stream.read() will return the\navailable data. In the latter case, stream.read() will return\nnull. For instance, in the following example, foo.txt is an empty file:
const fs = require('fs');\nconst rr = fs.createReadStream('foo.txt');\nrr.on('readable', () => {\n console.log(`readable: ${rr.read()}`);\n});\nrr.on('end', () => {\n console.log('end');\n});\nThe output of running this script is:
\n$ node test.js\nreadable: null\nend\nIn general, the readable.pipe() and 'data' event mechanisms are easier to\nunderstand than the 'readable' event. However, handling 'readable' might\nresult in increased throughput.
If both 'readable' and 'data' are used at the same time, 'readable'\ntakes precedence in controlling the flow, i.e. 'data' will be emitted\nonly when stream.read() is called. The\nreadableFlowing property would become false.\nIf there are 'data' listeners when 'readable' is removed, the stream\nwill start flowing, i.e. 'data' events will be emitted without calling\n.resume().
Destroy the stream, and emit 'error' and 'close'. After this call, the\nreadable stream will release any internal resources and subsequent calls\nto push() will be ignored.\nImplementors should not override this method, but instead implement\nreadable._destroy().
The readable.isPaused() method returns the current operating state of the\nReadable. This is used primarily by the mechanism that underlies the\nreadable.pipe() method. In most typical cases, there will be no reason to\nuse this method directly.
const readable = new stream.Readable();\n\nreadable.isPaused(); // === false\nreadable.pause();\nreadable.isPaused(); // === true\nreadable.resume();\nreadable.isPaused(); // === false\nThe readable.pause() method will cause a stream in flowing mode to stop\nemitting 'data' events, switching out of flowing mode. Any data that\nbecomes available will remain in the internal buffer.
const readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log(`Received ${chunk.length} bytes of data.`);\n readable.pause();\n console.log('There will be no additional data for 1 second.');\n setTimeout(() => {\n console.log('Now data will start flowing again.');\n readable.resume();\n }, 1000);\n});\nThe readable.pause() method has no effect if there is a 'readable'\nevent listener.
The readable.pipe() method attaches a Writable stream to the readable,\ncausing it to switch automatically into flowing mode and push all of its data\nto the attached Writable. The flow of data will be automatically managed\nso that the destination Writable stream is not overwhelmed by a faster\nReadable stream.
The following example pipes all of the data from the readable into a file\nnamed file.txt:
const fs = require('fs');\nconst readable = getReadableStreamSomehow();\nconst writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt'\nreadable.pipe(writable);\nIt is possible to attach multiple Writable streams to a single Readable\nstream.
The readable.pipe() method returns a reference to the destination stream\nmaking it possible to set up chains of piped streams:
const fs = require('fs');\nconst r = fs.createReadStream('file.txt');\nconst z = zlib.createGzip();\nconst w = fs.createWriteStream('file.txt.gz');\nr.pipe(z).pipe(w);\nBy default, stream.end() is called on the destination Writable\nstream when the source Readable stream emits 'end', so that the\ndestination is no longer writable. To disable this default behavior, the end\noption can be passed as false, causing the destination stream to remain open:
reader.pipe(writer, { end: false });\nreader.on('end', () => {\n writer.end('Goodbye\\n');\n});\nOne important caveat is that if the Readable stream emits an error during\nprocessing, the Writable destination is not closed automatically. If an\nerror occurs, it will be necessary to manually close each stream in order\nto prevent memory leaks.
The process.stderr and process.stdout Writable streams are never\nclosed until the Node.js process exits, regardless of the specified options.
The readable.read() method pulls some data out of the internal buffer and\nreturns it. If no data available to be read, null is returned. By default,\nthe data will be returned as a Buffer object unless an encoding has been\nspecified using the readable.setEncoding() method or the stream is operating\nin object mode.
The optional size argument specifies a specific number of bytes to read. If\nsize bytes are not available to be read, null will be returned unless\nthe stream has ended, in which case all of the data remaining in the internal\nbuffer will be returned.
If the size argument is not specified, all of the data contained in the\ninternal buffer will be returned.
The size argument must be less than or equal to 1 GB.
The readable.read() method should only be called on Readable streams\noperating in paused mode. In flowing mode, readable.read() is called\nautomatically until the internal buffer is fully drained.
const readable = getReadableStreamSomehow();\nreadable.on('readable', () => {\n let chunk;\n while (null !== (chunk = readable.read())) {\n console.log(`Received ${chunk.length} bytes of data.`);\n }\n});\nNote that the while loop is necessary when processing data with\nreadable.read(). Only after readable.read() returns null,\n'readable' will be emitted.
A Readable stream in object mode will always return a single item from\na call to readable.read(size), regardless of the value of the\nsize argument.
If the readable.read() method returns a chunk of data, a 'data' event will\nalso be emitted.
Calling stream.read([size]) after the 'end' event has\nbeen emitted will return null. No runtime error will be raised.
The readable.resume() method causes an explicitly paused Readable stream to\nresume emitting 'data' events, switching the stream into flowing mode.
The readable.resume() method can be used to fully consume the data from a\nstream without actually processing any of that data:
getReadableStreamSomehow()\n .resume()\n .on('end', () => {\n console.log('Reached the end, but did not read anything.');\n });\nThe readable.resume() method has no effect if there is a 'readable'\nevent listener.
The readable.setEncoding() method sets the character encoding for\ndata read from the Readable stream.
By default, no encoding is assigned and stream data will be returned as\nBuffer objects. Setting an encoding causes the stream data\nto be returned as strings of the specified encoding rather than as Buffer\nobjects. For instance, calling readable.setEncoding('utf8') will cause the\noutput data to be interpreted as UTF-8 data, and passed as strings. Calling\nreadable.setEncoding('hex') will cause the data to be encoded in hexadecimal\nstring format.
The Readable stream will properly handle multi-byte characters delivered\nthrough the stream that would otherwise become improperly decoded if simply\npulled from the stream as Buffer objects.
const readable = getReadableStreamSomehow();\nreadable.setEncoding('utf8');\nreadable.on('data', (chunk) => {\n assert.equal(typeof chunk, 'string');\n console.log('Got %d characters of string data:', chunk.length);\n});\nThe readable.unpipe() method detaches a Writable stream previously attached\nusing the stream.pipe() method.
If the destination is not specified, then all pipes are detached.
If the destination is specified, but no pipe is set up for it, then\nthe method does nothing.
const fs = require('fs');\nconst readable = getReadableStreamSomehow();\nconst writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt',\n// but only for the first second\nreadable.pipe(writable);\nsetTimeout(() => {\n console.log('Stop writing to file.txt.');\n readable.unpipe(writable);\n console.log('Manually close the file stream.');\n writable.end();\n}, 1000);\nThe readable.unshift() method pushes a chunk of data back into the internal\nbuffer. This is useful in certain situations where a stream is being consumed by\ncode that needs to \"un-consume\" some amount of data that it has optimistically\npulled out of the source, so that the data can be passed on to some other party.
The stream.unshift(chunk) method cannot be called after the 'end' event\nhas been emitted or a runtime error will be thrown.
Developers using stream.unshift() often should consider switching to\nuse of a Transform stream instead. See the API for Stream Implementers\nsection for more information.
// Pull off a header delimited by \\n\\n\n// use unshift() if we get too much\n// Call the callback with (error, header, stream)\nconst { StringDecoder } = require('string_decoder');\nfunction parseHeader(stream, callback) {\n stream.on('error', callback);\n stream.on('readable', onReadable);\n const decoder = new StringDecoder('utf8');\n let header = '';\n function onReadable() {\n let chunk;\n while (null !== (chunk = stream.read())) {\n const str = decoder.write(chunk);\n if (str.match(/\\n\\n/)) {\n // found the header boundary\n const split = str.split(/\\n\\n/);\n header += split.shift();\n const remaining = split.join('\\n\\n');\n const buf = Buffer.from(remaining, 'utf8');\n stream.removeListener('error', callback);\n // remove the 'readable' listener before unshifting\n stream.removeListener('readable', onReadable);\n if (buf.length)\n stream.unshift(buf);\n // now the body of the message can be read from the stream.\n callback(null, header, stream);\n } else {\n // still reading the header.\n header += str;\n }\n }\n }\n}\nUnlike stream.push(chunk), stream.unshift(chunk) will not\nend the reading process by resetting the internal reading state of the stream.\nThis can cause unexpected results if readable.unshift() is called during a\nread (i.e. from within a stream._read() implementation on a\ncustom stream). Following the call to readable.unshift() with an immediate\nstream.push('') will reset the reading state appropriately,\nhowever it is best to simply avoid calling readable.unshift() while in the\nprocess of performing a read.
Prior to Node.js 0.10, streams did not implement the entire stream module API\nas it is currently defined. (See Compatibility for more information.)
When using an older Node.js library that emits 'data' events and has a\nstream.pause() method that is advisory only, the\nreadable.wrap() method can be used to create a Readable stream that uses\nthe old stream as its data source.
It will rarely be necessary to use readable.wrap() but the method has been\nprovided as a convenience for interacting with older Node.js applications and\nlibraries.
const { OldReader } = require('./old-api-module.js');\nconst { Readable } = require('stream');\nconst oreader = new OldReader();\nconst myReader = new Readable().wrap(oreader);\n\nmyReader.on('readable', () => {\n myReader.read(); // etc.\n});\nconst fs = require('fs');\n\nasync function print(readable) {\n readable.setEncoding('utf8');\n let data = '';\n for await (const k of readable) {\n data += k;\n }\n console.log(data);\n}\n\nprint(fs.createReadStream('file')).catch(console.log);\nIf the loop terminates with a break or a throw, the stream will be\ndestroyed. In other terms, iterating over a stream will consume the stream\nfully. The stream will be read in chunks of size equal to the highWaterMark\noption. In the code example above, data will be in a single chunk if the file\nhas less then 64kb of data because no highWaterMark option is provided to\nfs.createReadStream().
Is true if it is safe to call [readable.read()][].
This property reflects the current state of a Readable stream as described\nin the Stream Three States section.
Returns the value of highWaterMark passed when constructing this\nReadable.
This property contains the number of bytes (or objects) in the queue\nready to be read. The value provides introspection data regarding\nthe status of the highWaterMark.
Duplex streams are streams that implement both the Readable and\nWritable interfaces.
Examples of Duplex streams include:
Transform streams are Duplex streams where the output is in some way\nrelated to the input. Like all Duplex streams, Transform streams\nimplement both the Readable and Writable interfaces.
Examples of Transform streams include:
Destroy the stream, and emit 'error'. After this call, the\ntransform stream would release any internal resources.\nImplementors should not override this method, but instead implement\nreadable._destroy().\nThe default implementation of _destroy() for Transform also emit 'close'.
A function to get notified when a stream is no longer readable, writable\nor has experienced an error or a premature close event.
\nconst { finished } = require('stream');\n\nconst rs = fs.createReadStream('archive.tar');\n\nfinished(rs, (err) => {\n if (err) {\n console.error('Stream failed.', err);\n } else {\n console.log('Stream is done reading.');\n }\n});\n\nrs.resume(); // drain the stream\nEspecially useful in error handling scenarios where a stream is destroyed\nprematurely (like an aborted HTTP request), and will not emit 'end'\nor 'finish'.
The finished API is promisify-able as well;
const finished = util.promisify(stream.finished);\n\nconst rs = fs.createReadStream('archive.tar');\n\nasync function run() {\n await finished(rs);\n console.log('Stream is done reading.');\n}\n\nrun().catch(console.error);\nrs.resume(); // drain the stream\nA module method to pipe between streams forwarding errors and properly cleaning\nup and provide a callback when the pipeline is complete.
\nconst { pipeline } = require('stream');\nconst fs = require('fs');\nconst zlib = require('zlib');\n\n// Use the pipeline API to easily pipe a series of streams\n// together and get notified when the pipeline is fully done.\n\n// A pipeline to gzip a potentially huge tar file efficiently:\n\npipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz'),\n (err) => {\n if (err) {\n console.error('Pipeline failed.', err);\n } else {\n console.log('Pipeline succeeded.');\n }\n }\n);\nThe pipeline API is promisify-able as well:
const pipeline = util.promisify(stream.pipeline);\n\nasync function run() {\n await pipeline(\n fs.createReadStream('archive.tar'),\n zlib.createGzip(),\n fs.createWriteStream('archive.tar.gz')\n );\n console.log('Pipeline succeeded.');\n}\n\nrun().catch(console.error);\nA utility method for creating Readable Streams out of iterators.
\nconst { Readable } = require('stream');\n\nasync function * generate() {\n yield 'hello';\n yield 'streams';\n}\n\nconst readable = Readable.from(generate());\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\nThe stream module API has been designed to make it possible to easily\nimplement streams using JavaScript's prototypal inheritance model.
First, a stream developer would declare a new JavaScript class that extends one\nof the four basic stream classes (stream.Writable, stream.Readable,\nstream.Duplex, or stream.Transform), making sure they call the appropriate\nparent class constructor:
const { Writable } = require('stream');\n\nclass MyWritable extends Writable {\n constructor(options) {\n super(options);\n // ...\n }\n}\nThe new stream class must then implement one or more specific methods, depending\non the type of stream being created, as detailed in the chart below:
\n| Use-case | \nClass | \nMethod(s) to implement | \n
|---|---|---|
| Reading only | \nReadable | \n_read | \n
| Writing only | \nWritable | \n_write, _writev, _final | \n
| Reading and writing | \nDuplex | \n_read, _write, _writev, _final | \n
| Operate on written data, then read the result | \nTransform | \n_transform, _flush, _final | \n
The implementation code for a stream should never call the \"public\" methods\nof a stream that are intended for use by consumers (as described in the\nAPI for Stream Consumers section). Doing so may lead to adverse side effects\nin application code consuming the stream.
", "miscs": [ { "textRaw": "Simplified Construction", "name": "simplified_construction", "meta": { "added": [ "v1.2.0" ], "changes": [] }, "desc": "For many simple cases, it is possible to construct a stream without relying on\ninheritance. This can be accomplished by directly creating instances of the\nstream.Writable, stream.Readable, stream.Duplex or stream.Transform\nobjects and passing appropriate methods as constructor options.
const { Writable } = require('stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\n }\n});\nThe stream.Writable class is extended to implement a Writable stream.
Custom Writable streams must call the new stream.Writable([options])\nconstructor and implement the writable._write() method. The\nwritable._writev() method may also be implemented.
const { Writable } = require('stream');\n\nclass MyWritable extends Writable {\n constructor(options) {\n // Calls the stream.Writable() constructor\n super(options);\n // ...\n }\n}\nOr, when using pre-ES6 style constructors:
\nconst { Writable } = require('stream');\nconst util = require('util');\n\nfunction MyWritable(options) {\n if (!(this instanceof MyWritable))\n return new MyWritable(options);\n Writable.call(this, options);\n}\nutil.inherits(MyWritable, Writable);\nOr, using the Simplified Constructor approach:
\nconst { Writable } = require('stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n // ...\n },\n writev(chunks, callback) {\n // ...\n }\n});\nAll Writable stream implementations must provide a\nwritable._write() method to send data to the underlying\nresource.
Transform streams provide their own implementation of the\nwritable._write().
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Writable class\nmethods only.
The callback method must be called to signal either that the write completed\nsuccessfully or failed with an error. The first argument passed to the\ncallback must be the Error object if the call failed or null if the\nwrite succeeded.
All calls to writable.write() that occur between the time writable._write()\nis called and the callback is called will cause the written data to be\nbuffered. When the callback is invoked, the stream might emit a 'drain'\nevent. If a stream implementation is capable of processing multiple chunks of\ndata at once, the writable._writev() method should be implemented.
If the decodeStrings property is explicitly set to false in the constructor\noptions, then chunk will remain the same object that is passed to .write(),\nand may be a string rather than a Buffer. This is to support implementations\nthat have an optimized handling for certain string data encodings. In that case,\nthe encoding argument will indicate the character encoding of the string.\nOtherwise, the encoding argument can be safely ignored.
The writable._write() method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Writable class\nmethods only.
The writable._writev() method may be implemented in addition to\nwritable._write() in stream implementations that are capable of processing\nmultiple chunks of data at once. If implemented, the method will be called with\nall chunks of data currently buffered in the write queue.
The writable._writev() method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
The _destroy() method is called by writable.destroy().\nIt can be overridden by child classes but it must not be called directly.
The _final() method must not be called directly. It may be implemented\nby child classes, and if so, will be called by the internal Writable\nclass methods only.
This optional function will be called before the stream closes, delaying the\n'finish' event until callback is called. This is useful to close resources\nor write buffered data before a stream ends.
It is recommended that errors occurring during the processing of the\nwritable._write() and writable._writev() methods are reported by invoking\nthe callback and passing the error as the first argument. This will cause an\n'error' event to be emitted by the Writable. Throwing an Error from within\nwritable._write() can result in unexpected and inconsistent behavior depending\non how the stream is being used. Using the callback ensures consistent and\npredictable handling of errors.
If a Readable stream pipes into a Writable stream when Writable emits an\nerror, the Readable stream will be unpiped.
const { Writable } = require('stream');\n\nconst myWritable = new Writable({\n write(chunk, encoding, callback) {\n if (chunk.toString().indexOf('a') >= 0) {\n callback(new Error('chunk is invalid'));\n } else {\n callback();\n }\n }\n});\nThe following illustrates a rather simplistic (and somewhat pointless) custom\nWritable stream implementation. While this specific Writable stream instance\nis not of any real particular usefulness, the example illustrates each of the\nrequired elements of a custom Writable stream instance:
const { Writable } = require('stream');\n\nclass MyWritable extends Writable {\n _write(chunk, encoding, callback) {\n if (chunk.toString().indexOf('a') >= 0) {\n callback(new Error('chunk is invalid'));\n } else {\n callback();\n }\n }\n}\nDecoding buffers is a common task, for instance, when using transformers whose\ninput is a string. This is not a trivial process when using multi-byte\ncharacters encoding, such as UTF-8. The following example shows how to decode\nmulti-byte strings using StringDecoder and Writable.
const { Writable } = require('stream');\nconst { StringDecoder } = require('string_decoder');\n\nclass StringWritable extends Writable {\n constructor(options) {\n super(options);\n this._decoder = new StringDecoder(options && options.defaultEncoding);\n this.data = '';\n }\n _write(chunk, encoding, callback) {\n if (encoding === 'buffer') {\n chunk = this._decoder.write(chunk);\n }\n this.data += chunk;\n callback();\n }\n _final(callback) {\n this.data += this._decoder.end();\n callback();\n }\n}\n\nconst euro = [[0xE2, 0x82], [0xAC]].map(Buffer.from);\nconst w = new StringWritable();\n\nw.write('currency: ');\nw.write(euro[0]);\nw.end(euro[1]);\n\nconsole.log(w.data); // currency: €\nThe stream.Readable class is extended to implement a Readable stream.
Custom Readable streams must call the new stream.Readable([options])\nconstructor and implement the readable._read() method.
const { Readable } = require('stream');\n\nclass MyReadable extends Readable {\n constructor(options) {\n // Calls the stream.Readable(options) constructor\n super(options);\n // ...\n }\n}\nOr, when using pre-ES6 style constructors:
\nconst { Readable } = require('stream');\nconst util = require('util');\n\nfunction MyReadable(options) {\n if (!(this instanceof MyReadable))\n return new MyReadable(options);\n Readable.call(this, options);\n}\nutil.inherits(MyReadable, Readable);\nOr, using the Simplified Constructor approach:
\nconst { Readable } = require('stream');\n\nconst myReadable = new Readable({\n read(size) {\n // ...\n }\n});\nThis function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable class\nmethods only.
All Readable stream implementations must provide an implementation of the\nreadable._read() method to fetch data from the underlying resource.
When readable._read() is called, if data is available from the resource, the\nimplementation should begin pushing that data into the read queue using the\nthis.push(dataChunk) method. _read() should continue reading\nfrom the resource and pushing data until readable.push() returns false. Only\nwhen _read() is called again after it has stopped should it resume pushing\nadditional data onto the queue.
Once the readable._read() method has been called, it will not be called again\nuntil the readable.push() method is called. readable._read()\nis guaranteed to be called only once within a synchronous execution, i.e. a\nmicrotick.
The size argument is advisory. For implementations where a \"read\" is a\nsingle operation that returns data can use the size argument to determine how\nmuch data to fetch. Other implementations may ignore this argument and simply\nprovide data whenever it becomes available. There is no need to \"wait\" until\nsize bytes are available before calling stream.push(chunk).
The readable._read() method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
The _destroy() method is called by readable.destroy().\nIt can be overridden by child classes but it must not be called directly.
When chunk is a Buffer, Uint8Array or string, the chunk of data will\nbe added to the internal queue for users of the stream to consume.\nPassing chunk as null signals the end of the stream (EOF), after which no\nmore data can be written.
When the Readable is operating in paused mode, the data added with\nreadable.push() can be read out by calling the\nreadable.read() method when the 'readable' event is\nemitted.
When the Readable is operating in flowing mode, the data added with\nreadable.push() will be delivered by emitting a 'data' event.
The readable.push() method is designed to be as flexible as possible. For\nexample, when wrapping a lower-level source that provides some form of\npause/resume mechanism, and a data callback, the low-level source can be wrapped\nby the custom Readable instance:
// source is an object with readStop() and readStart() methods,\n// and an `ondata` member that gets called when it has data, and\n// an `onend` member that gets called when the data is over.\n\nclass SourceWrapper extends Readable {\n constructor(options) {\n super(options);\n\n this._source = getLowlevelSourceObject();\n\n // Every time there's data, push it into the internal buffer.\n this._source.ondata = (chunk) => {\n // if push() returns false, then stop reading from source\n if (!this.push(chunk))\n this._source.readStop();\n };\n\n // When the source ends, push the EOF-signaling `null` chunk\n this._source.onend = () => {\n this.push(null);\n };\n }\n // _read will be called when the stream wants to pull more data in\n // the advisory size argument is ignored in this case.\n _read(size) {\n this._source.readStart();\n }\n}\nThe readable.push() method is intended be called only by Readable\nimplementers, and only from within the readable._read() method.
For streams not operating in object mode, if the chunk parameter of\nreadable.push() is undefined, it will be treated as empty string or\nbuffer. See readable.push('') for more information.
It is recommended that errors occurring during the processing of the\nreadable._read() method are emitted using the 'error' event rather than\nbeing thrown. Throwing an Error from within readable._read() can result in\nunexpected and inconsistent behavior depending on whether the stream is\noperating in flowing or paused mode. Using the 'error' event ensures\nconsistent and predictable handling of errors.
const { Readable } = require('stream');\n\nconst myReadable = new Readable({\n read(size) {\n if (checkSomeErrorCondition()) {\n process.nextTick(() => this.emit('error', err));\n return;\n }\n // do some work\n }\n});\nThe following is a basic example of a Readable stream that emits the numerals\nfrom 1 to 1,000,000 in ascending order, and then ends.
const { Readable } = require('stream');\n\nclass Counter extends Readable {\n constructor(opt) {\n super(opt);\n this._max = 1000000;\n this._index = 1;\n }\n\n _read() {\n const i = this._index++;\n if (i > this._max)\n this.push(null);\n else {\n const str = String(i);\n const buf = Buffer.from(str, 'ascii');\n this.push(buf);\n }\n }\n}\nA Duplex stream is one that implements both Readable and\nWritable, such as a TCP socket connection.
Because JavaScript does not have support for multiple inheritance, the\nstream.Duplex class is extended to implement a Duplex stream (as opposed\nto extending the stream.Readable and stream.Writable classes).
The stream.Duplex class prototypically inherits from stream.Readable and\nparasitically from stream.Writable, but instanceof will work properly for\nboth base classes due to overriding Symbol.hasInstance on\nstream.Writable.
Custom Duplex streams must call the new stream.Duplex([options])\nconstructor and implement both the readable._read() and\nwritable._write() methods.
const { Duplex } = require('stream');\n\nclass MyDuplex extends Duplex {\n constructor(options) {\n super(options);\n // ...\n }\n}\nOr, when using pre-ES6 style constructors:
\nconst { Duplex } = require('stream');\nconst util = require('util');\n\nfunction MyDuplex(options) {\n if (!(this instanceof MyDuplex))\n return new MyDuplex(options);\n Duplex.call(this, options);\n}\nutil.inherits(MyDuplex, Duplex);\nOr, using the Simplified Constructor approach:
\nconst { Duplex } = require('stream');\n\nconst myDuplex = new Duplex({\n read(size) {\n // ...\n },\n write(chunk, encoding, callback) {\n // ...\n }\n});\nThe following illustrates a simple example of a Duplex stream that wraps a\nhypothetical lower-level source object to which data can be written, and\nfrom which data can be read, albeit using an API that is not compatible with\nNode.js streams.\nThe following illustrates a simple example of a Duplex stream that buffers\nincoming written data via the Writable interface that is read back out\nvia the Readable interface.
const { Duplex } = require('stream');\nconst kSource = Symbol('source');\n\nclass MyDuplex extends Duplex {\n constructor(source, options) {\n super(options);\n this[kSource] = source;\n }\n\n _write(chunk, encoding, callback) {\n // The underlying source only deals with strings\n if (Buffer.isBuffer(chunk))\n chunk = chunk.toString();\n this[kSource].writeSomeData(chunk);\n callback();\n }\n\n _read(size) {\n this[kSource].fetchSomeData(size, (data, encoding) => {\n this.push(Buffer.from(data, encoding));\n });\n }\n}\nThe most important aspect of a Duplex stream is that the Readable and\nWritable sides operate independently of one another despite co-existing within\na single object instance.
For Duplex streams, objectMode can be set exclusively for either the\nReadable or Writable side using the readableObjectMode and\nwritableObjectMode options respectively.
In the following example, for instance, a new Transform stream (which is a\ntype of Duplex stream) is created that has an object mode Writable side\nthat accepts JavaScript numbers that are converted to hexadecimal strings on\nthe Readable side.
const { Transform } = require('stream');\n\n// All Transform streams are also Duplex Streams\nconst myTransform = new Transform({\n writableObjectMode: true,\n\n transform(chunk, encoding, callback) {\n // Coerce the chunk to a number if necessary\n chunk |= 0;\n\n // Transform the chunk into something else.\n const data = chunk.toString(16);\n\n // Push the data onto the readable queue.\n callback(null, '0'.repeat(data.length % 2) + data);\n }\n});\n\nmyTransform.setEncoding('ascii');\nmyTransform.on('data', (chunk) => console.log(chunk));\n\nmyTransform.write(1);\n// Prints: 01\nmyTransform.write(10);\n// Prints: 0a\nmyTransform.write(100);\n// Prints: 64\nA Transform stream is a Duplex stream where the output is computed\nin some way from the input. Examples include zlib streams or crypto\nstreams that compress, encrypt, or decrypt data.
There is no requirement that the output be the same size as the input, the same\nnumber of chunks, or arrive at the same time. For example, a Hash stream will\nonly ever have a single chunk of output which is provided when the input is\nended. A zlib stream will produce output that is either much smaller or much\nlarger than its input.
The stream.Transform class is extended to implement a Transform stream.
The stream.Transform class prototypically inherits from stream.Duplex and\nimplements its own versions of the writable._write() and readable._read()\nmethods. Custom Transform implementations must implement the\ntransform._transform() method and may also implement\nthe transform._flush() method.
Care must be taken when using Transform streams in that data written to the\nstream can cause the Writable side of the stream to become paused if the\noutput on the Readable side is not consumed.
const { Transform } = require('stream');\n\nclass MyTransform extends Transform {\n constructor(options) {\n super(options);\n // ...\n }\n}\nOr, when using pre-ES6 style constructors:
\nconst { Transform } = require('stream');\nconst util = require('util');\n\nfunction MyTransform(options) {\n if (!(this instanceof MyTransform))\n return new MyTransform(options);\n Transform.call(this, options);\n}\nutil.inherits(MyTransform, Transform);\nOr, using the Simplified Constructor approach:
\nconst { Transform } = require('stream');\n\nconst myTransform = new Transform({\n transform(chunk, encoding, callback) {\n // ...\n }\n});\nThe 'finish' and 'end' events are from the stream.Writable\nand stream.Readable classes, respectively. The 'finish' event is emitted\nafter stream.end() is called and all chunks have been processed\nby stream._transform(). The 'end' event is emitted\nafter all data has been output, which occurs after the callback in\ntransform._flush() has been called.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable class\nmethods only.
In some cases, a transform operation may need to emit an additional bit of\ndata at the end of the stream. For example, a zlib compression stream will\nstore an amount of internal state used to optimally compress the output. When\nthe stream ends, however, that additional data needs to be flushed so that the\ncompressed data will be complete.
Custom Transform implementations may implement the transform._flush()\nmethod. This will be called when there is no more written data to be consumed,\nbut before the 'end' event is emitted signaling the end of the\nReadable stream.
Within the transform._flush() implementation, the readable.push() method\nmay be called zero or more times, as appropriate. The callback function must\nbe called when the flush operation is complete.
The transform._flush() method is prefixed with an underscore because it is\ninternal to the class that defines it, and should never be called directly by\nuser programs.
This function MUST NOT be called by application code directly. It should be\nimplemented by child classes, and called by the internal Readable class\nmethods only.
All Transform stream implementations must provide a _transform()\nmethod to accept input and produce output. The transform._transform()\nimplementation handles the bytes being written, computes an output, then passes\nthat output off to the readable portion using the readable.push() method.
The transform.push() method may be called zero or more times to generate\noutput from a single input chunk, depending on how much is to be output\nas a result of the chunk.
It is possible that no output is generated from any given chunk of input data.
\nThe callback function must be called only when the current chunk is completely\nconsumed. The first argument passed to the callback must be an Error object\nif an error occurred while processing the input or null otherwise. If a second\nargument is passed to the callback, it will be forwarded on to the\nreadable.push() method. In other words, the following are equivalent:
transform.prototype._transform = function(data, encoding, callback) {\n this.push(data);\n callback();\n};\n\ntransform.prototype._transform = function(data, encoding, callback) {\n callback(null, data);\n};\nThe transform._transform() method is prefixed with an underscore because it\nis internal to the class that defines it, and should never be called directly by\nuser programs.
transform._transform() is never called in parallel; streams implement a\nqueue mechanism, and to receive the next chunk, callback must be\ncalled, either synchronously or asynchronously.
The stream.PassThrough class is a trivial implementation of a Transform\nstream that simply passes the input bytes across to the output. Its purpose is\nprimarily for examples and testing, but there are some use cases where\nstream.PassThrough is useful as a building block for novel sorts of streams.
With the support of async generators and iterators in JavaScript, async\ngenerators are effectively a first-class language-level stream construct at\nthis point.
\nSome common interop cases of using Node.js streams with async generators\nand async iterators are provided below.
", "modules": [ { "textRaw": "Consuming Readable Streams with Async Iterators", "name": "consuming_readable_streams_with_async_iterators", "desc": "(async function() {\n for await (const chunk of readable) {\n console.log(chunk);\n }\n})();\nWe can construct a Node.js Readable Stream from an asynchronous generator\nusing the Readable.from utility method:
const { Readable } = require('stream');\n\nasync function * generate() {\n yield 'a';\n yield 'b';\n yield 'c';\n}\n\nconst readable = Readable.from(generate());\n\nreadable.on('data', (chunk) => {\n console.log(chunk);\n});\nIn the scenario of writing to a writeable stream from an async iterator,\nit is important to ensure the correct handling of backpressure and errors.
\nconst { once } = require('events');\n\nconst writeable = fs.createWriteStream('./file');\n\n(async function() {\n for await (const chunk of iterator) {\n // Handle backpressure on write\n if (!writeable.write(value))\n await once(writeable, 'drain');\n }\n writeable.end();\n // Ensure completion without errors\n await once(writeable, 'finish');\n})();\nIn the above, errors on the write stream would be caught and thrown by the two\nonce listeners, since once will also handle 'error' events.
Alternatively the readable stream could be wrapped with Readable.from and\nthen piped via .pipe:
const { once } = require('events');\n\nconst writeable = fs.createWriteStream('./file');\n\n(async function() {\n const readable = Readable.from(iterator);\n readable.pipe(writeable);\n // Ensure completion without errors\n await once(writeable, 'finish');\n})();\nPrior to Node.js 0.10, the Readable stream interface was simpler, but also\nless powerful and less useful.
stream.read() method,\n'data' events would begin emitting immediately. Applications that\nwould need to perform some amount of work to decide how to handle data\nwere required to store read data into buffers so the data would not be lost.stream.pause() method was advisory, rather than\nguaranteed. This meant that it was still necessary to be prepared to receive\n'data' events even when the stream was in a paused state.In Node.js 0.10, the Readable class was added. For backward\ncompatibility with older Node.js programs, Readable streams switch into\n\"flowing mode\" when a 'data' event handler is added, or when the\nstream.resume() method is called. The effect is that, even\nwhen not using the new stream.read() method and\n'readable' event, it is no longer necessary to worry about losing\n'data' chunks.
While most applications will continue to function normally, this introduces an\nedge case in the following conditions:
\n'data' event listener is added.stream.resume() method is never called.For example, consider the following code:
\n// WARNING! BROKEN!\nnet.createServer((socket) => {\n\n // we add an 'end' listener, but never consume the data\n socket.on('end', () => {\n // It will never get here.\n socket.end('The message was received but was not processed.\\n');\n });\n\n}).listen(1337);\nPrior to Node.js 0.10, the incoming message data would be simply discarded.\nHowever, in Node.js 0.10 and beyond, the socket remains paused forever.
\nThe workaround in this situation is to call the\nstream.resume() method to begin the flow of data:
// Workaround\nnet.createServer((socket) => {\n socket.on('end', () => {\n socket.end('The message was received but was not processed.\\n');\n });\n\n // start the flow of data, discarding it.\n socket.resume();\n}).listen(1337);\nIn addition to new Readable streams switching into flowing mode,\npre-0.10 style streams can be wrapped in a Readable class using the\nreadable.wrap() method.
There are some cases where it is necessary to trigger a refresh of the\nunderlying readable stream mechanisms, without actually consuming any\ndata. In such cases, it is possible to call readable.read(0), which will\nalways return null.
If the internal read buffer is below the highWaterMark, and the\nstream is not currently reading, then calling stream.read(0) will trigger\na low-level stream._read() call.
While most applications will almost never need to do this, there are\nsituations within Node.js where this is done, particularly in the\nReadable stream class internals.
Use of readable.push('') is not recommended.
Pushing a zero-byte string, Buffer or Uint8Array to a stream that is not in\nobject mode has an interesting side effect. Because it is a call to\nreadable.push(), the call will end the reading process.\nHowever, because the argument is an empty string, no data is added to the\nreadable buffer so there is nothing for a user to consume.
The use of readable.setEncoding() will change the behavior of how the\nhighWaterMark operates in non-object mode.
Typically, the size of the current buffer is measured against the\nhighWaterMark in bytes. However, after setEncoding() is called, the\ncomparison function will begin to measure the buffer's size in characters.
This is not a problem in common cases with latin1 or ascii. But it is\nadvised to be mindful about this behavior when working with strings that could\ncontain multi-byte characters.
The string_decoder module provides an API for decoding Buffer objects into\nstrings in a manner that preserves encoded multi-byte UTF-8 and UTF-16\ncharacters. It can be accessed using:
const { StringDecoder } = require('string_decoder');\nThe following example shows the basic use of the StringDecoder class.
const { StringDecoder } = require('string_decoder');\nconst decoder = new StringDecoder('utf8');\n\nconst cent = Buffer.from([0xC2, 0xA2]);\nconsole.log(decoder.write(cent));\n\nconst euro = Buffer.from([0xE2, 0x82, 0xAC]);\nconsole.log(decoder.write(euro));\nWhen a Buffer instance is written to the StringDecoder instance, an\ninternal buffer is used to ensure that the decoded string does not contain\nany incomplete multibyte characters. These are held in the buffer until the\nnext call to stringDecoder.write() or until stringDecoder.end() is called.
In the following example, the three UTF-8 encoded bytes of the European Euro\nsymbol (€) are written over three separate operations:
const { StringDecoder } = require('string_decoder');\nconst decoder = new StringDecoder('utf8');\n\ndecoder.write(Buffer.from([0xE2]));\ndecoder.write(Buffer.from([0x82]));\nconsole.log(decoder.end(Buffer.from([0xAC])));\nReturns any remaining input stored in the internal buffer as a string. Bytes\nrepresenting incomplete UTF-8 and UTF-16 characters will be replaced with\nsubstitution characters appropriate for the character encoding.
\nIf the buffer argument is provided, one final call to stringDecoder.write()\nis performed before returning the remaining input.
Returns a decoded string, ensuring that any incomplete multibyte characters at\nthe end of the Buffer, or TypedArray, or DataView are omitted from the\nreturned string and stored in an internal buffer for the next call to\nstringDecoder.write() or stringDecoder.end().
Creates a new StringDecoder instance.
The timer module exposes a global API for scheduling functions to\nbe called at some future period of time. Because the timer functions are\nglobals, there is no need to call require('timers') to use the API.
The timer functions within Node.js implement a similar API as the timers API\nprovided by Web Browsers but use a different internal implementation that is\nbuilt around the Node.js Event Loop.
", "classes": [ { "textRaw": "Class: Immediate", "type": "class", "name": "Immediate", "desc": "This object is created internally and is returned from setImmediate(). It\ncan be passed to clearImmediate() in order to cancel the scheduled\nactions.
By default, when an immediate is scheduled, the Node.js event loop will continue\nrunning as long as the immediate is active. The Immediate object returned by\nsetImmediate() exports both immediate.ref() and immediate.unref()\nfunctions that can be used to control this default behavior.
When called, requests that the Node.js event loop not exit so long as the\nImmediate is active. Calling immediate.ref() multiple times will have no\neffect.
By default, all Immediate objects are \"ref'ed\", making it normally unnecessary\nto call immediate.ref() unless immediate.unref() had been called previously.
When called, the active Immediate object will not require the Node.js event\nloop to remain active. If there is no other activity keeping the event loop\nrunning, the process may exit before the Immediate object's callback is\ninvoked. Calling immediate.unref() multiple times will have no effect.
This object is created internally and is returned from setTimeout() and\nsetInterval(). It can be passed to either clearTimeout() or\nclearInterval() in order to cancel the scheduled actions.
By default, when a timer is scheduled using either setTimeout() or\nsetInterval(), the Node.js event loop will continue running as long as the\ntimer is active. Each of the Timeout objects returned by these functions\nexport both timeout.ref() and timeout.unref() functions that can be used to\ncontrol this default behavior.
When called, requests that the Node.js event loop not exit so long as the\nTimeout is active. Calling timeout.ref() multiple times will have no effect.
By default, all Timeout objects are \"ref'ed\", making it normally unnecessary\nto call timeout.ref() unless timeout.unref() had been called previously.
Sets the timer's start time to the current time, and reschedules the timer to\ncall its callback at the previously specified duration adjusted to the current\ntime. This is useful for refreshing a timer without allocating a new\nJavaScript object.
\nUsing this on a timer that has already called its callback will reactivate the\ntimer.
" }, { "textRaw": "timeout.unref()", "type": "method", "name": "unref", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Timeout} a reference to `timeout`", "name": "return", "type": "Timeout", "desc": "a reference to `timeout`" }, "params": [] } ], "desc": "When called, the active Timeout object will not require the Node.js event loop\nto remain active. If there is no other activity keeping the event loop running,\nthe process may exit before the Timeout object's callback is invoked. Calling\ntimeout.unref() multiple times will have no effect.
Calling timeout.unref() creates an internal timer that will wake the Node.js\nevent loop. Creating too many of these can adversely impact performance\nof the Node.js application.
A timer in Node.js is an internal construct that calls a given function after\na certain period of time. When a timer's function is called varies depending on\nwhich method was used to create the timer and what other work the Node.js\nevent loop is doing.
", "methods": [ { "textRaw": "setImmediate(callback[, ...args])", "type": "method", "name": "setImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Immediate} for use with [`clearImmediate()`][]", "name": "return", "type": "Immediate", "desc": "for use with [`clearImmediate()`][]" }, "params": [ { "textRaw": "`callback` {Function} The function to call at the end of this turn of [the Node.js Event Loop]", "name": "callback", "type": "Function", "desc": "The function to call at the end of this turn of [the Node.js Event Loop]" }, { "textRaw": "`...args` {any} Optional arguments to pass when the `callback` is called.", "name": "...args", "type": "any", "desc": "Optional arguments to pass when the `callback` is called.", "optional": true } ] } ], "desc": "Schedules the \"immediate\" execution of the callback after I/O events'\ncallbacks.
When multiple calls to setImmediate() are made, the callback functions are\nqueued for execution in the order in which they are created. The entire callback\nqueue is processed every event loop iteration. If an immediate timer is queued\nfrom inside an executing callback, that timer will not be triggered until the\nnext event loop iteration.
If callback is not a function, a TypeError will be thrown.
This method has a custom variant for promises that is available using\nutil.promisify():
const util = require('util');\nconst setImmediatePromise = util.promisify(setImmediate);\n\nsetImmediatePromise('foobar').then((value) => {\n // value === 'foobar' (passing values is optional)\n // This is executed after all I/O callbacks.\n});\n\n// or with async function\nasync function timerExample() {\n console.log('Before I/O callbacks');\n await setImmediatePromise();\n console.log('After I/O callbacks');\n}\ntimerExample();\nSchedules repeated execution of callback every delay milliseconds.
When delay is larger than 2147483647 or less than 1, the delay will be\nset to 1.
If callback is not a function, a TypeError will be thrown.
Schedules execution of a one-time callback after delay milliseconds.
The callback will likely not be invoked in precisely delay milliseconds.\nNode.js makes no guarantees about the exact timing of when callbacks will fire,\nnor of their ordering. The callback will be called as close as possible to the\ntime specified.
When delay is larger than 2147483647 or less than 1, the delay\nwill be set to 1.
If callback is not a function, a TypeError will be thrown.
This method has a custom variant for promises that is available using\nutil.promisify():
const util = require('util');\nconst setTimeoutPromise = util.promisify(setTimeout);\n\nsetTimeoutPromise(40, 'foobar').then((value) => {\n // value === 'foobar' (passing values is optional)\n // This is executed after about 40 milliseconds.\n});\nThe setImmediate(), setInterval(), and setTimeout() methods\neach return objects that represent the scheduled timers. These can be used to\ncancel the timer and prevent it from triggering.
It is not possible to cancel timers that were created using the promisified\nvariants of setImmediate(), setTimeout().
Cancels an Immediate object created by setImmediate().
Cancels a Timeout object created by setInterval().
Cancels a Timeout object created by setTimeout().
The tls module provides an implementation of the Transport Layer Security\n(TLS) and Secure Socket Layer (SSL) protocols that is built on top of OpenSSL.\nThe module can be accessed using:
const tls = require('tls');\nThe TLS/SSL is a public/private key infrastructure (PKI). For most common\ncases, each client and server must have a private key.
\nPrivate keys can be generated in multiple ways. The example below illustrates\nuse of the OpenSSL command-line interface to generate a 2048-bit RSA private\nkey:
\nopenssl genrsa -out ryans-key.pem 2048\nWith TLS/SSL, all servers (and some clients) must have a certificate.\nCertificates are public keys that correspond to a private key, and that are\ndigitally signed either by a Certificate Authority or by the owner of the\nprivate key (such certificates are referred to as \"self-signed\"). The first\nstep to obtaining a certificate is to create a Certificate Signing Request\n(CSR) file.
\nThe OpenSSL command-line interface can be used to generate a CSR for a private\nkey:
\nopenssl req -new -sha256 -key ryans-key.pem -out ryans-csr.pem\nOnce the CSR file is generated, it can either be sent to a Certificate\nAuthority for signing or used to generate a self-signed certificate.
\nCreating a self-signed certificate using the OpenSSL command-line interface\nis illustrated in the example below:
\nopenssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem\nOnce the certificate is generated, it can be used to generate a .pfx or\n.p12 file:
openssl pkcs12 -export -in ryans-cert.pem -inkey ryans-key.pem \\\n -certfile ca-cert.pem -out ryans.pfx\nWhere:
\nin: is the signed certificateinkey: is the associated private keycertfile: is a concatenation of all Certificate Authority (CA) certs into\na single file, e.g. cat ca1-cert.pem ca2-cert.pem > ca-cert.pemThe term \"Forward Secrecy\" or \"Perfect Forward Secrecy\" describes a feature of\nkey-agreement (i.e., key-exchange) methods. That is, the server and client keys\nare used to negotiate new temporary keys that are used specifically and only for\nthe current communication session. Practically, this means that even if the\nserver's private key is compromised, communication can only be decrypted by\neavesdroppers if the attacker manages to obtain the key-pair specifically\ngenerated for the session.
\nPerfect Forward Secrecy is achieved by randomly generating a key pair for\nkey-agreement on every TLS/SSL handshake (in contrast to using the same key for\nall sessions). Methods implementing this technique are called \"ephemeral\".
\nCurrently two methods are commonly used to achieve Perfect Forward Secrecy (note\nthe character \"E\" appended to the traditional abbreviations):
\nEphemeral methods may have some performance drawbacks, because key generation\nis expensive.
\nTo use Perfect Forward Secrecy using DHE with the tls module, it is required\nto generate Diffie-Hellman parameters and specify them with the dhparam\noption to tls.createSecureContext(). The following illustrates the use of\nthe OpenSSL command-line interface to generate such parameters:
openssl dhparam -outform PEM -out dhparam.pem 2048\nIf using Perfect Forward Secrecy using ECDHE, Diffie-Hellman parameters are\nnot required and a default ECDHE curve will be used. The ecdhCurve property\ncan be used when creating a TLS Server to specify the list of names of supported\ncurves to use, see tls.createServer() for more info.
ALPN (Application-Layer Protocol Negotiation Extension) and\nSNI (Server Name Indication) are TLS handshake extensions:
\nThe TLS protocol allows clients to renegotiate certain aspects of the TLS\nsession. Unfortunately, session renegotiation requires a disproportionate amount\nof server-side resources, making it a potential vector for denial-of-service\nattacks.
\nTo mitigate the risk, renegotiation is limited to three times every ten minutes.\nAn 'error' event is emitted on the tls.TLSSocket instance when this\nthreshold is exceeded. The limits are configurable:
tls.CLIENT_RENEG_LIMIT <number> Specifies the number of renegotiation\nrequests. Default: 3.tls.CLIENT_RENEG_WINDOW <number> Specifies the time renegotiation window\nin seconds. Default: 600 (10 minutes).The default renegotiation limits should not be modified without a full\nunderstanding of the implications and risks.
" } ], "modules": [ { "textRaw": "Session Resumption", "name": "session_resumption", "desc": "Establishing a TLS session can be relatively slow. The process can be sped\nup by saving and later reusing the session state. There are several mechanisms\nto do so, discussed here from oldest to newest (and preferred).
\nSession Identifiers Servers generate a unique ID for new connections and\nsend it to the client. Clients and servers save the session state. When\nreconnecting, clients send the ID of their saved session state and if the server\nalso has the state for that ID, it can agree to use it. Otherwise, the server\nwill create a new session. See RFC 2246 for more information, page 23 and\n30.
\nResumption using session identifiers is supported by most web browsers when\nmaking HTTPS requests.
\nFor Node.js, clients must call tls.TLSSocket.getSession() after the\n'secureConnect' event to get the session data, and provide the data to the\nsession option of tls.connect() to reuse the session. Servers must\nimplement handlers for the 'newSession' and 'resumeSession' events\nto save and restore the session data using the session ID as the lookup key to\nreuse sessions. To reuse sessions across load balancers or cluster workers,\nservers must use a shared session cache (such as Redis) in their session\nhandlers.
Session Tickets The servers encrypt the entire session state and send it\nto the client as a \"ticket\". When reconnecting, the state is sent to the server\nin the initial connection. This mechanism avoids the need for server-side\nsession cache. If the server doesn't use the ticket, for any reason (failure\nto decrypt it, it's too old, etc.), it will create a new session and send a new\nticket. See RFC 5077 for more information.
\nResumption using session tickets is becoming commonly supported by many web\nbrowsers when making HTTPS requests.
\nFor Node.js, clients use the same APIs for resumption with session identifiers\nas for resumption with session tickets. For debugging, if\ntls.TLSSocket.getTLSTicket() returns a value, the session data contains a\nticket, otherwise it contains client-side session state.
Single process servers need no specific implementation to use session tickets.\nTo use session tickets across server restarts or load balancers, servers must\nall have the same ticket keys. There are three 16-byte keys internally, but the\ntls API exposes them as a single 48-byte buffer for convenience.
\nIts possible to get the ticket keys by calling server.getTicketKeys() on\none server instance and then distribute them, but it is more reasonable to\nsecurely generate 48 bytes of secure random data and set them with the\nticketKeys option of tls.createServer(). The keys should be regularly\nregenerated and server's keys can be reset with\nserver.setTicketKeys().
Session ticket keys are cryptographic keys, and they must be stored\nsecurely. With TLS 1.2 and below, if they are compromised all sessions that\nused tickets encrypted with them can be decrypted. They should not be stored\non disk, and they should be regenerated regularly.
\nIf clients advertise support for tickets, the server will send them. The\nserver can disable tickets by supplying\nrequire('constants').SSL_OP_NO_TICKET in secureOptions.
Both session identifiers and session tickets timeout, causing the server to\ncreate new sessions. The timeout can be configured with the sessionTimeout\noption of tls.createServer().
For all the mechanisms, when resumption fails, servers will create new sessions.\nSince failing to resume the session does not cause TLS/HTTPS connection\nfailures, it is easy to not notice unnecessarily poor TLS performance. The\nOpenSSL CLI can be used to verify that servers are resuming sessions. Use the\n-reconnect option to openssl s_client, for example:
$ openssl s_client -connect localhost:443 -reconnect\nRead through the debug output. The first connection should say \"New\", for\nexample:
\nNew, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256\nSubsequent connections should say \"Reused\", for example:
\nReused, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256\nNode.js is built with a default suite of enabled and disabled TLS ciphers.\nCurrently, the default cipher suite is:
\nECDHE-RSA-AES128-GCM-SHA256:\nECDHE-ECDSA-AES128-GCM-SHA256:\nECDHE-RSA-AES256-GCM-SHA384:\nECDHE-ECDSA-AES256-GCM-SHA384:\nDHE-RSA-AES128-GCM-SHA256:\nECDHE-RSA-AES128-SHA256:\nDHE-RSA-AES128-SHA256:\nECDHE-RSA-AES256-SHA384:\nDHE-RSA-AES256-SHA384:\nECDHE-RSA-AES256-SHA256:\nDHE-RSA-AES256-SHA256:\nHIGH:\n!aNULL:\n!eNULL:\n!EXPORT:\n!DES:\n!RC4:\n!MD5:\n!PSK:\n!SRP:\n!CAMELLIA\nThis default can be replaced entirely using the --tls-cipher-list command\nline switch (directly, or via the NODE_OPTIONS environment variable). For\ninstance, the following makes ECDHE-RSA-AES128-GCM-SHA256:!RC4 the default TLS\ncipher suite:
node --tls-cipher-list=\"ECDHE-RSA-AES128-GCM-SHA256:!RC4\" server.js\n\nexport NODE_OPTIONS=--tls-cipher-list=\"ECDHE-RSA-AES128-GCM-SHA256:!RC4\"\nnode server.js\nThe default can also be replaced on a per client or server basis using the\nciphers option from tls.createSecureContext(), which is also available\nin tls.createServer(), tls.connect(), and when creating new\ntls.TLSSockets.
Consult OpenSSL cipher list format documentation for details on the format.
\nThe default cipher suite included within Node.js has been carefully\nselected to reflect current security best practices and risk mitigation.\nChanging the default cipher suite can have a significant impact on the security\nof an application. The --tls-cipher-list switch and ciphers option should by\nused only if absolutely necessary.
The default cipher suite prefers GCM ciphers for Chrome's 'modern\ncryptography' setting and also prefers ECDHE and DHE ciphers for Perfect\nForward Secrecy, while offering some backward compatibility.
\n128 bit AES is preferred over 192 and 256 bit AES in light of specific\nattacks affecting larger AES key sizes.
\nOld clients that rely on insecure and deprecated RC4 or DES-based ciphers\n(like Internet Explorer 6) cannot complete the handshaking process with\nthe default configuration. If these clients must be supported, the\nTLS recommendations may offer a compatible cipher suite. For more details\non the format, see the OpenSSL cipher list format documentation.
", "type": "module", "displayName": "Modifying the Default TLS Cipher suite" }, { "textRaw": "Deprecated APIs", "name": "deprecated_apis", "classes": [ { "textRaw": "Class: CryptoStream", "type": "class", "name": "CryptoStream", "meta": { "added": [ "v0.3.4" ], "deprecated": [ "v0.11.3" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`tls.TLSSocket`][] instead.", "desc": "The tls.CryptoStream class represents a stream of encrypted data. This class\nis deprecated and should no longer be used.
The cryptoStream.bytesWritten property returns the total number of bytes\nwritten to the underlying socket including the bytes required for the\nimplementation of the TLS protocol.
Returned by tls.createSecurePair().
The 'secure' event is emitted by the SecurePair object once a secure\nconnection has been established.
As with checking for the server\n'secureConnection'\nevent, pair.cleartext.authorized should be inspected to confirm whether the\ncertificate used is properly authorized.
Creates a new secure pair object with two streams, one of which reads and writes\nthe encrypted data and the other of which reads and writes the cleartext data.\nGenerally, the encrypted stream is piped to/from an incoming encrypted data\nstream and the cleartext one is used as a replacement for the initial encrypted\nstream.
\ntls.createSecurePair() returns a tls.SecurePair object with cleartext and\nencrypted stream properties.
Using cleartext has the same API as tls.TLSSocket.
The tls.createSecurePair() method is now deprecated in favor of\ntls.TLSSocket(). For example, the code:
pair = tls.createSecurePair(/* ... */);\npair.encrypted.pipe(socket);\nsocket.pipe(pair.encrypted);\ncan be replaced by:
\nsecureSocket = tls.TLSSocket(socket, options);\nwhere secureSocket has the same API as pair.cleartext.
The tls.Server class is a subclass of net.Server that accepts encrypted\nconnections using TLS or SSL.
The 'newSession' event is emitted upon creation of a new TLS session. This may\nbe used to store sessions in external storage. The data should be provided to\nthe 'resumeSession' callback.
The listener callback is passed three arguments when called:
\nsessionId <Buffer> The TLS session identifiersessionData <Buffer> The TLS session datacallback <Function> A callback function taking no arguments that must be\ninvoked in order for data to be sent or received over the secure connection.Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
" }, { "textRaw": "Event: 'OCSPRequest'", "type": "event", "name": "OCSPRequest", "meta": { "added": [ "v0.11.13" ], "changes": [] }, "params": [], "desc": "The 'OCSPRequest' event is emitted when the client sends a certificate status\nrequest. The listener callback is passed three arguments when called:
certificate <Buffer> The server certificateissuer <Buffer> The issuer's certificatecallback <Function> A callback function that must be invoked to provide\nthe results of the OCSP request.The server's current certificate can be parsed to obtain the OCSP URL\nand certificate ID; after obtaining an OCSP response, callback(null, resp) is\nthen invoked, where resp is a Buffer instance containing the OCSP response.\nBoth certificate and issuer are Buffer DER-representations of the\nprimary and issuer's certificates. These can be used to obtain the OCSP\ncertificate ID and OCSP endpoint URL.
Alternatively, callback(null, null) may be called, indicating that there was\nno OCSP response.
Calling callback(err) will result in a socket.destroy(err) call.
The typical flow of an OCSP Request is as follows:
\n'OCSPRequest' (via the status\ninfo extension in ClientHello).'OCSPRequest' event, calling the\nlistener if registered.certificate or issuer and\nperforms an OCSP request to the CA.'OCSPResponse' from the CA and sends it back to the client\nvia the callback argumentThe issuer can be null if the certificate is either self-signed or the\nissuer is not in the root certificates list. (An issuer may be provided\nvia the ca option when establishing the TLS connection.)
Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
\nAn npm module like asn1.js may be used to parse the certificates.
" }, { "textRaw": "Event: 'resumeSession'", "type": "event", "name": "resumeSession", "meta": { "added": [ "v0.9.2" ], "changes": [] }, "params": [], "desc": "The 'resumeSession' event is emitted when the client requests to resume a\nprevious TLS session. The listener callback is passed two arguments when\ncalled:
sessionId <Buffer> The TLS session identifiercallback <Function> A callback function to be called when the prior session\nhas been recovered: callback([err[, sessionData]])
The event listener should perform a lookup in external storage for the\nsessionData saved by the 'newSession' event handler using the given\nsessionId. If found, call callback(null, sessionData) to resume the session.\nIf not found, the session cannot be resumed. callback() must be called\nwithout sessionData so that the handshake can continue and a new session can\nbe created. It is possible to call callback(err) to terminate the incoming\nconnection and destroy the socket.
Listening for this event will have an effect only on connections established\nafter the addition of the event listener.
\nThe following illustrates resuming a TLS session:
\nconst tlsSessionStore = {};\nserver.on('newSession', (id, data, cb) => {\n tlsSessionStore[id.toString('hex')] = data;\n cb();\n});\nserver.on('resumeSession', (id, cb) => {\n cb(null, tlsSessionStore[id.toString('hex')] || null);\n});\nThe 'secureConnection' event is emitted after the handshaking process for a\nnew connection has successfully completed. The listener callback is passed a\nsingle argument when called:
tlsSocket <tls.TLSSocket> The established TLS socket.The tlsSocket.authorized property is a boolean indicating whether the\nclient has been verified by one of the supplied Certificate Authorities for the\nserver. If tlsSocket.authorized is false, then socket.authorizationError\nis set to describe how authorization failed. Note that depending on the settings\nof the TLS server, unauthorized connections may still be accepted.
The tlsSocket.alpnProtocol property is a string that contains the selected\nALPN protocol. When ALPN has no selected protocol, tlsSocket.alpnProtocol\nequals false.
The tlsSocket.servername property is a string containing the server name\nrequested via SNI.
The 'tlsClientError' event is emitted when an error occurs before a secure\nconnection is established. The listener callback is passed two arguments when\ncalled:
exception <Error> The Error object describing the errortlsSocket <tls.TLSSocket> The tls.TLSSocket instance from which the\nerror originated.The server.addContext() method adds a secure context that will be used if\nthe client request's SNI name matches the supplied hostname (or wildcard).
Returns the bound address, the address family name, and port of the\nserver as reported by the operating system. See net.Server.address() for\nmore information.
The server.close() method stops the server from accepting new connections.
This function operates asynchronously. The 'close' event will be emitted\nwhen the server has no more open connections.
Returns the session ticket keys.
\nSee Session Resumption for more information.
" }, { "textRaw": "server.listen()", "type": "method", "name": "listen", "signatures": [ { "params": [] } ], "desc": "Starts the server listening for encrypted connections.\nThis method is identical to server.listen() from net.Server.
Sets the session ticket keys.
\nChanges to the ticket keys are effective only for future server connections.\nExisting or currently pending server connections will use the previous keys.
\nSee Session Resumption for more information.
" } ], "properties": [ { "textRaw": "`connections` {number}", "type": "number", "name": "connections", "meta": { "added": [ "v0.3.2" ], "deprecated": [ "v0.9.7" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`server.getConnections()`][] instead.", "desc": "Returns the current number of concurrent connections on the server.
" } ] }, { "textRaw": "Class: tls.TLSSocket", "type": "class", "name": "tls.TLSSocket", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "The tls.TLSSocket is a subclass of net.Socket that performs transparent\nencryption of written data and all required TLS negotiation.
Instances of tls.TLSSocket implement the duplex Stream interface.
Methods that return TLS connection metadata (e.g.\ntls.TLSSocket.getPeerCertificate() will only return data while the\nconnection is open.
The 'OCSPResponse' event is emitted if the requestOCSP option was set\nwhen the tls.TLSSocket was created and an OCSP response has been received.\nThe listener callback is passed a single argument when called:
response <Buffer> The server's OCSP responseTypically, the response is a digitally signed object from the server's CA that\ncontains information about server's certificate revocation status.
The 'secureConnect' event is emitted after the handshaking process for a new\nconnection has successfully completed. The listener callback will be called\nregardless of whether or not the server's certificate has been authorized. It\nis the client's responsibility to check the tlsSocket.authorized property to\ndetermine if the server certificate was signed by one of the specified CAs. If\ntlsSocket.authorized === false, then the error can be found by examining the\ntlsSocket.authorizationError property. If ALPN was used, the\ntlsSocket.alpnProtocol property can be checked to determine the negotiated\nprotocol.
Returns the bound address, the address family name, and port of the\nunderlying socket as reported by the operating system:\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }.
Disables TLS renegotiation for this TLSSocket instance. Once called, attempts\nto renegotiate will trigger an 'error' event on the TLSSocket.
Returns an object representing the cipher name. The version key is a legacy\nfield which always contains the value 'TLSv1/SSLv3'.
For example: { name: 'AES256-SHA', version: 'TLSv1/SSLv3' }.
See SSL_CIPHER_get_name() in\nhttps://www.openssl.org/docs/man1.1.0/ssl/SSL_CIPHER_get_name.html for more\ninformation.
Returns an object representing the type, name, and size of parameter of\nan ephemeral key exchange in Perfect Forward Secrecy on a client\nconnection. It returns an empty object when the key exchange is not\nephemeral. As this is only supported on a client socket; null is returned\nif called on a server socket. The supported types are 'DH' and 'ECDH'. The\nname property is available only when type is 'ECDH'.
For example: { type: 'ECDH', name: 'prime256v1', size: 256 }.
As the Finished messages are message digests of the complete handshake\n(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can\nbe used for external authentication procedures when the authentication\nprovided by SSL/TLS is not desired or is not enough.
Corresponds to the SSL_get_finished routine in OpenSSL and may be used\nto implement the tls-unique channel binding from RFC 5929.
Returns an object representing the peer's certificate. The returned object has\nsome properties corresponding to the fields of the certificate.
\nIf the full certificate chain was requested, each certificate will include an\nissuerCertificate property containing an object representing its issuer's\ncertificate.
{ subject:\n { C: 'UK',\n ST: 'Acknack Ltd',\n L: 'Rhys Jones',\n O: 'node.js',\n OU: 'Test TLS Certificate',\n CN: 'localhost' },\n issuer:\n { C: 'UK',\n ST: 'Acknack Ltd',\n L: 'Rhys Jones',\n O: 'node.js',\n OU: 'Test TLS Certificate',\n CN: 'localhost' },\n issuerCertificate:\n { ... another certificate, possibly with an .issuerCertificate ... },\n raw: < RAW DER buffer >,\n pubkey: < RAW DER buffer >,\n valid_from: 'Nov 11 09:52:22 2009 GMT',\n valid_to: 'Nov 6 09:52:22 2029 GMT',\n fingerprint: '2A:7A:C2:DD:E5:F9:CC:53:72:35:99:7A:02:5A:71:38:52:EC:8A:DF',\n fingerprint256: '2A:7A:C2:DD:E5:F9:CC:53:72:35:99:7A:02:5A:71:38:52:EC:8A:DF:00:11:22:33:44:55:66:77:88:99:AA:BB',\n serialNumber: 'B9B0D332A1AA5635' }\nIf the peer does not provide a certificate, an empty object will be returned.
" }, { "textRaw": "tlsSocket.getPeerFinished()", "type": "method", "name": "getPeerFinished", "meta": { "added": [ "v9.9.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer|undefined} The latest `Finished` message that is expected or has actually been received from the socket as part of a SSL/TLS handshake, or `undefined` if there is no `Finished` message so far.", "name": "return", "type": "Buffer|undefined", "desc": "The latest `Finished` message that is expected or has actually been received from the socket as part of a SSL/TLS handshake, or `undefined` if there is no `Finished` message so far." }, "params": [] } ], "desc": "As the Finished messages are message digests of the complete handshake\n(with a total of 192 bits for TLS 1.0 and more for SSL 3.0), they can\nbe used for external authentication procedures when the authentication\nprovided by SSL/TLS is not desired or is not enough.
Corresponds to the SSL_get_peer_finished routine in OpenSSL and may be used\nto implement the tls-unique channel binding from RFC 5929.
Returns a string containing the negotiated SSL/TLS protocol version of the\ncurrent connection. The value 'unknown' will be returned for connected\nsockets that have not completed the handshaking process. The value null will\nbe returned for server sockets or disconnected client sockets.
Protocol versions are:
\n'TLSv1''TLSv1.1''TLSv1.2''SSLv3'See https://www.openssl.org/docs/man1.1.0/ssl/SSL_get_version.html for more\ninformation.
" }, { "textRaw": "tlsSocket.getSession()", "type": "method", "name": "getSession", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "{Buffer}", "type": "Buffer" } ] } ], "desc": "Returns the TLS session data or undefined if no session was\nnegotiated. On the client, the data can be provided to the session option of\ntls.connect() to resume the connection. On the server, it may be useful\nfor debugging.
See Session Resumption for more information.
" }, { "textRaw": "tlsSocket.getTLSTicket()", "type": "method", "name": "getTLSTicket", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "{Buffer}", "type": "Buffer" } ] } ], "desc": "For a client, returns the TLS session ticket if one is available, or\nundefined. For a server, always returns undefined.
It may be useful for debugging.
\nSee Session Resumption for more information.
" }, { "textRaw": "tlsSocket.isSessionReused()", "type": "method", "name": "isSessionReused", "meta": { "added": [ "v0.5.6" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean} `true` if the session was reused, `false` otherwise.", "name": "return", "type": "boolean", "desc": "`true` if the session was reused, `false` otherwise." }, "params": [] } ], "desc": "See Session Resumption for more information.
" }, { "textRaw": "tlsSocket.renegotiate(options, callback)", "type": "method", "name": "renegotiate", "meta": { "added": [ "v0.11.8" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`rejectUnauthorized` {boolean} If not `false`, the server certificate is verified against the list of supplied CAs. An `'error'` event is emitted if verification fails; `err.code` contains the OpenSSL error code. **Default:** `true`.", "name": "rejectUnauthorized", "type": "boolean", "default": "`true`", "desc": "If not `false`, the server certificate is verified against the list of supplied CAs. An `'error'` event is emitted if verification fails; `err.code` contains the OpenSSL error code." }, { "textRaw": "`requestCert`", "name": "requestCert" } ] }, { "textRaw": "`callback` {Function} A function that will be called when the renegotiation request has been completed.", "name": "callback", "type": "Function", "desc": "A function that will be called when the renegotiation request has been completed." } ] } ], "desc": "The tlsSocket.renegotiate() method initiates a TLS renegotiation process.\nUpon completion, the callback function will be passed a single argument\nthat is either an Error (if the request failed) or null.
This method can be used to request a peer's certificate after the secure\nconnection has been established.
\nWhen running as the server, the socket will be destroyed with an error after\nhandshakeTimeout timeout.
The tlsSocket.setMaxSendFragment() method sets the maximum TLS fragment size.\nReturns true if setting the limit succeeded; false otherwise.
Smaller fragment sizes decrease the buffering latency on the client: larger\nfragments are buffered by the TLS layer until the entire fragment is received\nand its integrity is verified; large fragments can span multiple roundtrips\nand their processing can be delayed due to packet loss or reordering. However,\nsmaller fragments add extra TLS framing bytes and CPU overhead, which may\ndecrease overall server throughput.
" } ], "properties": [ { "textRaw": "tlsSocket.authorizationError", "name": "authorizationError", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the reason why the peer's certificate was not been verified. This\nproperty is set only when tlsSocket.authorized === false.
Returns true if the peer certificate was signed by one of the CAs specified\nwhen creating the tls.TLSSocket instance, otherwise false.
Always returns true. This may be used to distinguish TLS sockets from regular\nnet.Socket instances.
Returns the string representation of the local IP address.
" }, { "textRaw": "`localPort` {number}", "type": "number", "name": "localPort", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the numeric representation of the local port.
" }, { "textRaw": "`remoteAddress` {string}", "type": "string", "name": "remoteAddress", "meta": { "added": [ "v0.11.4" ], "changes": [] }, "desc": "Returns the string representation of the remote IP address. For example,\n'74.125.127.100' or '2001:4860:a005::68'.
Returns the string representation of the remote IP family. 'IPv4' or 'IPv6'.
Returns the numeric representation of the remote port. For example, 443.
Construct a new tls.TLSSocket object from an existing TCP socket.
Verifies the certificate cert is issued to hostname.
Returns <Error> object, populating it with reason, host, and cert on\nfailure. On success, returns <undefined>.
This function can be overwritten by providing alternative function as part of\nthe options.checkServerIdentity option passed to tls.connect(). The\noverwriting function can call tls.checkServerIdentity() of course, to augment\nthe checks done with additional verification.
This function is only called if the certificate passed all other checks, such as\nbeing issued by trusted CA (options.ca).
The cert object contains the parsed certificate and will have a structure\nsimilar to:
\n{ subject:\n { OU: [ 'Domain Control Validated', 'PositiveSSL Wildcard' ],\n CN: '*.nodejs.org' },\n issuer:\n { C: 'GB',\n ST: 'Greater Manchester',\n L: 'Salford',\n O: 'COMODO CA Limited',\n CN: 'COMODO RSA Domain Validation Secure Server CA' },\n subjectaltname: 'DNS:*.nodejs.org, DNS:nodejs.org',\n infoAccess:\n { 'CA Issuers - URI':\n [ 'http://crt.comodoca.com/COMODORSADomainValidationSecureServerCA.crt' ],\n 'OCSP - URI': [ 'http://ocsp.comodoca.com' ] },\n modulus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n exponent: '0x10001',\n pubkey: <Buffer ... >,\n valid_from: 'Aug 14 00:00:00 2017 GMT',\n valid_to: 'Nov 20 23:59:59 2019 GMT',\n fingerprint: '01:02:59:D9:C3:D2:0D:08:F7:82:4E:44:A4:B4:53:C5:E2:3A:87:4D',\n fingerprint256: '69:AE:1A:6A:D4:3D:C6:C1:1B:EA:C6:23:DE:BA:2A:14:62:62:93:5C:7A:EA:06:41:9B:0B:BC:87:CE:48:4E:02',\n ext_key_usage: [ '1.3.6.1.5.5.7.3.1', '1.3.6.1.5.5.7.3.2' ],\n serialNumber: '66593D57F20CBC573E433381B5FEC280',\n raw: <Buffer ... > }\nThe callback function, if specified, will be added as a listener for the\n'secureConnect' event.
tls.connect() returns a tls.TLSSocket object.
The following illustrates a client for the echo server example from\ntls.createServer():
// Assumes an echo server that is listening on port 8000.\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n // Necessary only if the server requires client certificate authentication.\n key: fs.readFileSync('client-key.pem'),\n cert: fs.readFileSync('client-cert.pem'),\n\n // Necessary only if the server uses a self-signed certificate.\n ca: [ fs.readFileSync('server-cert.pem') ],\n\n // Necessary only if the server's cert isn't for \"localhost\".\n checkServerIdentity: () => { return null; },\n};\n\nconst socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n console.log('server ends connection');\n});\nSame as tls.connect() except that path can be provided\nas an argument instead of an option.
A path option, if specified, will take precedence over the path argument.
" }, { "textRaw": "tls.connect(port[, host][, options][, callback])", "type": "method", "name": "connect", "meta": { "added": [ "v0.11.3" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {tls.TLSSocket}", "name": "return", "type": "tls.TLSSocket" }, "params": [ { "textRaw": "`port` {number} Default value for `options.port`.", "name": "port", "type": "number", "desc": "Default value for `options.port`." }, { "textRaw": "`host` {string} Default value for `options.host`.", "name": "host", "type": "string", "desc": "Default value for `options.host`.", "optional": true }, { "textRaw": "`options` {Object} See [`tls.connect()`][].", "name": "options", "type": "Object", "desc": "See [`tls.connect()`][].", "optional": true }, { "textRaw": "`callback` {Function} See [`tls.connect()`][].", "name": "callback", "type": "Function", "desc": "See [`tls.connect()`][].", "optional": true } ] } ], "desc": "Same as tls.connect() except that port and host can be provided\nas arguments instead of options.
A port or host option, if specified, will take precedence over any port or host\nargument.
" }, { "textRaw": "tls.createSecureContext([options])", "type": "method", "name": "createSecureContext", "meta": { "added": [ "v0.11.13" ], "changes": [ { "version": "v10.16.0", "pr-url": "https://github.com/nodejs/node/pull/24405", "description": "The `minVersion` and `maxVersion` can be used to restrict the allowed TLS protocol versions." }, { "version": "v10.0.0", "pr-url": "https://github.com/nodejs/node/pull/19794", "description": "The `ecdhCurve` cannot be set to `false` anymore due to a change in OpenSSL." }, { "version": "v9.3.0", "pr-url": "https://github.com/nodejs/node/pull/14903", "description": "The `options` parameter can now include `clientCertEngine`." }, { "version": "v9.0.0", "pr-url": "https://github.com/nodejs/node/pull/15206", "description": "The `ecdhCurve` option can now be multiple `':'` separated curve names or `'auto'`." }, { "version": "v7.3.0", "pr-url": "https://github.com/nodejs/node/pull/10294", "description": "If the `key` option is an array, individual entries do not need a `passphrase` property anymore. `Array` entries can also just be `string`s or `Buffer`s now." }, { "version": "v5.2.0", "pr-url": "https://github.com/nodejs/node/pull/4099", "description": "The `ca` option can now be a single string containing multiple CA certificates." } ] }, "signatures": [ { "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`ca` {string|string[]|Buffer|Buffer[]} Optionally override the trusted CA certificates. Default is to trust the well-known CAs curated by Mozilla. Mozilla's CAs are completely replaced when CAs are explicitly specified using this option. The value can be a string or `Buffer`, or an `Array` of strings and/or `Buffer`s. Any string or `Buffer` can contain multiple PEM CAs concatenated together. The peer's certificate must be chainable to a CA trusted by the server for the connection to be authenticated. When using certificates that are not chainable to a well-known CA, the certificate's CA must be explicitly specified as a trusted or the connection will fail to authenticate. If the peer uses a certificate that doesn't match or chain to one of the default CAs, use the `ca` option to provide a CA certificate that the peer's certificate can match or chain to. For self-signed certificates, the certificate is its own CA, and must be provided. For PEM encoded certificates, supported types are \"X509 CERTIFICATE\", and \"CERTIFICATE\".", "name": "ca", "type": "string|string[]|Buffer|Buffer[]", "desc": "Optionally override the trusted CA certificates. Default is to trust the well-known CAs curated by Mozilla. Mozilla's CAs are completely replaced when CAs are explicitly specified using this option. The value can be a string or `Buffer`, or an `Array` of strings and/or `Buffer`s. Any string or `Buffer` can contain multiple PEM CAs concatenated together. The peer's certificate must be chainable to a CA trusted by the server for the connection to be authenticated. When using certificates that are not chainable to a well-known CA, the certificate's CA must be explicitly specified as a trusted or the connection will fail to authenticate. If the peer uses a certificate that doesn't match or chain to one of the default CAs, use the `ca` option to provide a CA certificate that the peer's certificate can match or chain to. For self-signed certificates, the certificate is its own CA, and must be provided. For PEM encoded certificates, supported types are \"X509 CERTIFICATE\", and \"CERTIFICATE\"." }, { "textRaw": "`cert` {string|string[]|Buffer|Buffer[]} Cert chains in PEM format. One cert chain should be provided per private key. Each cert chain should consist of the PEM formatted certificate for a provided private `key`, followed by the PEM formatted intermediate certificates (if any), in order, and not including the root CA (the root CA must be pre-known to the peer, see `ca`). When providing multiple cert chains, they do not have to be in the same order as their private keys in `key`. If the intermediate certificates are not provided, the peer will not be able to validate the certificate, and the handshake will fail.", "name": "cert", "type": "string|string[]|Buffer|Buffer[]", "desc": "Cert chains in PEM format. One cert chain should be provided per private key. Each cert chain should consist of the PEM formatted certificate for a provided private `key`, followed by the PEM formatted intermediate certificates (if any), in order, and not including the root CA (the root CA must be pre-known to the peer, see `ca`). When providing multiple cert chains, they do not have to be in the same order as their private keys in `key`. If the intermediate certificates are not provided, the peer will not be able to validate the certificate, and the handshake will fail." }, { "textRaw": "`ciphers` {string} Cipher suite specification, replacing the default. For more information, see [modifying the default cipher suite][].", "name": "ciphers", "type": "string", "desc": "Cipher suite specification, replacing the default. For more information, see [modifying the default cipher suite][]." }, { "textRaw": "`clientCertEngine` {string} Name of an OpenSSL engine which can provide the client certificate.", "name": "clientCertEngine", "type": "string", "desc": "Name of an OpenSSL engine which can provide the client certificate." }, { "textRaw": "`crl` {string|string[]|Buffer|Buffer[]} PEM formatted CRLs (Certificate Revocation Lists).", "name": "crl", "type": "string|string[]|Buffer|Buffer[]", "desc": "PEM formatted CRLs (Certificate Revocation Lists)." }, { "textRaw": "`dhparam` {string|Buffer} Diffie Hellman parameters, required for [Perfect Forward Secrecy][]. Use `openssl dhparam` to create the parameters. The key length must be greater than or equal to 1024 bits, otherwise an error will be thrown. It is strongly recommended to use 2048 bits or larger for stronger security. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not be available.", "name": "dhparam", "type": "string|Buffer", "desc": "Diffie Hellman parameters, required for [Perfect Forward Secrecy][]. Use `openssl dhparam` to create the parameters. The key length must be greater than or equal to 1024 bits, otherwise an error will be thrown. It is strongly recommended to use 2048 bits or larger for stronger security. If omitted or invalid, the parameters are silently discarded and DHE ciphers will not be available." }, { "textRaw": "`ecdhCurve` {string} A string describing a named curve or a colon separated list of curve NIDs or names, for example `P-521:P-384:P-256`, to use for ECDH key agreement. Set to `auto` to select the curve automatically. Use [`crypto.getCurves()`][] to obtain a list of available curve names. On recent releases, `openssl ecparam -list_curves` will also display the name and description of each available elliptic curve. **Default:** [`tls.DEFAULT_ECDH_CURVE`].", "name": "ecdhCurve", "type": "string", "default": "[`tls.DEFAULT_ECDH_CURVE`]", "desc": "A string describing a named curve or a colon separated list of curve NIDs or names, for example `P-521:P-384:P-256`, to use for ECDH key agreement. Set to `auto` to select the curve automatically. Use [`crypto.getCurves()`][] to obtain a list of available curve names. On recent releases, `openssl ecparam -list_curves` will also display the name and description of each available elliptic curve." }, { "textRaw": "`honorCipherOrder` {boolean} Attempt to use the server's cipher suite preferences instead of the client's. When `true`, causes `SSL_OP_CIPHER_SERVER_PREFERENCE` to be set in `secureOptions`, see [OpenSSL Options][] for more information.", "name": "honorCipherOrder", "type": "boolean", "desc": "Attempt to use the server's cipher suite preferences instead of the client's. When `true`, causes `SSL_OP_CIPHER_SERVER_PREFERENCE` to be set in `secureOptions`, see [OpenSSL Options][] for more information." }, { "textRaw": "`key` {string|string[]|Buffer|Buffer[]|Object[]} Private keys in PEM format. PEM allows the option of private keys being encrypted. Encrypted keys will be decrypted with `options.passphrase`. Multiple keys using different algorithms can be provided either as an array of unencrypted key strings or buffers, or an array of objects in the form `{pem:tls.createServer() sets the default value of the honorCipherOrder option\nto true, other APIs that create secure contexts leave it unset.
tls.createServer() uses a 128 bit truncated SHA1 hash value generated\nfrom process.argv as the default value of the sessionIdContext option, other\nAPIs that create secure contexts have no default value.
The tls.createSecureContext() method creates a credentials object.
A key is required for ciphers that make use of certificates. Either key or\npfx can be used to provide it.
If the 'ca' option is not given, then Node.js will use the default\npublicly trusted list of CAs as given in\nhttps://hg.mozilla.org/mozilla-central/raw-file/tip/security/nss/lib/ckfw/builtins/certdata.txt.
" }, { "textRaw": "tls.createServer([options][, secureConnectionListener])", "type": "method", "name": "createServer", "meta": { "added": [ "v0.3.2" ], "changes": [ { "version": "v9.3.0", "pr-url": "https://github.com/nodejs/node/pull/14903", "description": "The `options` parameter can now include `clientCertEngine`." }, { "version": "v8.0.0", "pr-url": "https://github.com/nodejs/node/pull/11984", "description": "The `ALPNProtocols` option can be a `Uint8Array` now." }, { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2564", "description": "ALPN options are supported now." } ] }, "signatures": [ { "return": { "textRaw": "Returns: {tls.Server}", "name": "return", "type": "tls.Server" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`ALPNProtocols`: {string[]|Buffer[]|Uint8Array[]|Buffer|Uint8Array} An array of strings, `Buffer`s or `Uint8Array`s, or a single `Buffer` or `Uint8Array` containing the supported ALPN protocols. `Buffer`s should have the format `[len][name][len][name]...` e.g. `0x05hello0x05world`, where the first byte is the length of the next protocol name. Passing an array is usually much simpler, e.g. `['hello', 'world']`. (Protocols should be ordered by their priority.)", "name": "ALPNProtocols", "type": "string[]|Buffer[]|Uint8Array[]|Buffer|Uint8Array", "desc": "An array of strings, `Buffer`s or `Uint8Array`s, or a single `Buffer` or `Uint8Array` containing the supported ALPN protocols. `Buffer`s should have the format `[len][name][len][name]...` e.g. `0x05hello0x05world`, where the first byte is the length of the next protocol name. Passing an array is usually much simpler, e.g. `['hello', 'world']`. (Protocols should be ordered by their priority.)" }, { "textRaw": "`clientCertEngine` {string} Name of an OpenSSL engine which can provide the client certificate.", "name": "clientCertEngine", "type": "string", "desc": "Name of an OpenSSL engine which can provide the client certificate." }, { "textRaw": "`handshakeTimeout` {number} Abort the connection if the SSL/TLS handshake does not finish in the specified number of milliseconds. A `'tlsClientError'` is emitted on the `tls.Server` object whenever a handshake times out. **Default:** `120000` (120 seconds).", "name": "handshakeTimeout", "type": "number", "default": "`120000` (120 seconds)", "desc": "Abort the connection if the SSL/TLS handshake does not finish in the specified number of milliseconds. A `'tlsClientError'` is emitted on the `tls.Server` object whenever a handshake times out." }, { "textRaw": "`rejectUnauthorized` {boolean} If not `false` the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if `requestCert` is `true`. **Default:** `true`.", "name": "rejectUnauthorized", "type": "boolean", "default": "`true`", "desc": "If not `false` the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if `requestCert` is `true`." }, { "textRaw": "`requestCert` {boolean} If `true` the server will request a certificate from clients that connect and attempt to verify that certificate. **Default:** `false`.", "name": "requestCert", "type": "boolean", "default": "`false`", "desc": "If `true` the server will request a certificate from clients that connect and attempt to verify that certificate." }, { "textRaw": "`sessionTimeout` {number} The number of seconds after which a TLS session created by the server will no longer be resumable. See [Session Resumption][] for more information. **Default:** `300`.", "name": "sessionTimeout", "type": "number", "default": "`300`", "desc": "The number of seconds after which a TLS session created by the server will no longer be resumable. See [Session Resumption][] for more information." }, { "textRaw": "`SNICallback(servername, cb)` {Function} A function that will be called if the client supports SNI TLS extension. Two arguments will be passed when called: `servername` and `cb`. `SNICallback` should invoke `cb(null, ctx)`, where `ctx` is a `SecureContext` instance. (`tls.createSecureContext(...)` can be used to get a proper `SecureContext`.) If `SNICallback` wasn't provided the default callback with high-level API will be used (see below).", "name": "SNICallback(servername,", "desc": "cb)` {Function} A function that will be called if the client supports SNI TLS extension. Two arguments will be passed when called: `servername` and `cb`. `SNICallback` should invoke `cb(null, ctx)`, where `ctx` is a `SecureContext` instance. (`tls.createSecureContext(...)` can be used to get a proper `SecureContext`.) If `SNICallback` wasn't provided the default callback with high-level API will be used (see below)." }, { "textRaw": "`ticketKeys`: {Buffer} 48-bytes of cryptographically strong pseudo-random data. See [Session Resumption][] for more information.", "name": "ticketKeys", "type": "Buffer", "desc": "48-bytes of cryptographically strong pseudo-random data. See [Session Resumption][] for more information." }, { "textRaw": "...: Any [`tls.createSecureContext()`][] option can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required.", "name": "...", "desc": "Any [`tls.createSecureContext()`][] option can be provided. For servers, the identity options (`pfx` or `key`/`cert`) are usually required." } ], "optional": true }, { "textRaw": "`secureConnectionListener` {Function}", "name": "secureConnectionListener", "type": "Function", "optional": true } ] } ], "desc": "Creates a new tls.Server. The secureConnectionListener, if provided, is\nautomatically set as a listener for the 'secureConnection' event.
The ticketKeys options is automatically shared between cluster module\nworkers.
The following illustrates a simple echo server:
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n key: fs.readFileSync('server-key.pem'),\n cert: fs.readFileSync('server-cert.pem'),\n\n // This is necessary only if using client certificate authentication.\n requestCert: true,\n\n // This is necessary only if the client uses a self-signed certificate.\n ca: [ fs.readFileSync('client-cert.pem') ]\n};\n\nconst server = tls.createServer(options, (socket) => {\n console.log('server connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n socket.write('welcome!\\n');\n socket.setEncoding('utf8');\n socket.pipe(socket);\n});\nserver.listen(8000, () => {\n console.log('server bound');\n});\nThe server can be tested by connecting to it using the example client from\ntls.connect().
Returns an array with the names of the supported SSL ciphers.
\nconsole.log(tls.getCiphers()); // ['AES128-SHA', 'AES256-SHA', ...]\nThe default curve name to use for ECDH key agreement in a tls server. The\ndefault value is 'auto'. See tls.createSecureContext() for further\ninformation.
Trace Event provides a mechanism to centralize tracing information generated by\nV8, Node.js core, and userspace code.
\nTracing can be enabled with the --trace-event-categories command-line flag\nor by using the trace_events module. The --trace-event-categories flag\naccepts a list of comma-separated category names.
The available categories are:
\nnode - An empty placeholder.node.async_hooks - Enables capture of detailed async_hooks trace data.\nThe async_hooks events have a unique asyncId and a special triggerId\ntriggerAsyncId property.node.bootstrap - Enables capture of Node.js bootstrap milestones.node.fs.sync - Enables capture of trace data for file system sync methods.node.perf - Enables capture of Performance API measurements.
node.perf.usertiming - Enables capture of only Performance API User Timing\nmeasures and marks.node.perf.timerify - Enables capture of only Performance API timerify\nmeasurements.node.promises.rejections - Enables capture of trace data tracking the number\nof unhandled Promise rejections and handled-after-rejections.node.vm.script - Enables capture of trace data for the vm module's\nrunInNewContext(), runInContext(), and runInThisContext() methods.v8 - The V8 events are GC, compiling, and execution related.By default the node, node.async_hooks, and v8 categories are enabled.
node --trace-event-categories v8,node,node.async_hooks server.js\nPrior versions of Node.js required the use of the --trace-events-enabled\nflag to enable trace events. This requirement has been removed. However, the\n--trace-events-enabled flag may still be used and will enable the\nnode, node.async_hooks, and v8 trace event categories by default.
node --trace-events-enabled\n\n// is equivalent to\n\nnode --trace-event-categories v8,node,node.async_hooks\nAlternatively, trace events may be enabled using the trace_events module:
const trace_events = require('trace_events');\nconst tracing = trace_events.createTracing({ categories: ['node.perf'] });\ntracing.enable(); // Enable trace event capture for the 'node.perf' category\n\n// do work\n\ntracing.disable(); // Disable trace event capture for the 'node.perf' category\nRunning Node.js with tracing enabled will produce log files that can be opened\nin the chrome://tracing\ntab of Chrome.
The logging file is by default called node_trace.${rotation}.log, where\n${rotation} is an incrementing log-rotation id. The filepath pattern can\nbe specified with --trace-event-file-pattern that accepts a template\nstring that supports ${rotation} and ${pid}:
node --trace-event-categories v8 --trace-event-file-pattern '${pid}-${rotation}.log' server.js\nStarting with Node.js 10.0.0, the tracing system uses the same time source\nas the one used by process.hrtime()\nhowever the trace-event timestamps are expressed in microseconds,\nunlike process.hrtime() which returns nanoseconds.
The Tracing object is used to enable or disable tracing for sets of\ncategories. Instances are created using the trace_events.createTracing()\nmethod.
When created, the Tracing object is disabled. Calling the\ntracing.enable() method adds the categories to the set of enabled trace event\ncategories. Calling tracing.disable() will remove the categories from the\nset of enabled trace event categories.
A comma-separated list of the trace event categories covered by this\nTracing object.
Disables this Tracing object.
Only trace event categories not covered by other enabled Tracing objects\nand not specified by the --trace-event-categories flag will be disabled.
const trace_events = require('trace_events');\nconst t1 = trace_events.createTracing({ categories: ['node', 'v8'] });\nconst t2 = trace_events.createTracing({ categories: ['node.perf', 'node'] });\nt1.enable();\nt2.enable();\n\n// Prints 'node,node.perf,v8'\nconsole.log(trace_events.getEnabledCategories());\n\nt2.disable(); // will only disable emission of the 'node.perf' category\n\n// Prints 'node,v8'\nconsole.log(trace_events.getEnabledCategories());\nEnables this Tracing object for the set of categories covered by the\nTracing object.
true only if the Tracing object has been enabled.options <Object>
categories <string[]> An array of trace category names. Values included\nin the array are coerced to a string when possible. An error will be\nthrown if the value cannot be coerced.Creates and returns a Tracing object for the given set of categories.
const trace_events = require('trace_events');\nconst categories = ['node.perf', 'node.async_hooks'];\nconst tracing = trace_events.createTracing({ categories });\ntracing.enable();\n// do stuff\ntracing.disable();\nReturns a comma-separated list of all currently-enabled trace event\ncategories. The current set of enabled trace event categories is determined\nby the union of all currently-enabled Tracing objects and any categories\nenabled using the --trace-event-categories flag.
Given the file test.js below, the command\nnode --trace-event-categories node.perf test.js will print\n'node.async_hooks,node.perf' to the console.
const trace_events = require('trace_events');\nconst t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });\nconst t2 = trace_events.createTracing({ categories: ['node.perf'] });\nconst t3 = trace_events.createTracing({ categories: ['v8'] });\n\nt1.enable();\nt2.enable();\n\nconsole.log(trace_events.getEnabledCategories());\nThe tty module provides the tty.ReadStream and tty.WriteStream classes.\nIn most cases, it will not be necessary or possible to use this module directly.\nHowever, it can be accessed using:
const tty = require('tty');\nWhen Node.js detects that it is being run with a text terminal (\"TTY\")\nattached, process.stdin will, by default, be initialized as an instance of\ntty.ReadStream and both process.stdout and process.stderr will, by\ndefault be instances of tty.WriteStream. The preferred method of determining\nwhether Node.js is being run within a TTY context is to check that the value of\nthe process.stdout.isTTY property is true:
$ node -p -e \"Boolean(process.stdout.isTTY)\"\ntrue\n$ node -p -e \"Boolean(process.stdout.isTTY)\" | cat\nfalse\nIn most cases, there should be little to no reason for an application to\nmanually create instances of the tty.ReadStream and tty.WriteStream\nclasses.
The tty.ReadStream class is a subclass of net.Socket that represents the\nreadable side of a TTY. In normal circumstances process.stdin will be the\nonly tty.ReadStream instance in a Node.js process and there should be no\nreason to create additional instances.
A boolean that is true if the TTY is currently configured to operate as a\nraw device. Defaults to false.
A boolean that is always true for tty.ReadStream instances.
Allows configuration of tty.ReadStream so that it operates as a raw device.
When in raw mode, input is always available character-by-character, not\nincluding modifiers. Additionally, all special processing of characters by the\nterminal is disabled, including echoing input characters.\nNote that CTRL+C will no longer cause a SIGINT when in this mode.
The tty.WriteStream class is a subclass of net.Socket that represents\nthe writable side of a TTY. In normal circumstances, process.stdout and\nprocess.stderr will be the only tty.WriteStream instances created for a\nNode.js process and there should be no reason to create additional instances.
The 'resize' event is emitted whenever either of the writeStream.columns\nor writeStream.rows properties have changed. No arguments are passed to the\nlistener callback when called.
process.stdout.on('resize', () => {\n console.log('screen size has changed!');\n console.log(`${process.stdout.columns}x${process.stdout.rows}`);\n});\nwriteStream.clearLine() clears the current line of this WriteStream in a\ndirection identified by dir.
writeStream.clearScreenDown() clears this WriteStream from the current\ncursor down.
writeStream.cursorTo() moves this WriteStream's cursor to the specified\nposition.
Returns:
\n1 for 2,4 for 16,8 for 256,24 for 16,777,216\ncolors supported.Use this to determine what colors the terminal supports. Due to the nature of\ncolors in terminals it is possible to either have false positives or false\nnegatives. It depends on process information and the environment variables that\nmay lie about what terminal is used.\nTo enforce a specific behavior without relying on process.env it is possible\nto pass in an object with different settings.
Use the NODE_DISABLE_COLORS environment variable to enforce this function to\nalways return 1.
writeStream.getWindowSize() returns the size of the TTY\ncorresponding to this WriteStream. The array is of the type\n[numColumns, numRows] where numColumns and numRows represent the number\nof columns and rows in the corresponding TTY.
Returns true if the writeStream supports at least as many colors as provided\nin count. Minimum support is 2 (black and white).
This has the same false positives and negatives as described in\nwriteStream.getColorDepth().
process.stdout.hasColors();\n// Returns true or false depending on if `stdout` supports at least 16 colors.\nprocess.stdout.hasColors(256);\n// Returns true or false depending on if `stdout` supports at least 256 colors.\nprocess.stdout.hasColors({ TMUX: '1' });\n// Returns true.\nprocess.stdout.hasColors(2 ** 24, { TMUX: '1' });\n// Returns false (the environment setting pretends to support 2 ** 8 colors).\nwriteStream.moveCursor() moves this WriteStream's cursor relative to its\ncurrent position.
A number specifying the number of columns the TTY currently has. This property\nis updated whenever the 'resize' event is emitted.
A boolean that is always true.
A number specifying the number of rows the TTY currently has. This property\nis updated whenever the 'resize' event is emitted.
The tty.isatty() method returns true if the given fd is associated with\na TTY and false if it is not, including whenever fd is not a non-negative\ninteger.
The dgram module provides an implementation of UDP Datagram sockets.
const dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// server listening 0.0.0.0:41234\nThe dgram.Socket object is an EventEmitter that encapsulates the\ndatagram functionality.
New instances of dgram.Socket are created using dgram.createSocket().\nThe new keyword is not to be used to create dgram.Socket instances.
The 'close' event is emitted after a socket is closed with close().\nOnce triggered, no new 'message' events will be emitted on this socket.
The 'error' event is emitted whenever any error occurs. The event handler\nfunction is passed a single Error object.
The 'listening' event is emitted whenever a socket begins listening for\ndatagram messages. This occurs as soon as UDP sockets are created.
The 'message' event is emitted when a new datagram is available on a socket.\nThe event handler function is passed two arguments: msg and rinfo.
Tells the kernel to join a multicast group at the given multicastAddress and\nmulticastInterface using the IP_ADD_MEMBERSHIP socket option. If the\nmulticastInterface argument is not specified, the operating system will choose\none interface and will add membership to it. To add membership to every\navailable interface, call addMembership multiple times, once per interface.
When sharing a UDP socket across multiple cluster workers, the\nsocket.addMembership() function must be called only once or an\nEADDRINUSE error will occur:
const cluster = require('cluster');\nconst dgram = require('dgram');\nif (cluster.isMaster) {\n cluster.fork(); // Works ok.\n cluster.fork(); // Fails with EADDRINUSE.\n} else {\n const s = dgram.createSocket('udp4');\n s.bind(1234, () => {\n s.addMembership('224.0.0.114');\n });\n}\nReturns an object containing the address information for a socket.\nFor UDP sockets, this object will contain address, family and port\nproperties.
For UDP sockets, causes the dgram.Socket to listen for datagram\nmessages on a named port and optional address. If port is not\nspecified or is 0, the operating system will attempt to bind to a\nrandom port. If address is not specified, the operating system will\nattempt to listen on all addresses. Once binding is complete, a\n'listening' event is emitted and the optional callback function is\ncalled.
Note that specifying both a 'listening' event listener and passing a\ncallback to the socket.bind() method is not harmful but not very\nuseful.
A bound datagram socket keeps the Node.js process running to receive\ndatagram messages.
\nIf binding fails, an 'error' event is generated. In rare case (e.g.\nattempting to bind with a closed socket), an Error may be thrown.
Example of a UDP server listening on port 41234:
\nconst dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n const address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// server listening 0.0.0.0:41234\nFor UDP sockets, causes the dgram.Socket to listen for datagram\nmessages on a named port and optional address that are passed as\nproperties of an options object passed as the first argument. If\nport is not specified or is 0, the operating system will attempt\nto bind to a random port. If address is not specified, the operating\nsystem will attempt to listen on all addresses. Once binding is\ncomplete, a 'listening' event is emitted and the optional callback\nfunction is called.
Note that specifying both a 'listening' event listener and passing a\ncallback to the socket.bind() method is not harmful but not very\nuseful.
The options object may contain an additional exclusive property that is\nuse when using dgram.Socket objects with the cluster module. When\nexclusive is set to false (the default), cluster workers will use the same\nunderlying socket handle allowing connection handling duties to be shared.\nWhen exclusive is true, however, the handle is not shared and attempted\nport sharing results in an error.
A bound datagram socket keeps the Node.js process running to receive\ndatagram messages.
\nIf binding fails, an 'error' event is generated. In rare case (e.g.\nattempting to bind with a closed socket), an Error may be thrown.
An example socket listening on an exclusive port is shown below.
\nsocket.bind({\n address: 'localhost',\n port: 8000,\n exclusive: true\n});\nClose the underlying socket and stop listening for data on it. If a callback is\nprovided, it is added as a listener for the 'close' event.
Instructs the kernel to leave a multicast group at multicastAddress using the\nIP_DROP_MEMBERSHIP socket option. This method is automatically called by the\nkernel when the socket is closed or the process terminates, so most apps will\nnever have reason to call this.
If multicastInterface is not specified, the operating system will attempt to\ndrop membership on all valid interfaces.
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref() method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active. The socket.ref() method adds the socket back to the reference\ncounting and restores the default behavior.
Calling socket.ref() multiples times will have no additional effect.
The socket.ref() method returns a reference to the socket so calls can be\nchained.
Broadcasts a datagram on the socket. The destination port and address must\nbe specified.
The msg argument contains the message to be sent.\nDepending on its type, different behavior can apply. If msg is a Buffer\nor Uint8Array,\nthe offset and length specify the offset within the Buffer where the\nmessage begins and the number of bytes in the message, respectively.\nIf msg is a String, then it is automatically converted to a Buffer\nwith 'utf8' encoding. With messages that\ncontain multi-byte characters, offset and length will be calculated with\nrespect to byte length and not the character position.\nIf msg is an array, offset and length must not be specified.
The address argument is a string. If the value of address is a host name,\nDNS will be used to resolve the address of the host. If address is not\nprovided or otherwise falsy, '127.0.0.1' (for udp4 sockets) or '::1'\n(for udp6 sockets) will be used by default.
If the socket has not been previously bound with a call to bind, the socket\nis assigned a random port number and is bound to the \"all interfaces\" address\n('0.0.0.0' for udp4 sockets, '::0' for udp6 sockets.)
An optional callback function may be specified to as a way of reporting\nDNS errors or for determining when it is safe to reuse the buf object.\nNote that DNS lookups delay the time to send for at least one tick of the\nNode.js event loop.
The only way to know for sure that the datagram has been sent is by using a\ncallback. If an error occurs and a callback is given, the error will be\npassed as the first argument to the callback. If a callback is not given,\nthe error is emitted as an 'error' event on the socket object.
Offset and length are optional but both must be set if either are used.\nThey are supported only when the first argument is a Buffer or Uint8Array.
Example of sending a UDP packet to a port on localhost;
const dgram = require('dgram');\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.send(message, 41234, 'localhost', (err) => {\n client.close();\n});\nExample of sending a UDP packet composed of multiple buffers to a port on\n127.0.0.1;
const dgram = require('dgram');\nconst buf1 = Buffer.from('Some ');\nconst buf2 = Buffer.from('bytes');\nconst client = dgram.createSocket('udp4');\nclient.send([buf1, buf2], 41234, (err) => {\n client.close();\n});\nSending multiple buffers might be faster or slower depending on the\napplication and operating system. It is important to run benchmarks to\ndetermine the optimal strategy on a case-by-case basis. Generally speaking,\nhowever, sending multiple buffers is faster.
\nA Note about UDP datagram size
\nThe maximum size of an IPv4/v6 datagram depends on the MTU\n(Maximum Transmission Unit) and on the Payload Length field size.
The Payload Length field is 16 bits wide, which means that a normal\npayload exceed 64K octets including the internet header and data\n(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header);\nthis is generally true for loopback interfaces, but such long datagram\nmessages are impractical for most hosts and networks.
The MTU is the largest size a given link layer technology can support for\ndatagram messages. For any link, IPv4 mandates a minimum MTU of 68\noctets, while the recommended MTU for IPv4 is 576 (typically recommended\nas the MTU for dial-up type applications), whether they arrive whole or in\nfragments.
For IPv6, the minimum MTU is 1280 octets, however, the mandatory minimum\nfragment reassembly buffer size is 1500 octets. The value of 68 octets is\nvery small, since most current link layer technologies, like Ethernet, have a\nminimum MTU of 1500.
It is impossible to know in advance the MTU of each link through which\na packet might travel. Sending a datagram greater than the receiver MTU will\nnot work because the packet will get silently dropped without informing the\nsource that the data did not reach its intended recipient.
Sets or clears the SO_BROADCAST socket option. When set to true, UDP\npackets may be sent to a local interface's broadcast address.
All references to scope in this section are referring to\nIPv6 Zone Indices, which are defined by RFC 4007. In string form, an IP\nwith a scope index is written as 'IP%scope' where scope is an interface name\nor interface number.
Sets the default outgoing multicast interface of the socket to a chosen\ninterface or back to system interface selection. The multicastInterface must\nbe a valid string representation of an IP from the socket's family.
For IPv4 sockets, this should be the IP configured for the desired physical\ninterface. All packets sent to multicast on the socket will be sent on the\ninterface determined by the most recent successful use of this call.
\nFor IPv6 sockets, multicastInterface should include a scope to indicate the\ninterface as in the examples that follow. In IPv6, individual send calls can\nalso use explicit scope in addresses, so only packets sent to a multicast\naddress without specifying an explicit scope are affected by the most recent\nsuccessful use of this call.
On most systems, where scope format uses the interface name:
\nconst socket = dgram.createSocket('udp6');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('::%eth1');\n});\nOn Windows, where scope format uses an interface number:
\nconst socket = dgram.createSocket('udp6');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('::%2');\n});\nAll systems use an IP of the host on the desired physical interface:
\nconst socket = dgram.createSocket('udp4');\n\nsocket.bind(1234, () => {\n socket.setMulticastInterface('10.0.0.2');\n});\nA call on a socket that is not ready to send or no longer open may throw a Not\nrunning Error.
If multicastInterface can not be parsed into an IP then an EINVAL\nSystem Error is thrown.
On IPv4, if multicastInterface is a valid address but does not match any\ninterface, or if the address does not match the family then\na System Error such as EADDRNOTAVAIL or EPROTONOSUP is thrown.
On IPv6, most errors with specifying or omitting scope will result in the socket\ncontinuing to use (or returning to) the system's default interface selection.
\nA socket's address family's ANY address (IPv4 '0.0.0.0' or IPv6 '::') can be\nused to return control of the sockets default outgoing interface to the system\nfor future multicast packets.
Sets or clears the IP_MULTICAST_LOOP socket option. When set to true,\nmulticast packets will also be received on the local interface.
Sets the IP_MULTICAST_TTL socket option. While TTL generally stands for\n\"Time to Live\", in this context it specifies the number of IP hops that a\npacket is allowed to travel through, specifically for multicast traffic. Each\nrouter or gateway that forwards a packet decrements the TTL. If the TTL is\ndecremented to 0 by a router, it will not be forwarded.
The argument passed to socket.setMulticastTTL() is a number of hops\nbetween 0 and 255. The default on most systems is 1 but can vary.
Sets the SO_RCVBUF socket option. Sets the maximum socket receive buffer\nin bytes.
Sets the SO_SNDBUF socket option. Sets the maximum socket send buffer\nin bytes.
Sets the IP_TTL socket option. While TTL generally stands for \"Time to Live\",\nin this context it specifies the number of IP hops that a packet is allowed to\ntravel through. Each router or gateway that forwards a packet decrements the\nTTL. If the TTL is decremented to 0 by a router, it will not be forwarded.\nChanging TTL values is typically done for network probes or when multicasting.
The argument to socket.setTTL() is a number of hops between 1 and 255.\nThe default on most systems is 64 but can vary.
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref() method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active, allowing the process to exit even if the socket is still\nlistening.
Calling socket.unref() multiple times will have no addition effect.
The socket.unref() method returns a reference to the socket so calls can be\nchained.
As of Node.js v0.10, dgram.Socket#bind() changed to an asynchronous\nexecution model. Legacy code would use synchronous behavior:
const s = dgram.createSocket('udp4');\ns.bind(1234);\ns.addMembership('224.0.0.114');\nSuch legacy code would need to be changed to pass a callback function to the\ndgram.Socket#bind() function:
const s = dgram.createSocket('udp4');\ns.bind(1234, () => {\n s.addMembership('224.0.0.114');\n});\nCreates a dgram.Socket object. Once the socket is created, calling\nsocket.bind() will instruct the socket to begin listening for datagram\nmessages. When address and port are not passed to socket.bind() the\nmethod will bind the socket to the \"all interfaces\" address on a random port\n(it does the right thing for both udp4 and udp6 sockets). The bound address\nand port can be retrieved using socket.address().address and\nsocket.address().port.
Creates a dgram.Socket object of the specified type. The type argument\ncan be either 'udp4' or 'udp6'. An optional callback function can be\npassed which is added as a listener for 'message' events.
Once the socket is created, calling socket.bind() will instruct the\nsocket to begin listening for datagram messages. When address and port are\nnot passed to socket.bind() the method will bind the socket to the \"all\ninterfaces\" address on a random port (it does the right thing for both udp4\nand udp6 sockets). The bound address and port can be retrieved using\nsocket.address().address and socket.address().port.
The url module provides utilities for URL resolution and parsing. It can be\naccessed using:
const url = require('url');\nA URL string is a structured string containing multiple meaningful components.\nWhen parsed, a URL object is returned containing properties for each of these\ncomponents.
\nThe url module provides two APIs for working with URLs: a legacy API that is\nNode.js specific, and a newer API that implements the same\nWHATWG URL Standard used by web browsers.
While the Legacy API has not been deprecated, it is maintained solely for\nbackwards compatibility with existing applications. New application code\nshould use the WHATWG API.
\nA comparison between the WHATWG and Legacy APIs is provided below. Above the URL\n'http://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash', properties\nof an object returned by the legacy url.parse() are shown. Below it are\nproperties of a WHATWG URL object.
WHATWG URL's origin property includes protocol and host, but not\nusername or password.
┌────────────────────────────────────────────────────────────────────────────────────────────────┐\n│ href │\n├──────────┬──┬─────────────────────┬────────────────────────┬───────────────────────────┬───────┤\n│ protocol │ │ auth │ host │ path │ hash │\n│ │ │ ├─────────────────┬──────┼──────────┬────────────────┤ │\n│ │ │ │ hostname │ port │ pathname │ search │ │\n│ │ │ │ │ │ ├─┬──────────────┤ │\n│ │ │ │ │ │ │ │ query │ │\n\" https: // user : pass @ sub.example.com : 8080 /p/a/t/h ? query=string #hash \"\n│ │ │ │ │ hostname │ port │ │ │ │\n│ │ │ │ ├─────────────────┴──────┤ │ │ │\n│ protocol │ │ username │ password │ host │ │ │ │\n├──────────┴──┼──────────┴──────────┼────────────────────────┤ │ │ │\n│ origin │ │ origin │ pathname │ search │ hash │\n├─────────────┴─────────────────────┴────────────────────────┴──────────┴────────────────┴───────┤\n│ href │\n└────────────────────────────────────────────────────────────────────────────────────────────────┘\n(all spaces in the \"\" line should be ignored — they are purely for formatting)\nParsing the URL string using the WHATWG API:
\nconst myURL =\n new URL('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\nParsing the URL string using the Legacy API:
\nconst url = require('url');\nconst myURL =\n url.parse('https://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash');\nBrowser-compatible URL class, implemented by following the WHATWG URL\nStandard. Examples of parsed URLs may be found in the Standard itself.\nThe URL class is also available on the global object.
In accordance with browser conventions, all properties of URL objects\nare implemented as getters and setters on the class prototype, rather than as\ndata properties on the object itself. Thus, unlike legacy urlObjects,\nusing the delete keyword on any properties of URL objects (e.g. delete myURL.protocol, delete myURL.pathname, etc) has no effect but will still\nreturn true.
Gets and sets the fragment portion of the URL.
\nconst myURL = new URL('https://example.org/foo#bar');\nconsole.log(myURL.hash);\n// Prints #bar\n\nmyURL.hash = 'baz';\nconsole.log(myURL.href);\n// Prints https://example.org/foo#baz\nInvalid URL characters included in the value assigned to the hash property\nare percent-encoded. Note that the selection of which characters to\npercent-encode may vary somewhat from what the url.parse() and\nurl.format() methods would produce.
Gets and sets the host portion of the URL.
\nconst myURL = new URL('https://example.org:81/foo');\nconsole.log(myURL.host);\n// Prints example.org:81\n\nmyURL.host = 'example.com:82';\nconsole.log(myURL.href);\n// Prints https://example.com:82/foo\nInvalid host values assigned to the host property are ignored.
Gets and sets the hostname portion of the URL. The key difference between\nurl.host and url.hostname is that url.hostname does not include the\nport.
const myURL = new URL('https://example.org:81/foo');\nconsole.log(myURL.hostname);\n// Prints example.org\n\nmyURL.hostname = 'example.com:82';\nconsole.log(myURL.href);\n// Prints https://example.com:81/foo\nInvalid hostname values assigned to the hostname property are ignored.
Gets and sets the serialized URL.
\nconst myURL = new URL('https://example.org/foo');\nconsole.log(myURL.href);\n// Prints https://example.org/foo\n\nmyURL.href = 'https://example.com/bar';\nconsole.log(myURL.href);\n// Prints https://example.com/bar\nGetting the value of the href property is equivalent to calling\nurl.toString().
Setting the value of this property to a new value is equivalent to creating a\nnew URL object using new URL(value). Each of the URL\nobject's properties will be modified.
If the value assigned to the href property is not a valid URL, a TypeError\nwill be thrown.
Gets the read-only serialization of the URL's origin.
\nconst myURL = new URL('https://example.org/foo/bar?baz');\nconsole.log(myURL.origin);\n// Prints https://example.org\nconst idnURL = new URL('https://測試');\nconsole.log(idnURL.origin);\n// Prints https://xn--g6w251d\n\nconsole.log(idnURL.hostname);\n// Prints xn--g6w251d\nGets and sets the password portion of the URL.
\nconst myURL = new URL('https://abc:xyz@example.com');\nconsole.log(myURL.password);\n// Prints xyz\n\nmyURL.password = '123';\nconsole.log(myURL.href);\n// Prints https://abc:123@example.com\nInvalid URL characters included in the value assigned to the password property\nare percent-encoded. Note that the selection of which characters to\npercent-encode may vary somewhat from what the url.parse() and\nurl.format() methods would produce.
Gets and sets the path portion of the URL.
\nconst myURL = new URL('https://example.org/abc/xyz?123');\nconsole.log(myURL.pathname);\n// Prints /abc/xyz\n\nmyURL.pathname = '/abcdef';\nconsole.log(myURL.href);\n// Prints https://example.org/abcdef?123\nInvalid URL characters included in the value assigned to the pathname\nproperty are percent-encoded. Note that the selection of which characters\nto percent-encode may vary somewhat from what the url.parse() and\nurl.format() methods would produce.
Gets and sets the port portion of the URL.
\nThe port value may be a number or a string containing a number in the range\n0 to 65535 (inclusive). Setting the value to the default port of the\nURL objects given protocol will result in the port value becoming\nthe empty string ('').
The port value can be an empty string in which case the port depends on\nthe protocol/scheme:
\n| protocol | \nport | \n
|---|---|
| \"ftp\" | \n21 | \n
| \"file\" | \n\n |
| \"gopher\" | \n70 | \n
| \"http\" | \n80 | \n
| \"https\" | \n443 | \n
| \"ws\" | \n80 | \n
| \"wss\" | \n443 | \n
Upon assigning a value to the port, the value will first be converted to a\nstring using .toString().
If that string is invalid but it begins with a number, the leading number is\nassigned to port.\nIf the number lies outside the range denoted above, it is ignored.
const myURL = new URL('https://example.org:8888');\nconsole.log(myURL.port);\n// Prints 8888\n\n// Default ports are automatically transformed to the empty string\n// (HTTPS protocol's default port is 443)\nmyURL.port = '443';\nconsole.log(myURL.port);\n// Prints the empty string\nconsole.log(myURL.href);\n// Prints https://example.org/\n\nmyURL.port = 1234;\nconsole.log(myURL.port);\n// Prints 1234\nconsole.log(myURL.href);\n// Prints https://example.org:1234/\n\n// Completely invalid port strings are ignored\nmyURL.port = 'abcd';\nconsole.log(myURL.port);\n// Prints 1234\n\n// Leading numbers are treated as a port number\nmyURL.port = '5678abcd';\nconsole.log(myURL.port);\n// Prints 5678\n\n// Non-integers are truncated\nmyURL.port = 1234.5678;\nconsole.log(myURL.port);\n// Prints 1234\n\n// Out-of-range numbers which are not represented in scientific notation\n// will be ignored.\nmyURL.port = 1e10; // 10000000000, will be range-checked as described below\nconsole.log(myURL.port);\n// Prints 1234\nNote that numbers which contain a decimal point,\nsuch as floating-point numbers or numbers in scientific notation,\nare not an exception to this rule.\nLeading numbers up to the decimal point will be set as the URL's port,\nassuming they are valid:
\nmyURL.port = 4.567e21;\nconsole.log(myURL.port);\n// Prints 4 (because it is the leading number in the string '4.567e21')\nGets and sets the protocol portion of the URL.
\nconst myURL = new URL('https://example.org');\nconsole.log(myURL.protocol);\n// Prints https:\n\nmyURL.protocol = 'ftp';\nconsole.log(myURL.href);\n// Prints ftp://example.org/\nInvalid URL protocol values assigned to the protocol property are ignored.
The WHATWG URL Standard considers a handful of URL protocol schemes to be\nspecial in terms of how they are parsed and serialized. When a URL is\nparsed using one of these special protocols, the url.protocol property\nmay be changed to another special protocol but cannot be changed to a\nnon-special protocol, and vice versa.
For instance, changing from http to https works:
const u = new URL('http://example.org');\nu.protocol = 'https';\nconsole.log(u.href);\n// https://example.org\nHowever, changing from http to a hypothetical fish protocol does not\nbecause the new protocol is not special.
const u = new URL('http://example.org');\nu.protocol = 'fish';\nconsole.log(u.href);\n// http://example.org\nLikewise, changing from a non-special protocol to a special protocol is also\nnot permitted:
\nconst u = new URL('fish://example.org');\nu.protocol = 'http';\nconsole.log(u.href);\n// fish://example.org\nThe protocol schemes considered to be special by the WHATWG URL Standard\ninclude: ftp, file, gopher, http, https, ws, and wss.
Gets and sets the serialized query portion of the URL.
\nconst myURL = new URL('https://example.org/abc?123');\nconsole.log(myURL.search);\n// Prints ?123\n\nmyURL.search = 'abc=xyz';\nconsole.log(myURL.href);\n// Prints https://example.org/abc?abc=xyz\nAny invalid URL characters appearing in the value assigned the search\nproperty will be percent-encoded. Note that the selection of which\ncharacters to percent-encode may vary somewhat from what the url.parse()\nand url.format() methods would produce.
Gets the URLSearchParams object representing the query parameters of the\nURL. This property is read-only; to replace the entirety of query parameters of\nthe URL, use the url.search setter. See URLSearchParams\ndocumentation for details.
Gets and sets the username portion of the URL.
\nconst myURL = new URL('https://abc:xyz@example.com');\nconsole.log(myURL.username);\n// Prints abc\n\nmyURL.username = '123';\nconsole.log(myURL.href);\n// Prints https://123:xyz@example.com/\nAny invalid URL characters appearing in the value assigned the username\nproperty will be percent-encoded. Note that the selection of which\ncharacters to percent-encode may vary somewhat from what the url.parse()\nand url.format() methods would produce.
The toString() method on the URL object returns the serialized URL. The\nvalue returned is equivalent to that of url.href and url.toJSON().
Because of the need for standard compliance, this method does not allow users\nto customize the serialization process of the URL. For more flexibility,\nrequire('url').format() method might be of interest.
The toJSON() method on the URL object returns the serialized URL. The\nvalue returned is equivalent to that of url.href and\nurl.toString().
This method is automatically called when an URL object is serialized\nwith JSON.stringify().
const myURLs = [\n new URL('https://www.example.com'),\n new URL('https://test.example.org')\n];\nconsole.log(JSON.stringify(myURLs));\n// Prints [\"https://www.example.com/\",\"https://test.example.org/\"]\nCreates a new URL object by parsing the input relative to the base. If\nbase is passed as a string, it will be parsed equivalent to new URL(base).
const myURL = new URL('/foo', 'https://example.org/');\n// https://example.org/foo\nA TypeError will be thrown if the input or base are not valid URLs. Note\nthat an effort will be made to coerce the given values into strings. For\ninstance:
const myURL = new URL({ toString: () => 'https://example.org/' });\n// https://example.org/\nUnicode characters appearing within the hostname of input will be\nautomatically converted to ASCII using the Punycode algorithm.
const myURL = new URL('https://測試');\n// https://xn--g6w251d/\nThis feature is only available if the node executable was compiled with\nICU enabled. If not, the domain names are passed through unchanged.
In cases where it is not known in advance if input is an absolute URL\nand a base is provided, it is advised to validate that the origin of\nthe URL object is what is expected.
let myURL = new URL('http://Example.com/', 'https://example.org/');\n// http://example.com/\n\nmyURL = new URL('https://Example.com/', 'https://example.org/');\n// https://example.com/\n\nmyURL = new URL('foo://Example.com/', 'https://example.org/');\n// foo://Example.com/\n\nmyURL = new URL('http:Example.com/', 'https://example.org/');\n// http://example.com/\n\nmyURL = new URL('https:Example.com/', 'https://example.org/');\n// https://example.org/Example.com/\n\nmyURL = new URL('foo:Example.com/', 'https://example.org/');\n// foo:Example.com/\nThe URLSearchParams API provides read and write access to the query of a\nURL. The URLSearchParams class can also be used standalone with one of the\nfour following constructors.\nThe URLSearchParams class is also available on the global object.
The WHATWG URLSearchParams interface and the querystring module have\nsimilar purpose, but the purpose of the querystring module is more\ngeneral, as it allows the customization of delimiter characters (& and =).\nOn the other hand, this API is designed purely for URL query strings.
const myURL = new URL('https://example.org/?abc=123');\nconsole.log(myURL.searchParams.get('abc'));\n// Prints 123\n\nmyURL.searchParams.append('abc', 'xyz');\nconsole.log(myURL.href);\n// Prints https://example.org/?abc=123&abc=xyz\n\nmyURL.searchParams.delete('abc');\nmyURL.searchParams.set('a', 'b');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b\n\nconst newSearchParams = new URLSearchParams(myURL.searchParams);\n// The above is equivalent to\n// const newSearchParams = new URLSearchParams(myURL.search);\n\nnewSearchParams.append('a', 'c');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b\nconsole.log(newSearchParams.toString());\n// Prints a=b&a=c\n\n// newSearchParams.toString() is implicitly called\nmyURL.search = newSearchParams;\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b&a=c\nnewSearchParams.delete('a');\nconsole.log(myURL.href);\n// Prints https://example.org/?a=b&a=c\nAppend a new name-value pair to the query string.
" }, { "textRaw": "urlSearchParams.delete(name)", "type": "method", "name": "delete", "signatures": [ { "params": [ { "textRaw": "`name` {string}", "name": "name", "type": "string" } ] } ], "desc": "Remove all name-value pairs whose name is name.
Returns an ES6 Iterator over each of the name-value pairs in the query.\nEach item of the iterator is a JavaScript Array. The first item of the Array\nis the name, the second item of the Array is the value.
Alias for urlSearchParams[@@iterator]().
Iterates over each name-value pair in the query and invokes the given function.
\nconst myURL = new URL('https://example.org/?a=b&c=d');\nmyURL.searchParams.forEach((value, name, searchParams) => {\n console.log(name, value, myURL.searchParams === searchParams);\n});\n// Prints:\n// a b true\n// c d true\nReturns the value of the first name-value pair whose name is name. If there\nare no such pairs, null is returned.
Returns the values of all name-value pairs whose name is name. If there are\nno such pairs, an empty array is returned.
Returns true if there is at least one name-value pair whose name is name.
Returns an ES6 Iterator over the names of each name-value pair.
const params = new URLSearchParams('foo=bar&foo=baz');\nfor (const name of params.keys()) {\n console.log(name);\n}\n// Prints:\n// foo\n// foo\nSets the value in the URLSearchParams object associated with name to\nvalue. If there are any pre-existing name-value pairs whose names are name,\nset the first such pair's value to value and remove all others. If not,\nappend the name-value pair to the query string.
const params = new URLSearchParams();\nparams.append('foo', 'bar');\nparams.append('foo', 'baz');\nparams.append('abc', 'def');\nconsole.log(params.toString());\n// Prints foo=bar&foo=baz&abc=def\n\nparams.set('foo', 'def');\nparams.set('xyz', 'opq');\nconsole.log(params.toString());\n// Prints foo=def&abc=def&xyz=opq\nSort all existing name-value pairs in-place by their names. Sorting is done\nwith a stable sorting algorithm, so relative order between name-value pairs\nwith the same name is preserved.
\nThis method can be used, in particular, to increase cache hits.
\nconst params = new URLSearchParams('query[]=abc&type=search&query[]=123');\nparams.sort();\nconsole.log(params.toString());\n// Prints query%5B%5D=abc&query%5B%5D=123&type=search\nReturns the search parameters serialized as a string, with characters\npercent-encoded where necessary.
" }, { "textRaw": "urlSearchParams.values()", "type": "method", "name": "values", "signatures": [ { "return": { "textRaw": "Returns: {Iterator}", "name": "return", "type": "Iterator" }, "params": [] } ], "desc": "Returns an ES6 Iterator over the values of each name-value pair.
Returns an ES6 Iterator over each of the name-value pairs in the query string.\nEach item of the iterator is a JavaScript Array. The first item of the Array\nis the name, the second item of the Array is the value.
Alias for urlSearchParams.entries().
const params = new URLSearchParams('foo=bar&xyz=baz');\nfor (const [name, value] of params) {\n console.log(name, value);\n}\n// Prints:\n// foo bar\n// xyz baz\nInstantiate a new empty URLSearchParams object.
Parse the string as a query string, and use it to instantiate a new\nURLSearchParams object. A leading '?', if present, is ignored.
let params;\n\nparams = new URLSearchParams('user=abc&query=xyz');\nconsole.log(params.get('user'));\n// Prints 'abc'\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\n\nparams = new URLSearchParams('?user=abc&query=xyz');\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\nInstantiate a new URLSearchParams object with a query hash map. The key and\nvalue of each property of obj are always coerced to strings.
Unlike querystring module, duplicate keys in the form of array values are\nnot allowed. Arrays are stringified using array.toString(), which simply\njoins all array elements with commas.
const params = new URLSearchParams({\n user: 'abc',\n query: ['first', 'second']\n});\nconsole.log(params.getAll('query'));\n// Prints [ 'first,second' ]\nconsole.log(params.toString());\n// Prints 'user=abc&query=first%2Csecond'\nInstantiate a new URLSearchParams object with an iterable map in a way that\nis similar to Map's constructor. iterable can be an Array or any\niterable object. That means iterable can be another URLSearchParams, in\nwhich case the constructor will simply create a clone of the provided\nURLSearchParams. Elements of iterable are key-value pairs, and can\nthemselves be any iterable object.
Duplicate keys are allowed.
\nlet params;\n\n// Using an array\nparams = new URLSearchParams([\n ['user', 'abc'],\n ['query', 'first'],\n ['query', 'second']\n]);\nconsole.log(params.toString());\n// Prints 'user=abc&query=first&query=second'\n\n// Using a Map object\nconst map = new Map();\nmap.set('user', 'abc');\nmap.set('query', 'xyz');\nparams = new URLSearchParams(map);\nconsole.log(params.toString());\n// Prints 'user=abc&query=xyz'\n\n// Using a generator function\nfunction* getQueryPairs() {\n yield ['user', 'abc'];\n yield ['query', 'first'];\n yield ['query', 'second'];\n}\nparams = new URLSearchParams(getQueryPairs());\nconsole.log(params.toString());\n// Prints 'user=abc&query=first&query=second'\n\n// Each key-value pair must have exactly two elements\nnew URLSearchParams([\n ['user', 'abc', 'error']\n]);\n// Throws TypeError [ERR_INVALID_TUPLE]:\n// Each query pair must be an iterable [name, value] tuple\nReturns the Punycode ASCII serialization of the domain. If domain is an\ninvalid domain, the empty string is returned.
It performs the inverse operation to url.domainToUnicode().
const url = require('url');\nconsole.log(url.domainToASCII('español.com'));\n// Prints xn--espaol-zwa.com\nconsole.log(url.domainToASCII('中文.com'));\n// Prints xn--fiq228c.com\nconsole.log(url.domainToASCII('xn--iñvalid.com'));\n// Prints an empty string\nReturns the Unicode serialization of the domain. If domain is an invalid\ndomain, the empty string is returned.
It performs the inverse operation to url.domainToASCII().
const url = require('url');\nconsole.log(url.domainToUnicode('xn--espaol-zwa.com'));\n// Prints español.com\nconsole.log(url.domainToUnicode('xn--fiq228c.com'));\n// Prints 中文.com\nconsole.log(url.domainToUnicode('xn--iñvalid.com'));\n// Prints an empty string\nThis function ensures the correct decodings of percent-encoded characters as\nwell as ensuring a cross-platform valid absolute path string.
\nnew URL('file:///C:/path/').pathname; // Incorrect: /C:/path/\nfileURLToPath('file:///C:/path/'); // Correct: C:\\path\\ (Windows)\n\nnew URL('file://nas/foo.txt').pathname; // Incorrect: /foo.txt\nfileURLToPath('file://nas/foo.txt'); // Correct: \\\\nas\\foo.txt (Windows)\n\nnew URL('file:///你好.txt').pathname; // Incorrect: /%E4%BD%A0%E5%A5%BD.txt\nfileURLToPath('file:///你好.txt'); // Correct: /你好.txt (POSIX)\n\nnew URL('file:///hello world').pathname; // Incorrect: /hello%20world\nfileURLToPath('file:///hello world'); // Correct: /hello world (POSIX)\nReturns a customizable serialization of a URL String representation of a\nWHATWG URL object.
The URL object has both a toString() method and href property that return\nstring serializations of the URL. These are not, however, customizable in\nany way. The url.format(URL[, options]) method allows for basic customization\nof the output.
const myURL = new URL('https://a:b@測試?abc#foo');\n\nconsole.log(myURL.href);\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(myURL.toString());\n// Prints https://a:b@xn--g6w251d/?abc#foo\n\nconsole.log(url.format(myURL, { fragment: false, unicode: true, auth: false }));\n// Prints 'https://測試/?abc'\nThis function ensures that path is resolved absolutely, and that the URL\ncontrol characters are correctly encoded when converting into a File URL.
new URL(__filename); // Incorrect: throws (POSIX)\nnew URL(__filename); // Incorrect: C:\\... (Windows)\npathToFileURL(__filename); // Correct: file:///... (POSIX)\npathToFileURL(__filename); // Correct: file:///C:/... (Windows)\n\nnew URL('/foo#1', 'file:'); // Incorrect: file:///foo#1\npathToFileURL('/foo#1'); // Correct: file:///foo%231 (POSIX)\n\nnew URL('/some/path%.js', 'file:'); // Incorrect: file:///some/path%\npathToFileURL('/some/path%.js'); // Correct: file:///some/path%25 (POSIX)\nThe legacy urlObject (require('url').Url) is created and returned by the\nurl.parse() function.
The auth property is the username and password portion of the URL, also\nreferred to as userinfo. This string subset follows the protocol and\ndouble slashes (if present) and precedes the host component, delimited by @.\nThe string is either the username, or it is the username and password separated\nby :.
For example: 'user:pass'.
The hash property is the fragment identifier portion of the URL including the\nleading # character.
For example: '#hash'.
The host property is the full lower-cased host portion of the URL, including\nthe port if specified.
For example: 'sub.example.com:8080'.
The hostname property is the lower-cased host name portion of the host\ncomponent without the port included.
For example: 'sub.example.com'.
The href property is the full URL string that was parsed with both the\nprotocol and host components converted to lower-case.
For example: 'http://user:pass@sub.example.com:8080/p/a/t/h?query=string#hash'.
The path property is a concatenation of the pathname and search\ncomponents.
For example: '/p/a/t/h?query=string'.
No decoding of the path is performed.
The pathname property consists of the entire path section of the URL. This\nis everything following the host (including the port) and before the start\nof the query or hash components, delimited by either the ASCII question\nmark (?) or hash (#) characters.
For example: '/p/a/t/h'.
No decoding of the path string is performed.
" }, { "textRaw": "urlObject.port", "name": "port", "desc": "The port property is the numeric port portion of the host component.
For example: '8080'.
The protocol property identifies the URL's lower-cased protocol scheme.
For example: 'http:'.
The query property is either the query string without the leading ASCII\nquestion mark (?), or an object returned by the querystring module's\nparse() method. Whether the query property is a string or object is\ndetermined by the parseQueryString argument passed to url.parse().
For example: 'query=string' or {'query': 'string'}.
If returned as a string, no decoding of the query string is performed. If\nreturned as an object, both keys and values are decoded.
" }, { "textRaw": "urlObject.search", "name": "search", "desc": "The search property consists of the entire \"query string\" portion of the\nURL, including the leading ASCII question mark (?) character.
For example: '?query=string'.
No decoding of the query string is performed.
" }, { "textRaw": "urlObject.slashes", "name": "slashes", "desc": "The slashes property is a boolean with a value of true if two ASCII\nforward-slash characters (/) are required following the colon in the\nprotocol.
The url.format() method returns a formatted URL string derived from\nurlObject.
url.format({\n protocol: 'https',\n hostname: 'example.com',\n pathname: '/some/path',\n query: {\n page: 1,\n format: 'json'\n }\n});\n\n// => 'https://example.com/some/path?page=1&format=json'\nIf urlObject is not an object or a string, url.format() will throw a\nTypeError.
The formatting process operates as follows:
\nresult is created.urlObject.protocol is a string, it is appended as-is to result.urlObject.protocol is not undefined and is not a string, an\nError is thrown.urlObject.protocol that do not end with an ASCII\ncolon (:) character, the literal string : will be appended to result.If either of the following conditions is true, then the literal string //\nwill be appended to result:
urlObject.slashes property is true;urlObject.protocol begins with http, https, ftp, gopher, or\nfile;urlObject.auth property is truthy, and either\nurlObject.host or urlObject.hostname are not undefined, the value of\nurlObject.auth will be coerced into a string and appended to result\nfollowed by the literal string @.If the urlObject.host property is undefined then:
urlObject.hostname is a string, it is appended to result.urlObject.hostname is not undefined and is not a string,\nan Error is thrown.If the urlObject.port property value is truthy, and urlObject.hostname\nis not undefined:
: is appended to result, andurlObject.port is coerced to a string and appended to\nresult.urlObject.host property value is truthy, the value of\nurlObject.host is coerced to a string and appended to result.If the urlObject.pathname property is a string that is not an empty string:
urlObject.pathname does not start with an ASCII forward slash\n(/), then the literal string '/' is appended to result.urlObject.pathname is appended to result.urlObject.pathname is not undefined and is not a string, an\nError is thrown.urlObject.search property is undefined and if the urlObject.query\nproperty is an Object, the literal string ? is appended to result\nfollowed by the output of calling the querystring module's stringify()\nmethod passing the value of urlObject.query.Otherwise, if urlObject.search is a string:
urlObject.search does not start with the ASCII question\nmark (?) character, the literal string ? is appended to result.urlObject.search is appended to result.urlObject.search is not undefined and is not a string, an\nError is thrown.If the urlObject.hash property is a string:
urlObject.hash does not start with the ASCII hash (#)\ncharacter, the literal string # is appended to result.urlObject.hash is appended to result.urlObject.hash property is not undefined and is not a\nstring, an Error is thrown.result is returned.The url.parse() method takes a URL string, parses it, and returns a URL\nobject.
A TypeError is thrown if urlString is not a string.
A URIError is thrown if the auth property is present but cannot be decoded.
The url.resolve() method resolves a target URL relative to a base URL in a\nmanner similar to that of a Web browser resolving an anchor tag HREF.
const url = require('url');\nurl.resolve('/one/two/three', 'four'); // '/one/two/four'\nurl.resolve('http://example.com/', '/one'); // 'http://example.com/one'\nurl.resolve('http://example.com/one', '/two'); // 'http://example.com/two'\nURLs are permitted to only contain a certain range of characters. Any character\nfalling outside of that range must be encoded. How such characters are encoded,\nand which characters to encode depends entirely on where the character is\nlocated within the structure of the URL.
", "modules": [ { "textRaw": "Legacy API", "name": "legacy_api", "desc": "Within the Legacy API, spaces (' ') and the following characters will be\nautomatically escaped in the properties of URL objects:
< > \" ` \\r \\n \\t { } | \\ ^ '\nFor example, the ASCII space character (' ') is encoded as %20. The ASCII\nforward slash (/) character is encoded as %3C.
The WHATWG URL Standard uses a more selective and fine grained approach to\nselecting encoded characters than that used by the Legacy API.
\nThe WHATWG algorithm defines four \"percent-encode sets\" that describe ranges\nof characters that must be percent-encoded:
\nThe C0 control percent-encode set includes code points in range U+0000 to\nU+001F (inclusive) and all code points greater than U+007E.
\nThe fragment percent-encode set includes the C0 control percent-encode set\nand code points U+0020, U+0022, U+003C, U+003E, and U+0060.
\nThe path percent-encode set includes the C0 control percent-encode set\nand code points U+0020, U+0022, U+0023, U+003C, U+003E, U+003F, U+0060,\nU+007B, and U+007D.
\nThe userinfo encode set includes the path percent-encode set and code\npoints U+002F, U+003A, U+003B, U+003D, U+0040, U+005B, U+005C, U+005D,\nU+005E, and U+007C.
\nThe userinfo percent-encode set is used exclusively for username and\npasswords encoded within the URL. The path percent-encode set is used for the\npath of most URLs. The fragment percent-encode set is used for URL fragments.\nThe C0 control percent-encode set is used for host and path under certain\nspecific conditions, in addition to all other cases.
\nWhen non-ASCII characters appear within a hostname, the hostname is encoded\nusing the Punycode algorithm. Note, however, that a hostname may contain\nboth Punycode encoded and percent-encoded characters:
\nconst myURL = new URL('https://%CF%80.example.com/foo');\nconsole.log(myURL.href);\n// Prints https://xn--1xa.example.com/foo\nconsole.log(myURL.origin);\n// Prints https://xn--1xa.example.com\nThe util module is primarily designed to support the needs of Node.js' own\ninternal APIs. However, many of the utilities are useful for application and\nmodule developers as well. It can be accessed using:
const util = require('util');\nTakes an async function (or a function that returns a Promise) and returns a\nfunction following the error-first callback style, i.e. taking\nan (err, value) => ... callback as the last argument. In the callback, the\nfirst argument will be the rejection reason (or null if the Promise\nresolved), and the second argument will be the resolved value.
const util = require('util');\n\nasync function fn() {\n return 'hello world';\n}\nconst callbackFunction = util.callbackify(fn);\n\ncallbackFunction((err, ret) => {\n if (err) throw err;\n console.log(ret);\n});\nWill print:
\nhello world\nThe callback is executed asynchronously, and will have a limited stack trace.\nIf the callback throws, the process will emit an 'uncaughtException'\nevent, and if not handled will exit.
Since null has a special meaning as the first argument to a callback, if a\nwrapped function rejects a Promise with a falsy value as a reason, the value\nis wrapped in an Error with the original value stored in a field named\nreason.
function fn() {\n return Promise.reject(null);\n}\nconst callbackFunction = util.callbackify(fn);\n\ncallbackFunction((err, ret) => {\n // When the Promise was rejected with `null` it is wrapped with an Error and\n // the original value is stored in `reason`.\n err && err.hasOwnProperty('reason') && err.reason === null; // true\n});\nThe util.debuglog() method is used to create a function that conditionally\nwrites debug messages to stderr based on the existence of the NODE_DEBUG\nenvironment variable. If the section name appears within the value of that\nenvironment variable, then the returned function operates similar to\nconsole.error(). If not, then the returned function is a no-op.
const util = require('util');\nconst debuglog = util.debuglog('foo');\n\ndebuglog('hello from foo [%d]', 123);\nIf this program is run with NODE_DEBUG=foo in the environment, then\nit will output something like:
FOO 3245: hello from foo [123]\nwhere 3245 is the process id. If it is not run with that\nenvironment variable set, then it will not print anything.
The section supports wildcard also:
const util = require('util');\nconst debuglog = util.debuglog('foo-bar');\n\ndebuglog('hi there, it\\'s foo-bar [%d]', 2333);\nif it is run with NODE_DEBUG=foo* in the environment, then it will output\nsomething like:
FOO-BAR 3257: hi there, it's foo-bar [2333]\nMultiple comma-separated section names may be specified in the NODE_DEBUG\nenvironment variable: NODE_DEBUG=fs,net,tls.
The util.deprecate() method wraps fn (which may be a function or class) in\nsuch a way that it is marked as deprecated.
const util = require('util');\n\nexports.obsoleteFunction = util.deprecate(() => {\n // Do something here.\n}, 'obsoleteFunction() is deprecated. Use newShinyFunction() instead.');\nWhen called, util.deprecate() will return a function that will emit a\nDeprecationWarning using the 'warning' event. The warning will\nbe emitted and printed to stderr the first time the returned function is\ncalled. After the warning is emitted, the wrapped function is called without\nemitting a warning.
If the same optional code is supplied in multiple calls to util.deprecate(),\nthe warning will be emitted only once for that code.
const util = require('util');\n\nconst fn1 = util.deprecate(someFunction, someMessage, 'DEP0001');\nconst fn2 = util.deprecate(someOtherFunction, someOtherMessage, 'DEP0001');\nfn1(); // emits a deprecation warning with code DEP0001\nfn2(); // does not emit a deprecation warning because it has the same code\nIf either the --no-deprecation or --no-warnings command line flags are\nused, or if the process.noDeprecation property is set to true prior to\nthe first deprecation warning, the util.deprecate() method does nothing.
If the --trace-deprecation or --trace-warnings command line flags are set,\nor the process.traceDeprecation property is set to true, a warning and a\nstack trace are printed to stderr the first time the deprecated function is\ncalled.
If the --throw-deprecation command line flag is set, or the\nprocess.throwDeprecation property is set to true, then an exception will be\nthrown when the deprecated function is called.
The --throw-deprecation command line flag and process.throwDeprecation\nproperty take precedence over --trace-deprecation and\nprocess.traceDeprecation.
The util.format() method returns a formatted string using the first argument\nas a printf-like format.
The first argument is a string containing zero or more placeholder tokens.\nEach placeholder token is replaced with the converted value from the\ncorresponding argument. Supported placeholders are:
\n%s - String.%d - Number (integer or floating point value) or BigInt.%i - Integer or BigInt.%f - Floating point value.%j - JSON. Replaced with the string '[Circular]' if the argument\ncontains circular references.%o - Object. A string representation of an object\nwith generic JavaScript object formatting.\nSimilar to util.inspect() with options\n{ showHidden: true, showProxy: true }. This will show the full object\nincluding non-enumerable properties and proxies.%O - Object. A string representation of an object with generic JavaScript\nobject formatting. Similar to util.inspect() without options. This will show\nthe full object not including non-enumerable properties and proxies.%% - single percent sign ('%'). This does not consume an argument.If the placeholder does not have a corresponding argument, the placeholder is\nnot replaced.
\nutil.format('%s:%s', 'foo');\n// Returns: 'foo:%s'\nIf there are more arguments passed to the util.format() method than the number\nof placeholders, the extra arguments are coerced into strings then concatenated\nto the returned string, each delimited by a space. Excessive arguments whose\ntypeof is 'object' or 'symbol' (except null) will be transformed by\nutil.inspect().
util.format('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'\nIf the first argument is not a string then util.format() returns\na string that is the concatenation of all arguments separated by spaces.\nEach argument is converted to a string using util.inspect().
util.format(1, 2, 3); // '1 2 3'\nIf only one argument is passed to util.format(), it is returned as it is\nwithout any formatting.
util.format('%% %s'); // '%% %s'\nPlease note that util.format() is a synchronous method that is mainly\nintended as a debugging tool. Some input values can have a significant\nperformance overhead that can block the event loop. Use this function\nwith care and never in a hot code path.
This function is identical to util.format(), except in that it takes\nan inspectOptions argument which specifies options that are passed along to\nutil.inspect().
util.formatWithOptions({ colors: true }, 'See object %O', { foo: 42 });\n// Returns 'See object { foo: 42 }', where `42` is colored as a number\n// when printed to a terminal.\nReturns the string name for a numeric error code that comes from a Node.js API.\nThe mapping between error codes and error names is platform-dependent.\nSee Common System Errors for the names of common errors.
\nfs.access('file/that/does/not/exist', (err) => {\n const name = util.getSystemErrorName(err.errno);\n console.error(name); // ENOENT\n});\nUsage of util.inherits() is discouraged. Please use the ES6 class and\nextends keywords to get language level inheritance support. Also note\nthat the two styles are semantically incompatible.
Inherit the prototype methods from one constructor into another. The\nprototype of constructor will be set to a new object created from\nsuperConstructor.
As an additional convenience, superConstructor will be accessible\nthrough the constructor.super_ property.
const util = require('util');\nconst EventEmitter = require('events');\n\nfunction MyStream() {\n EventEmitter.call(this);\n}\n\nutil.inherits(MyStream, EventEmitter);\n\nMyStream.prototype.write = function(data) {\n this.emit('data', data);\n};\n\nconst stream = new MyStream();\n\nconsole.log(stream instanceof EventEmitter); // true\nconsole.log(MyStream.super_ === EventEmitter); // true\n\nstream.on('data', (data) => {\n console.log(`Received data: \"${data}\"`);\n});\nstream.write('It works!'); // Received data: \"It works!\"\nES6 example using class and extends:
const EventEmitter = require('events');\n\nclass MyStream extends EventEmitter {\n write(data) {\n this.emit('data', data);\n }\n}\n\nconst stream = new MyStream();\n\nstream.on('data', (data) => {\n console.log(`Received data: \"${data}\"`);\n});\nstream.write('With ES6');\nThe util.inspect() method returns a string representation of object that is\nintended for debugging. The output of util.inspect may change at any time\nand should not be depended upon programmatically. Additional options may be\npassed that alter certain aspects of the formatted string.\nutil.inspect() will use the constructor's name and/or @@toStringTag to make\nan identifiable tag for an inspected value.
class Foo {\n get [Symbol.toStringTag]() {\n return 'bar';\n }\n}\n\nclass Bar {}\n\nconst baz = Object.create(null, { [Symbol.toStringTag]: { value: 'foo' } });\n\nutil.inspect(new Foo()); // 'Foo [bar] {}'\nutil.inspect(new Bar()); // 'Bar {}'\nutil.inspect(baz); // '[foo] {}'\nThe following example inspects all properties of the util object:
const util = require('util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\nValues may supply their own custom inspect(depth, opts) functions, when\ncalled these receive the current depth in the recursive inspection, as well as\nthe options object passed to util.inspect().
The following example highlights the difference with the compact option:
const util = require('util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ' +\n 'eiusmod tempor incididunt ut labore et dolore magna aliqua.',\n 'test',\n 'foo']], 4],\n b: new Map([['za', 1], ['zb', 'test']])\n};\nconsole.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));\n\n// This will print\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false changes the output to be more reader friendly.\nconsole.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));\n\n// {\n// a: [\n// 1,\n// 2,\n// [\n// [\n// 'Lorem ipsum dolor sit amet, consectetur ' +\n// 'adipiscing elit, sed do eiusmod tempor ' +\n// 'incididunt ut labore et dolore magna ' +\n// 'aliqua.,\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map {\n// 'za' => 1,\n// 'zb' => 'test'\n// }\n// }\n\n// Setting `breakLength` to e.g. 150 will print the \"Lorem ipsum\" text in a\n// single line.\n// Reducing the `breakLength` will split the \"Lorem ipsum\" text in smaller\n// chunks.\nUsing the showHidden option allows to inspect WeakMap and WeakSet\nentries. If there are more entries than maxArrayLength, there is no guarantee\nwhich entries are displayed. That means retrieving the same WeakSet\nentries twice might actually result in a different output. Besides this any item\nmight be collected at any point of time by the garbage collector if there is no\nstrong reference left to that object. Therefore there is no guarantee to get a\nreliable output.
const { inspect } = require('util');\n\nconst obj = { a: 1 };\nconst obj2 = { b: 2 };\nconst weakSet = new WeakSet([obj, obj2]);\n\nconsole.log(inspect(weakSet, { showHidden: true }));\n// WeakSet { { a: 1 }, { b: 2 } }\nThe sorted option makes sure the output is identical, no matter of the\nproperties insertion order:
const { inspect } = require('util');\nconst assert = require('assert');\n\nconst o1 = {\n b: [2, 3, 1],\n a: '`a` comes before `b`',\n c: new Set([2, 3, 1])\n};\nconsole.log(inspect(o1, { sorted: true }));\n// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }\n\nconst o2 = {\n c: new Set([2, 1, 3]),\n a: '`a` comes before `b`',\n b: [2, 3, 1]\n};\nassert.strict.equal(\n inspect(o1, { sorted: true }),\n inspect(o2, { sorted: true })\n);\nPlease note that util.inspect() is a synchronous method that is mainly\nintended as a debugging tool. Some input values can have a significant\nperformance overhead that can block the event loop. Use this function\nwith care and never in a hot code path.
The util.inspect() method returns a string representation of object that is\nintended for debugging. The output of util.inspect may change at any time\nand should not be depended upon programmatically. Additional options may be\npassed that alter certain aspects of the formatted string.\nutil.inspect() will use the constructor's name and/or @@toStringTag to make\nan identifiable tag for an inspected value.
class Foo {\n get [Symbol.toStringTag]() {\n return 'bar';\n }\n}\n\nclass Bar {}\n\nconst baz = Object.create(null, { [Symbol.toStringTag]: { value: 'foo' } });\n\nutil.inspect(new Foo()); // 'Foo [bar] {}'\nutil.inspect(new Bar()); // 'Bar {}'\nutil.inspect(baz); // '[foo] {}'\nThe following example inspects all properties of the util object:
const util = require('util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));\nValues may supply their own custom inspect(depth, opts) functions, when\ncalled these receive the current depth in the recursive inspection, as well as\nthe options object passed to util.inspect().
The following example highlights the difference with the compact option:
const util = require('util');\n\nconst o = {\n a: [1, 2, [[\n 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ' +\n 'eiusmod tempor incididunt ut labore et dolore magna aliqua.',\n 'test',\n 'foo']], 4],\n b: new Map([['za', 1], ['zb', 'test']])\n};\nconsole.log(util.inspect(o, { compact: true, depth: 5, breakLength: 80 }));\n\n// This will print\n\n// { a:\n// [ 1,\n// 2,\n// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line\n// 'test',\n// 'foo' ] ],\n// 4 ],\n// b: Map { 'za' => 1, 'zb' => 'test' } }\n\n// Setting `compact` to false changes the output to be more reader friendly.\nconsole.log(util.inspect(o, { compact: false, depth: 5, breakLength: 80 }));\n\n// {\n// a: [\n// 1,\n// 2,\n// [\n// [\n// 'Lorem ipsum dolor sit amet, consectetur ' +\n// 'adipiscing elit, sed do eiusmod tempor ' +\n// 'incididunt ut labore et dolore magna ' +\n// 'aliqua.,\n// 'test',\n// 'foo'\n// ]\n// ],\n// 4\n// ],\n// b: Map {\n// 'za' => 1,\n// 'zb' => 'test'\n// }\n// }\n\n// Setting `breakLength` to e.g. 150 will print the \"Lorem ipsum\" text in a\n// single line.\n// Reducing the `breakLength` will split the \"Lorem ipsum\" text in smaller\n// chunks.\nUsing the showHidden option allows to inspect WeakMap and WeakSet\nentries. If there are more entries than maxArrayLength, there is no guarantee\nwhich entries are displayed. That means retrieving the same WeakSet\nentries twice might actually result in a different output. Besides this any item\nmight be collected at any point of time by the garbage collector if there is no\nstrong reference left to that object. Therefore there is no guarantee to get a\nreliable output.
const { inspect } = require('util');\n\nconst obj = { a: 1 };\nconst obj2 = { b: 2 };\nconst weakSet = new WeakSet([obj, obj2]);\n\nconsole.log(inspect(weakSet, { showHidden: true }));\n// WeakSet { { a: 1 }, { b: 2 } }\nThe sorted option makes sure the output is identical, no matter of the\nproperties insertion order:
const { inspect } = require('util');\nconst assert = require('assert');\n\nconst o1 = {\n b: [2, 3, 1],\n a: '`a` comes before `b`',\n c: new Set([2, 3, 1])\n};\nconsole.log(inspect(o1, { sorted: true }));\n// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set { 1, 2, 3 } }\nconsole.log(inspect(o1, { sorted: (a, b) => b.localeCompare(a) }));\n// { c: Set { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }\n\nconst o2 = {\n c: new Set([2, 1, 3]),\n a: '`a` comes before `b`',\n b: [2, 3, 1]\n};\nassert.strict.equal(\n inspect(o1, { sorted: true }),\n inspect(o2, { sorted: true })\n);\nPlease note that util.inspect() is a synchronous method that is mainly\nintended as a debugging tool. Some input values can have a significant\nperformance overhead that can block the event loop. Use this function\nwith care and never in a hot code path.
Color output (if enabled) of util.inspect is customizable globally\nvia the util.inspect.styles and util.inspect.colors properties.
util.inspect.styles is a map associating a style name to a color from\nutil.inspect.colors.
The default styles and associated colors are:
\nnumber - yellowboolean - yellowstring - greendate - magentaregexp - rednull - boldundefined - greyspecial - cyan (only applied to functions at this time)name - (no styling)The predefined color codes are: white, grey, black, blue, cyan,\ngreen, magenta, red and yellow. There are also bold, italic,\nunderline and inverse codes.
Color styling uses ANSI control codes that may not be supported on all\nterminals.
" }, { "textRaw": "Custom inspection functions on Objects", "name": "Custom inspection functions on Objects", "type": "misc", "desc": "Objects may also define their own\n[util.inspect.custom](depth, opts) (or the equivalent\nbut deprecated inspect(depth, opts)) function, which util.inspect() will\ninvoke and use the result of when inspecting the object:
const util = require('util');\n\nclass Box {\n constructor(value) {\n this.value = value;\n }\n\n [util.inspect.custom](depth, options) {\n if (depth < 0) {\n return options.stylize('[Box]', 'special');\n }\n\n const newOptions = Object.assign({}, options, {\n depth: options.depth === null ? null : options.depth - 1\n });\n\n // Five space padding because that's the size of \"Box< \".\n const padding = ' '.repeat(5);\n const inner = util.inspect(this.value, newOptions)\n .replace(/\\n/g, `\\n${padding}`);\n return `${options.stylize('Box', 'special')}< ${inner} >`;\n }\n}\n\nconst box = new Box(true);\n\nutil.inspect(box);\n// Returns: \"Box< true >\"\nCustom [util.inspect.custom](depth, opts) functions typically return a string\nbut may return a value of any type that will be formatted accordingly by\nutil.inspect().
const util = require('util');\n\nconst obj = { foo: 'this will not show up in the inspect() output' };\nobj[util.inspect.custom] = (depth) => {\n return { bar: 'baz' };\n};\n\nutil.inspect(obj);\n// Returns: \"{ bar: 'baz' }\"\nIn addition to being accessible through util.inspect.custom, this\nsymbol is registered globally and can be\naccessed in any environment as Symbol.for('nodejs.util.inspect.custom').
const inspect = Symbol.for('nodejs.util.inspect.custom');\n\nclass Password {\n constructor(value) {\n this.value = value;\n }\n\n toString() {\n return 'xxxxxxxx';\n }\n\n [inspect]() {\n return `Password <${this.toString()}>`;\n }\n}\n\nconst password = new Password('r0sebud');\nconsole.log(password);\n// Prints Password <xxxxxxxx>\nSee Custom inspection functions on Objects for more details.
", "shortDesc": "that can be used to declare custom inspect functions." }, { "textRaw": "util.inspect.defaultOptions", "name": "defaultOptions", "meta": { "added": [ "v6.4.0" ], "changes": [] }, "desc": "The defaultOptions value allows customization of the default options used by\nutil.inspect. This is useful for functions like console.log or\nutil.format which implicitly call into util.inspect. It shall be set to an\nobject containing one or more valid util.inspect() options. Setting\noption properties directly is also supported.
const util = require('util');\nconst arr = Array(101).fill(0);\n\nconsole.log(arr); // logs the truncated array\nutil.inspect.defaultOptions.maxArrayLength = null;\nconsole.log(arr); // logs the full array\nReturns true if there is deep strict equality between val1 and val2.\nOtherwise, returns false.
See assert.deepStrictEqual() for more information about deep strict\nequality.
Takes a function following the common error-first callback style, i.e. taking\nan (err, value) => ... callback as the last argument, and returns a version\nthat returns promises.
const util = require('util');\nconst fs = require('fs');\n\nconst stat = util.promisify(fs.stat);\nstat('.').then((stats) => {\n // Do something with `stats`\n}).catch((error) => {\n // Handle the error.\n});\nOr, equivalently using async functions:
const util = require('util');\nconst fs = require('fs');\n\nconst stat = util.promisify(fs.stat);\n\nasync function callStat() {\n const stats = await stat('.');\n console.log(`This directory is owned by ${stats.uid}`);\n}\nIf there is an original[util.promisify.custom] property present, promisify\nwill return its value, see Custom promisified functions.
promisify() assumes that original is a function taking a callback as its\nfinal argument in all cases. If original is not a function, promisify()\nwill throw an error. If original is a function but its last argument is not\nan error-first callback, it will still be passed an error-first\ncallback as its last argument.
Using the util.promisify.custom symbol one can override the return value of\nutil.promisify():
const util = require('util');\n\nfunction doSomething(foo, callback) {\n // ...\n}\n\ndoSomething[util.promisify.custom] = (foo) => {\n return getPromiseSomehow();\n};\n\nconst promisified = util.promisify(doSomething);\nconsole.log(promisified === doSomething[util.promisify.custom]);\n// prints 'true'\nThis can be useful for cases where the original function does not follow the\nstandard format of taking an error-first callback as the last argument.
\nFor example, with a function that takes in\n(foo, onSuccessCallback, onErrorCallback):
doSomething[util.promisify.custom] = (foo) => {\n return new Promise((resolve, reject) => {\n doSomething(foo, resolve, reject);\n });\n};\nIf promisify.custom is defined but is not a function, promisify() will\nthrow an error.
A <symbol> that can be used to declare custom promisified variants of functions,\nsee Custom promisified functions.
" } ] } ], "classes": [ { "textRaw": "Class: util.TextDecoder", "type": "class", "name": "util.TextDecoder", "meta": { "added": [ "v8.3.0" ], "changes": [] }, "desc": "An implementation of the WHATWG Encoding Standard TextDecoder API.
const decoder = new TextDecoder('shift_jis');\nlet string = '';\nlet buffer;\nwhile (buffer = getNextChunkSomehow()) {\n string += decoder.decode(buffer, { stream: true });\n}\nstring += decoder.decode(); // end-of-stream\nPer the WHATWG Encoding Standard, the encodings supported by the\nTextDecoder API are outlined in the tables below. For each encoding,\none or more aliases may be used.
Different Node.js build configurations support different sets of encodings.\nWhile a very basic set of encodings is supported even on Node.js builds without\nICU enabled, support for some encodings is provided only when Node.js is built\nwith ICU and using the full ICU data (see Internationalization).
", "modules": [ { "textRaw": "Encodings Supported Without ICU", "name": "encodings_supported_without_icu", "desc": "| Encoding | \nAliases | \n
|---|---|
'utf-8' | \n'unicode-1-1-utf-8', 'utf8' | \n
'utf-16le' | \n'utf-16' | \n
| Encoding | \nAliases | \n
|---|---|
'utf-8' | \n'unicode-1-1-utf-8', 'utf8' | \n
'utf-16le' | \n'utf-16' | \n
'utf-16be' | \n\n |
| Encoding | \nAliases | \n
|---|---|
'ibm866' | \n'866', 'cp866', 'csibm866' | \n
'iso-8859-2' | \n'csisolatin2', 'iso-ir-101', 'iso8859-2', 'iso88592', 'iso_8859-2', 'iso_8859-2:1987', 'l2', 'latin2' | \n
'iso-8859-3' | \n'csisolatin3', 'iso-ir-109', 'iso8859-3', 'iso88593', 'iso_8859-3', 'iso_8859-3:1988', 'l3', 'latin3' | \n
'iso-8859-4' | \n'csisolatin4', 'iso-ir-110', 'iso8859-4', 'iso88594', 'iso_8859-4', 'iso_8859-4:1988', 'l4', 'latin4' | \n
'iso-8859-5' | \n'csisolatincyrillic', 'cyrillic', 'iso-ir-144', 'iso8859-5', 'iso88595', 'iso_8859-5', 'iso_8859-5:1988' | \n
'iso-8859-6' | \n'arabic', 'asmo-708', 'csiso88596e', 'csiso88596i', 'csisolatinarabic', 'ecma-114', 'iso-8859-6-e', 'iso-8859-6-i', 'iso-ir-127', 'iso8859-6', 'iso88596', 'iso_8859-6', 'iso_8859-6:1987' | \n
'iso-8859-7' | \n'csisolatingreek', 'ecma-118', 'elot_928', 'greek', 'greek8', 'iso-ir-126', 'iso8859-7', 'iso88597', 'iso_8859-7', 'iso_8859-7:1987', 'sun_eu_greek' | \n
'iso-8859-8' | \n'csiso88598e', 'csisolatinhebrew', 'hebrew', 'iso-8859-8-e', 'iso-ir-138', 'iso8859-8', 'iso88598', 'iso_8859-8', 'iso_8859-8:1988', 'visual' | \n
'iso-8859-8-i' | \n'csiso88598i', 'logical' | \n
'iso-8859-10' | \n'csisolatin6', 'iso-ir-157', 'iso8859-10', 'iso885910', 'l6', 'latin6' | \n
'iso-8859-13' | \n'iso8859-13', 'iso885913' | \n
'iso-8859-14' | \n'iso8859-14', 'iso885914' | \n
'iso-8859-15' | \n'csisolatin9', 'iso8859-15', 'iso885915', 'iso_8859-15', 'l9' | \n
'koi8-r' | \n'cskoi8r', 'koi', 'koi8', 'koi8_r' | \n
'koi8-u' | \n'koi8-ru' | \n
'macintosh' | \n'csmacintosh', 'mac', 'x-mac-roman' | \n
'windows-874' | \n'dos-874', 'iso-8859-11', 'iso8859-11', 'iso885911', 'tis-620' | \n
'windows-1250' | \n'cp1250', 'x-cp1250' | \n
'windows-1251' | \n'cp1251', 'x-cp1251' | \n
'windows-1252' | \n'ansi_x3.4-1968', 'ascii', 'cp1252', 'cp819', 'csisolatin1', 'ibm819', 'iso-8859-1', 'iso-ir-100', 'iso8859-1', 'iso88591', 'iso_8859-1', 'iso_8859-1:1987', 'l1', 'latin1', 'us-ascii', 'x-cp1252' | \n
'windows-1253' | \n'cp1253', 'x-cp1253' | \n
'windows-1254' | \n'cp1254', 'csisolatin5', 'iso-8859-9', 'iso-ir-148', 'iso8859-9', 'iso88599', 'iso_8859-9', 'iso_8859-9:1989', 'l5', 'latin5', 'x-cp1254' | \n
'windows-1255' | \n'cp1255', 'x-cp1255' | \n
'windows-1256' | \n'cp1256', 'x-cp1256' | \n
'windows-1257' | \n'cp1257', 'x-cp1257' | \n
'windows-1258' | \n'cp1258', 'x-cp1258' | \n
'x-mac-cyrillic' | \n'x-mac-ukrainian' | \n
'gbk' | \n'chinese', 'csgb2312', 'csiso58gb231280', 'gb2312', 'gb_2312', 'gb_2312-80', 'iso-ir-58', 'x-gbk' | \n
'gb18030' | \n\n |
'big5' | \n'big5-hkscs', 'cn-big5', 'csbig5', 'x-x-big5' | \n
'euc-jp' | \n'cseucpkdfmtjapanese', 'x-euc-jp' | \n
'iso-2022-jp' | \n'csiso2022jp' | \n
'shift_jis' | \n'csshiftjis', 'ms932', 'ms_kanji', 'shift-jis', 'sjis', 'windows-31j', 'x-sjis' | \n
'euc-kr' | \n'cseuckr', 'csksc56011987', 'iso-ir-149', 'korean', 'ks_c_5601-1987', 'ks_c_5601-1989', 'ksc5601', 'ksc_5601', 'windows-949' | \n
The 'iso-8859-16' encoding listed in the WHATWG Encoding Standard\nis not supported.
Decodes the input and returns a string. If options.stream is true, any\nincomplete byte sequences occurring at the end of the input are buffered\ninternally and emitted after the next call to textDecoder.decode().
If textDecoder.fatal is true, decoding errors that occur will result in a\nTypeError being thrown.
The encoding supported by the TextDecoder instance.
The value will be true if decoding errors result in a TypeError being\nthrown.
The value will be true if the decoding result will include the byte order\nmark.
Creates an new TextDecoder instance. The encoding may specify one of the\nsupported encodings or an alias.
An implementation of the WHATWG Encoding Standard TextEncoder API. All\ninstances of TextEncoder only support UTF-8 encoding.
const encoder = new TextEncoder();\nconst uint8array = encoder.encode('this is some data');\nUTF-8 encodes the input string and returns a Uint8Array containing the\nencoded bytes.
The encoding supported by the TextEncoder instance. Always set to 'utf-8'.
util.types provides a number of type checks for different kinds of built-in\nobjects. Unlike instanceof or Object.prototype.toString.call(value),\nthese checks do not inspect properties of the object that are accessible from\nJavaScript (like their prototype), and usually have the overhead of\ncalling into C++.
The result generally does not make any guarantees about what kinds of\nproperties or behavior a value exposes in JavaScript. They are primarily\nuseful for addon developers who prefer to do type checking in JavaScript.
", "methods": [ { "textRaw": "util.types.isAnyArrayBuffer(value)", "type": "method", "name": "isAnyArrayBuffer", "meta": { "added": [ "v10.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" } ] } ], "desc": "Returns true if the value is a built-in ArrayBuffer or\nSharedArrayBuffer instance.
See also util.types.isArrayBuffer() and\nutil.types.isSharedArrayBuffer().
util.types.isAnyArrayBuffer(new ArrayBuffer()); // Returns true\nutil.types.isAnyArrayBuffer(new SharedArrayBuffer()); // Returns true\nReturns true if the value is an arguments object.
function foo() {\n util.types.isArgumentsObject(arguments); // Returns true\n}\nReturns true if the value is a built-in ArrayBuffer instance.\nThis does not include SharedArrayBuffer instances. Usually, it is\ndesirable to test for both; See util.types.isAnyArrayBuffer() for that.
util.types.isArrayBuffer(new ArrayBuffer()); // Returns true\nutil.types.isArrayBuffer(new SharedArrayBuffer()); // Returns false\nReturns true if the value is an async function.\nNote that this only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
util.types.isAsyncFunction(function foo() {}); // Returns false\nutil.types.isAsyncFunction(async function foo() {}); // Returns true\nReturns true if the value is a BigInt64Array instance.
util.types.isBigInt64Array(new BigInt64Array()); // Returns true\nutil.types.isBigInt64Array(new BigUint64Array()); // Returns false\nReturns true if the value is a BigUint64Array instance.
util.types.isBigUint64Array(new BigInt64Array()); // Returns false\nutil.types.isBigUint64Array(new BigUint64Array()); // Returns true\nReturns true if the value is a boolean object, e.g. created\nby new Boolean().
util.types.isBooleanObject(false); // Returns false\nutil.types.isBooleanObject(true); // Returns false\nutil.types.isBooleanObject(new Boolean(false)); // Returns true\nutil.types.isBooleanObject(new Boolean(true)); // Returns true\nutil.types.isBooleanObject(Boolean(false)); // Returns false\nutil.types.isBooleanObject(Boolean(true)); // Returns false\nReturns true if the value is any boxed primitive object, e.g. created\nby new Boolean(), new String() or Object(Symbol()).
For example:
\nutil.types.isBoxedPrimitive(false); // Returns false\nutil.types.isBoxedPrimitive(new Boolean(false)); // Returns true\nutil.types.isBoxedPrimitive(Symbol('foo')); // Returns false\nutil.types.isBoxedPrimitive(Object(Symbol('foo'))); // Returns true\nutil.types.isBoxedPrimitive(Object(BigInt(5))); // Returns true\nReturns true if the value is a built-in DataView instance.
const ab = new ArrayBuffer(20);\nutil.types.isDataView(new DataView(ab)); // Returns true\nutil.types.isDataView(new Float64Array()); // Returns false\nSee also ArrayBuffer.isView().
Returns true if the value is a built-in Date instance.
util.types.isDate(new Date()); // Returns true\nReturns true if the value is a native External value.
Returns true if the value is a built-in Float32Array instance.
util.types.isFloat32Array(new ArrayBuffer()); // Returns false\nutil.types.isFloat32Array(new Float32Array()); // Returns true\nutil.types.isFloat32Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Float64Array instance.
util.types.isFloat64Array(new ArrayBuffer()); // Returns false\nutil.types.isFloat64Array(new Uint8Array()); // Returns false\nutil.types.isFloat64Array(new Float64Array()); // Returns true\nReturns true if the value is a generator function.\nNote that this only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
util.types.isGeneratorFunction(function foo() {}); // Returns false\nutil.types.isGeneratorFunction(function* foo() {}); // Returns true\nReturns true if the value is a generator object as returned from a\nbuilt-in generator function.\nNote that this only reports back what the JavaScript engine is seeing;\nin particular, the return value may not match the original source code if\na transpilation tool was used.
function* foo() {}\nconst generator = foo();\nutil.types.isGeneratorObject(generator); // Returns true\nReturns true if the value is a built-in Int8Array instance.
util.types.isInt8Array(new ArrayBuffer()); // Returns false\nutil.types.isInt8Array(new Int8Array()); // Returns true\nutil.types.isInt8Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Int16Array instance.
util.types.isInt16Array(new ArrayBuffer()); // Returns false\nutil.types.isInt16Array(new Int16Array()); // Returns true\nutil.types.isInt16Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Int32Array instance.
util.types.isInt32Array(new ArrayBuffer()); // Returns false\nutil.types.isInt32Array(new Int32Array()); // Returns true\nutil.types.isInt32Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Map instance.
util.types.isMap(new Map()); // Returns true\nReturns true if the value is an iterator returned for a built-in\nMap instance.
const map = new Map();\nutil.types.isMapIterator(map.keys()); // Returns true\nutil.types.isMapIterator(map.values()); // Returns true\nutil.types.isMapIterator(map.entries()); // Returns true\nutil.types.isMapIterator(map[Symbol.iterator]()); // Returns true\nReturns true if the value is an instance of a Module Namespace Object.
import * as ns from './a.js';\n\nutil.types.isModuleNamespaceObject(ns); // Returns true\nReturns true if the value is an instance of a built-in Error type.
util.types.isNativeError(new Error()); // Returns true\nutil.types.isNativeError(new TypeError()); // Returns true\nutil.types.isNativeError(new RangeError()); // Returns true\nReturns true if the value is a number object, e.g. created\nby new Number().
util.types.isNumberObject(0); // Returns false\nutil.types.isNumberObject(new Number(0)); // Returns true\nReturns true if the value is a built-in Promise.
util.types.isPromise(Promise.resolve(42)); // Returns true\nReturns true if the value is a Proxy instance.
const target = {};\nconst proxy = new Proxy(target, {});\nutil.types.isProxy(target); // Returns false\nutil.types.isProxy(proxy); // Returns true\nReturns true if the value is a regular expression object.
util.types.isRegExp(/abc/); // Returns true\nutil.types.isRegExp(new RegExp('abc')); // Returns true\nReturns true if the value is a built-in Set instance.
util.types.isSet(new Set()); // Returns true\nReturns true if the value is an iterator returned for a built-in\nSet instance.
const set = new Set();\nutil.types.isSetIterator(set.keys()); // Returns true\nutil.types.isSetIterator(set.values()); // Returns true\nutil.types.isSetIterator(set.entries()); // Returns true\nutil.types.isSetIterator(set[Symbol.iterator]()); // Returns true\nReturns true if the value is a built-in SharedArrayBuffer instance.\nThis does not include ArrayBuffer instances. Usually, it is\ndesirable to test for both; See util.types.isAnyArrayBuffer() for that.
util.types.isSharedArrayBuffer(new ArrayBuffer()); // Returns false\nutil.types.isSharedArrayBuffer(new SharedArrayBuffer()); // Returns true\nReturns true if the value is a string object, e.g. created\nby new String().
util.types.isStringObject('foo'); // Returns false\nutil.types.isStringObject(new String('foo')); // Returns true\nReturns true if the value is a symbol object, created\nby calling Object() on a Symbol primitive.
const symbol = Symbol('foo');\nutil.types.isSymbolObject(symbol); // Returns false\nutil.types.isSymbolObject(Object(symbol)); // Returns true\nReturns true if the value is a built-in TypedArray instance.
util.types.isTypedArray(new ArrayBuffer()); // Returns false\nutil.types.isTypedArray(new Uint8Array()); // Returns true\nutil.types.isTypedArray(new Float64Array()); // Returns true\nSee also ArrayBuffer.isView().
Returns true if the value is a built-in Uint8Array instance.
util.types.isUint8Array(new ArrayBuffer()); // Returns false\nutil.types.isUint8Array(new Uint8Array()); // Returns true\nutil.types.isUint8Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Uint8ClampedArray instance.
util.types.isUint8ClampedArray(new ArrayBuffer()); // Returns false\nutil.types.isUint8ClampedArray(new Uint8ClampedArray()); // Returns true\nutil.types.isUint8ClampedArray(new Float64Array()); // Returns false\nReturns true if the value is a built-in Uint16Array instance.
util.types.isUint16Array(new ArrayBuffer()); // Returns false\nutil.types.isUint16Array(new Uint16Array()); // Returns true\nutil.types.isUint16Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in Uint32Array instance.
util.types.isUint32Array(new ArrayBuffer()); // Returns false\nutil.types.isUint32Array(new Uint32Array()); // Returns true\nutil.types.isUint32Array(new Float64Array()); // Returns false\nReturns true if the value is a built-in WeakMap instance.
util.types.isWeakMap(new WeakMap()); // Returns true\nReturns true if the value is a built-in WeakSet instance.
util.types.isWeakSet(new WeakSet()); // Returns true\nReturns true if the value is a built-in WebAssembly.Module instance.
const module = new WebAssembly.Module(wasmBuffer);\nutil.types.isWebAssemblyCompiledModule(module); // Returns true\nThe following APIs are deprecated and should no longer be used. Existing\napplications and modules should be updated to find alternative approaches.
", "methods": [ { "textRaw": "util._extend(target, source)", "type": "method", "name": "_extend", "meta": { "added": [ "v0.7.5" ], "deprecated": [ "v6.0.0" ], "changes": [] }, "stability": 0, "stabilityText": "Deprecated: Use [`Object.assign()`] instead.", "signatures": [ { "params": [ { "textRaw": "`target` {Object}", "name": "target", "type": "Object" }, { "textRaw": "`source` {Object}", "name": "source", "type": "Object" } ] } ], "desc": "The util._extend() method was never intended to be used outside of internal\nNode.js modules. The community found and used it anyway.
It is deprecated and should not be used in new code. JavaScript comes with very\nsimilar built-in functionality through Object.assign().
Deprecated predecessor of console.error.
Deprecated predecessor of console.error.
Alias for Array.isArray().
Returns true if the given object is an Array. Otherwise, returns false.
const util = require('util');\n\nutil.isArray([]);\n// Returns: true\nutil.isArray(new Array());\n// Returns: true\nutil.isArray({});\n// Returns: false\nReturns true if the given object is a Boolean. Otherwise, returns false.
const util = require('util');\n\nutil.isBoolean(1);\n// Returns: false\nutil.isBoolean(0);\n// Returns: false\nutil.isBoolean(false);\n// Returns: true\nReturns true if the given object is a Buffer. Otherwise, returns false.
const util = require('util');\n\nutil.isBuffer({ length: 0 });\n// Returns: false\nutil.isBuffer([]);\n// Returns: false\nutil.isBuffer(Buffer.from('hello world'));\n// Returns: true\nReturns true if the given object is a Date. Otherwise, returns false.
const util = require('util');\n\nutil.isDate(new Date());\n// Returns: true\nutil.isDate(Date());\n// false (without 'new' returns a String)\nutil.isDate({});\n// Returns: false\nReturns true if the given object is an Error. Otherwise, returns\nfalse.
const util = require('util');\n\nutil.isError(new Error());\n// Returns: true\nutil.isError(new TypeError());\n// Returns: true\nutil.isError({ name: 'Error', message: 'an error occurred' });\n// Returns: false\nNote that this method relies on Object.prototype.toString() behavior. It is\npossible to obtain an incorrect result when the object argument manipulates\n@@toStringTag.
const util = require('util');\nconst obj = { name: 'Error', message: 'an error occurred' };\n\nutil.isError(obj);\n// Returns: false\nobj[Symbol.toStringTag] = 'Error';\nutil.isError(obj);\n// Returns: true\nReturns true if the given object is a Function. Otherwise, returns\nfalse.
const util = require('util');\n\nfunction Foo() {}\nconst Bar = () => {};\n\nutil.isFunction({});\n// Returns: false\nutil.isFunction(Foo);\n// Returns: true\nutil.isFunction(Bar);\n// Returns: true\nReturns true if the given object is strictly null. Otherwise, returns\nfalse.
const util = require('util');\n\nutil.isNull(0);\n// Returns: false\nutil.isNull(undefined);\n// Returns: false\nutil.isNull(null);\n// Returns: true\nReturns true if the given object is null or undefined. Otherwise,\nreturns false.
const util = require('util');\n\nutil.isNullOrUndefined(0);\n// Returns: false\nutil.isNullOrUndefined(undefined);\n// Returns: true\nutil.isNullOrUndefined(null);\n// Returns: true\nReturns true if the given object is a Number. Otherwise, returns false.
const util = require('util');\n\nutil.isNumber(false);\n// Returns: false\nutil.isNumber(Infinity);\n// Returns: true\nutil.isNumber(0);\n// Returns: true\nutil.isNumber(NaN);\n// Returns: true\nReturns true if the given object is strictly an Object and not a\nFunction (even though functions are objects in JavaScript).\nOtherwise, returns false.
const util = require('util');\n\nutil.isObject(5);\n// Returns: false\nutil.isObject(null);\n// Returns: false\nutil.isObject({});\n// Returns: true\nutil.isObject(() => {});\n// Returns: false\nReturns true if the given object is a primitive type. Otherwise, returns\nfalse.
const util = require('util');\n\nutil.isPrimitive(5);\n// Returns: true\nutil.isPrimitive('foo');\n// Returns: true\nutil.isPrimitive(false);\n// Returns: true\nutil.isPrimitive(null);\n// Returns: true\nutil.isPrimitive(undefined);\n// Returns: true\nutil.isPrimitive({});\n// Returns: false\nutil.isPrimitive(() => {});\n// Returns: false\nutil.isPrimitive(/^$/);\n// Returns: false\nutil.isPrimitive(new Date());\n// Returns: false\nReturns true if the given object is a RegExp. Otherwise, returns false.
const util = require('util');\n\nutil.isRegExp(/some regexp/);\n// Returns: true\nutil.isRegExp(new RegExp('another regexp'));\n// Returns: true\nutil.isRegExp({});\n// Returns: false\nReturns true if the given object is a string. Otherwise, returns false.
const util = require('util');\n\nutil.isString('');\n// Returns: true\nutil.isString('foo');\n// Returns: true\nutil.isString(String('foo'));\n// Returns: true\nutil.isString(5);\n// Returns: false\nReturns true if the given object is a Symbol. Otherwise, returns false.
const util = require('util');\n\nutil.isSymbol(5);\n// Returns: false\nutil.isSymbol('foo');\n// Returns: false\nutil.isSymbol(Symbol('foo'));\n// Returns: true\nReturns true if the given object is undefined. Otherwise, returns false.
const util = require('util');\n\nconst foo = undefined;\nutil.isUndefined(5);\n// Returns: false\nutil.isUndefined(foo);\n// Returns: true\nutil.isUndefined(null);\n// Returns: false\nThe util.log() method prints the given string to stdout with an included\ntimestamp.
const util = require('util');\n\nutil.log('Timestamped message.');\nDeprecated predecessor of console.log.
Deprecated predecessor of console.log.
The v8 module exposes APIs that are specific to the version of V8\nbuilt into the Node.js binary. It can be accessed using:
const v8 = require('v8');\nThe APIs and implementation are subject to change at any time.
", "methods": [ { "textRaw": "v8.cachedDataVersionTag()", "type": "method", "name": "cachedDataVersionTag", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer}", "name": "return", "type": "integer" }, "params": [] } ], "desc": "Returns an integer representing a \"version tag\" derived from the V8 version,\ncommand line flags and detected CPU features. This is useful for determining\nwhether a vm.Script cachedData buffer is compatible with this instance\nof V8.
Returns statistics about the V8 heap spaces, i.e. the segments which make up\nthe V8 heap. Neither the ordering of heap spaces, nor the availability of a\nheap space can be guaranteed as the statistics are provided via the V8\nGetHeapSpaceStatistics function and may change from one V8 version to the\nnext.
The value returned is an array of objects containing the following properties:
\nspace_name <string>space_size <number>space_used_size <number>space_available_size <number>physical_space_size <number>[\n {\n \"space_name\": \"new_space\",\n \"space_size\": 2063872,\n \"space_used_size\": 951112,\n \"space_available_size\": 80824,\n \"physical_space_size\": 2063872\n },\n {\n \"space_name\": \"old_space\",\n \"space_size\": 3090560,\n \"space_used_size\": 2493792,\n \"space_available_size\": 0,\n \"physical_space_size\": 3090560\n },\n {\n \"space_name\": \"code_space\",\n \"space_size\": 1260160,\n \"space_used_size\": 644256,\n \"space_available_size\": 960,\n \"physical_space_size\": 1260160\n },\n {\n \"space_name\": \"map_space\",\n \"space_size\": 1094160,\n \"space_used_size\": 201608,\n \"space_available_size\": 0,\n \"physical_space_size\": 1094160\n },\n {\n \"space_name\": \"large_object_space\",\n \"space_size\": 0,\n \"space_used_size\": 0,\n \"space_available_size\": 1490980608,\n \"physical_space_size\": 0\n }\n]\nReturns an object with the following properties:
\ntotal_heap_size <number>total_heap_size_executable <number>total_physical_size <number>total_available_size <number>used_heap_size <number>heap_size_limit <number>malloced_memory <number>peak_malloced_memory <number>does_zap_garbage <number>does_zap_garbage is a 0/1 boolean, which signifies whether the\n--zap_code_space option is enabled or not. This makes V8 overwrite heap\ngarbage with a bit pattern. The RSS footprint (resident memory set) gets bigger\nbecause it continuously touches all heap pages and that makes them less likely\nto get swapped out by the operating system.
{\n total_heap_size: 7326976,\n total_heap_size_executable: 4194304,\n total_physical_size: 7326976,\n total_available_size: 1152656,\n used_heap_size: 3476208,\n heap_size_limit: 1535115264,\n malloced_memory: 16384,\n peak_malloced_memory: 1127496,\n does_zap_garbage: 0\n}\nThe v8.setFlagsFromString() method can be used to programmatically set\nV8 command line flags. This method should be used with care. Changing settings\nafter the VM has started may result in unpredictable behavior, including\ncrashes and data loss; or it may simply do nothing.
The V8 options available for a version of Node.js may be determined by running\nnode --v8-options. An unofficial, community-maintained list of options\nand their effects is available here.
Usage:
\n// Print GC events to stdout for one minute.\nconst v8 = require('v8');\nv8.setFlagsFromString('--trace_gc');\nsetTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);\nThe serialization API provides means of serializing JavaScript values in a way\nthat is compatible with the HTML structured clone algorithm.\nThe format is backward-compatible (i.e. safe to store to disk).
\nThis API is under development, and changes (including incompatible\nchanges to the API or wire format) may occur until this warning is removed.
", "methods": [ { "textRaw": "v8.serialize(value)", "type": "method", "name": "serialize", "meta": { "added": [ "v8.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Buffer}", "name": "return", "type": "Buffer" }, "params": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" } ] } ], "desc": "Uses a DefaultSerializer to serialize value into a buffer.
Uses a DefaultDeserializer with default options to read a JS value\nfrom a buffer.
Writes out a header, which includes the serialization format version.
" }, { "textRaw": "serializer.writeValue(value)", "type": "method", "name": "writeValue", "signatures": [ { "params": [ { "textRaw": "`value` {any}", "name": "value", "type": "any" } ] } ], "desc": "Serializes a JavaScript value and adds the serialized representation to the\ninternal buffer.
\nThis throws an error if value cannot be serialized.
Returns the stored internal buffer. This serializer should not be used once\nthe buffer is released. Calling this method results in undefined behavior\nif a previous write has failed.
" }, { "textRaw": "serializer.transferArrayBuffer(id, arrayBuffer)", "type": "method", "name": "transferArrayBuffer", "signatures": [ { "params": [ { "textRaw": "`id` {integer} A 32-bit unsigned integer.", "name": "id", "type": "integer", "desc": "A 32-bit unsigned integer." }, { "textRaw": "`arrayBuffer` {ArrayBuffer} An `ArrayBuffer` instance.", "name": "arrayBuffer", "type": "ArrayBuffer", "desc": "An `ArrayBuffer` instance." } ] } ], "desc": "Marks an ArrayBuffer as havings its contents transferred out of band.\nPass the corresponding ArrayBuffer in the deserializing context to\ndeserializer.transferArrayBuffer().
Write a raw 32-bit unsigned integer.\nFor use inside of a custom serializer._writeHostObject().
Write a raw 64-bit unsigned integer, split into high and low 32-bit parts.\nFor use inside of a custom serializer._writeHostObject().
Write a JS number value.\nFor use inside of a custom serializer._writeHostObject().
Write raw bytes into the serializer’s internal buffer. The deserializer\nwill require a way to compute the length of the buffer.\nFor use inside of a custom serializer._writeHostObject().
This method is called to write some kind of host object, i.e. an object created\nby native C++ bindings. If it is not possible to serialize object, a suitable\nexception should be thrown.
This method is not present on the Serializer class itself but can be provided\nby subclasses.
This method is called to generate error objects that will be thrown when an\nobject can not be cloned.
\nThis method defaults to the Error constructor and can be overridden on\nsubclasses.
This method is called when the serializer is going to serialize a\nSharedArrayBuffer object. It must return an unsigned 32-bit integer ID for\nthe object, using the same ID if this SharedArrayBuffer has already been\nserialized. When deserializing, this ID will be passed to\ndeserializer.transferArrayBuffer().
If the object cannot be serialized, an exception should be thrown.
\nThis method is not present on the Serializer class itself but can be provided\nby subclasses.
Indicate whether to treat TypedArray and DataView objects as\nhost objects, i.e. pass them to serializer._writeHostObject().
Creates a new Serializer object.
Reads and validates a header (including the format version).\nMay, for example, reject an invalid or unsupported wire format. In that case,\nan Error is thrown.
Deserializes a JavaScript value from the buffer and returns it.
" }, { "textRaw": "deserializer.transferArrayBuffer(id, arrayBuffer)", "type": "method", "name": "transferArrayBuffer", "signatures": [ { "params": [ { "textRaw": "`id` {integer} A 32-bit unsigned integer.", "name": "id", "type": "integer", "desc": "A 32-bit unsigned integer." }, { "textRaw": "`arrayBuffer` {ArrayBuffer|SharedArrayBuffer} An `ArrayBuffer` instance.", "name": "arrayBuffer", "type": "ArrayBuffer|SharedArrayBuffer", "desc": "An `ArrayBuffer` instance." } ] } ], "desc": "Marks an ArrayBuffer as havings its contents transferred out of band.\nPass the corresponding ArrayBuffer in the serializing context to\nserializer.transferArrayBuffer() (or return the id from\nserializer._getSharedArrayBufferId() in the case of SharedArrayBuffers).
Reads the underlying wire format version. Likely mostly to be useful to\nlegacy code reading old wire format versions. May not be called before\n.readHeader().
Read a raw 32-bit unsigned integer and return it.\nFor use inside of a custom deserializer._readHostObject().
Read a raw 64-bit unsigned integer and return it as an array [hi, lo]\nwith two 32-bit unsigned integer entries.\nFor use inside of a custom deserializer._readHostObject().
Read a JS number value.\nFor use inside of a custom deserializer._readHostObject().
Read raw bytes from the deserializer’s internal buffer. The length parameter\nmust correspond to the length of the buffer that was passed to\nserializer.writeRawBytes().\nFor use inside of a custom deserializer._readHostObject().
This method is called to read some kind of host object, i.e. an object that is\ncreated by native C++ bindings. If it is not possible to deserialize the data,\na suitable exception should be thrown.
\nThis method is not present on the Deserializer class itself but can be\nprovided by subclasses.
Creates a new Deserializer object.
A subclass of Serializer that serializes TypedArray\n(in particular Buffer) and DataView objects as host objects, and only\nstores the part of their underlying ArrayBuffers that they are referring to.
A subclass of Deserializer corresponding to the format written by\nDefaultSerializer.
The vm module provides APIs for compiling and running code within V8 Virtual\nMachine contexts. The vm module is not a security mechanism. Do\nnot use it to run untrusted code. The term \"sandbox\" is used throughout these\ndocs simply to refer to a separate context, and does not confer any security\nguarantees.
JavaScript code can be compiled and run immediately or\ncompiled, saved, and run later.
\nA common use case is to run the code in a sandboxed environment.\nThe sandboxed code uses a different V8 Context, meaning that\nit has a different global object than the rest of the code.
\nOne can provide the context by \"contextifying\" a sandbox\nobject. The sandboxed code treats any property in the sandbox like a\nglobal variable. Any changes to global variables caused by the sandboxed\ncode are reflected in the sandbox object.
\nconst vm = require('vm');\n\nconst x = 1;\n\nconst sandbox = { x: 2 };\nvm.createContext(sandbox); // Contextify the sandbox.\n\nconst code = 'x += 40; var y = 17;';\n// x and y are global variables in the sandboxed environment.\n// Initially, x has the value 2 because that is the value of sandbox.x.\nvm.runInContext(code, sandbox);\n\nconsole.log(sandbox.x); // 42\nconsole.log(sandbox.y); // 17\n\nconsole.log(x); // 1; y is not defined.\nThis feature is only available with the --experimental-vm-modules command\nflag enabled.
The vm.SourceTextModule class provides a low-level interface for using\nECMAScript modules in VM contexts. It is the counterpart of the vm.Script\nclass that closely mirrors Source Text Module Records as defined in the\nECMAScript specification.
Unlike vm.Script however, every vm.SourceTextModule object is bound to a\ncontext from its creation. Operations on vm.SourceTextModule objects are\nintrinsically asynchronous, in contrast with the synchronous nature of\nvm.Script objects. With the help of async functions, however, manipulating\nvm.SourceTextModule objects is fairly straightforward.
Using a vm.SourceTextModule object requires four distinct steps:\ncreation/parsing, linking, instantiation, and evaluation. These four steps are\nillustrated in the following example.
This implementation lies at a lower level than the ECMAScript Module\nloader. There is also currently no way to interact with the Loader, though\nsupport is planned.
\nconst vm = require('vm');\n\nconst contextifiedSandbox = vm.createContext({ secret: 42 });\n\n(async () => {\n // Step 1\n //\n // Create a Module by constructing a new `vm.SourceTextModule` object. This\n // parses the provided source text, throwing a `SyntaxError` if anything goes\n // wrong. By default, a Module is created in the top context. But here, we\n // specify `contextifiedSandbox` as the context this Module belongs to.\n //\n // Here, we attempt to obtain the default export from the module \"foo\", and\n // put it into local binding \"secret\".\n\n const bar = new vm.SourceTextModule(`\n import s from 'foo';\n s;\n `, { context: contextifiedSandbox });\n\n // Step 2\n //\n // \"Link\" the imported dependencies of this Module to it.\n //\n // The provided linking callback (the \"linker\") accepts two arguments: the\n // parent module (`bar` in this case) and the string that is the specifier of\n // the imported module. The callback is expected to return a Module that\n // corresponds to the provided specifier, with certain requirements documented\n // in `module.link()`.\n //\n // If linking has not started for the returned Module, the same linker\n // callback will be called on the returned Module.\n //\n // Even top-level Modules without dependencies must be explicitly linked. The\n // callback provided would never be called, however.\n //\n // The link() method returns a Promise that will be resolved when all the\n // Promises returned by the linker resolve.\n //\n // Note: This is a contrived example in that the linker function creates a new\n // \"foo\" module every time it is called. In a full-fledged module system, a\n // cache would probably be used to avoid duplicated modules.\n\n async function linker(specifier, referencingModule) {\n if (specifier === 'foo') {\n return new vm.SourceTextModule(`\n // The \"secret\" variable refers to the global variable we added to\n // \"contextifiedSandbox\" when creating the context.\n export default secret;\n `, { context: referencingModule.context });\n\n // Using `contextifiedSandbox` instead of `referencingModule.context`\n // here would work as well.\n }\n throw new Error(`Unable to resolve dependency: ${specifier}`);\n }\n await bar.link(linker);\n\n // Step 3\n //\n // Instantiate the top-level Module.\n //\n // Only the top-level Module needs to be explicitly instantiated; its\n // dependencies will be recursively instantiated by instantiate().\n\n bar.instantiate();\n\n // Step 4\n //\n // Evaluate the Module. The evaluate() method returns a Promise with a single\n // property \"result\" that contains the result of the very last statement\n // executed in the Module. In the case of `bar`, it is `s;`, which refers to\n // the default export of the `foo` module, the `secret` we set in the\n // beginning to 42.\n\n const { result } = await bar.evaluate();\n\n console.log(result);\n // Prints 42.\n})();\nThe specifiers of all dependencies of this module. The returned array is frozen\nto disallow any changes to it.
\nCorresponds to the [[RequestedModules]] field of\nSource Text Module Records in the ECMAScript specification.
If the module.status is 'errored', this property contains the exception\nthrown by the module during evaluation. If the status is anything else,\naccessing this property will result in a thrown exception.
The value undefined cannot be used for cases where there is not a thrown\nexception due to possible ambiguity with throw undefined;.
Corresponds to the [[EvaluationError]] field of Source Text Module Records\nin the ECMAScript specification.
The current linking status of module. It will be one of the following values:
'unlinked': module.link() has not yet been called.'linking': module.link() has been called, but not all Promises returned by\nthe linker function have been resolved yet.'linked': module.link() has been called, and all its dependencies have\nbeen successfully linked.'errored': module.link() has been called, but at least one of its\ndependencies failed to link, either because the callback returned a Promise\nthat is rejected, or because the Module the callback returned is invalid.The namespace object of the module. This is only available after instantiation\n(module.instantiate()) has completed.
Corresponds to the GetModuleNamespace abstract operation in the ECMAScript\nspecification.
" }, { "textRaw": "`status` {string}", "type": "string", "name": "status", "desc": "The current status of the module. Will be one of:
\n'uninstantiated': The module is not instantiated. It may because of any of\nthe following reasons:
module.instantiate() has been called on this module, but it failed for\nsome reason.This status does not convey any information regarding if module.link() has\nbeen called. See module.linkingStatus for that.
'instantiating': The module is currently being instantiated through a\nmodule.instantiate() call on itself or a parent module.
'instantiated': The module has been instantiated successfully, but\nmodule.evaluate() has not yet been called.
'evaluating': The module is being evaluated through a module.evaluate() on\nitself or a parent module.
'evaluated': The module has been successfully evaluated.
'errored': The module has been evaluated, but an exception was thrown.
Other than 'errored', this status string corresponds to the specification's\nSource Text Module Record's [[Status]] field. 'errored' corresponds to\n'evaluated' in the specification, but with [[EvaluationError]] set to a\nvalue that is not undefined.
The URL of the current module, as set in the constructor.
" } ], "methods": [ { "textRaw": "module.evaluate([options])", "type": "method", "name": "evaluate", "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`options` {Object}", "name": "options", "type": "Object", "options": [ { "textRaw": "`timeout` {integer} Specifies the number of milliseconds to evaluate before terminating execution. If execution is interrupted, an [`Error`][] will be thrown. This value must be a strictly positive integer.", "name": "timeout", "type": "integer", "desc": "Specifies the number of milliseconds to evaluate before terminating execution. If execution is interrupted, an [`Error`][] will be thrown. This value must be a strictly positive integer." }, { "textRaw": "`breakOnSigint` {boolean} If `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is interrupted, an [`Error`][] will be thrown.", "name": "breakOnSigint", "type": "boolean", "desc": "If `true`, the execution will be terminated when `SIGINT` (Ctrl+C) is received. Existing handlers for the event that have been attached via `process.on('SIGINT')` will be disabled during script execution, but will continue to work after that. If execution is interrupted, an [`Error`][] will be thrown." } ], "optional": true } ] } ], "desc": "Evaluate the module.
\nThis must be called after the module has been instantiated; otherwise it will\nthrow an error. It could be called also when the module has already been\nevaluated, in which case it will do one of the following two things:
\nundefined if the initial evaluation ended in success (module.status\nis 'evaluated')module.status is 'errored')This method cannot be called while the module is being evaluated\n(module.status is 'evaluating') to prevent infinite recursion.
Corresponds to the Evaluate() concrete method field of Source Text Module\nRecords in the ECMAScript specification.
" }, { "textRaw": "module.instantiate()", "type": "method", "name": "instantiate", "signatures": [ { "params": [] } ], "desc": "Instantiate the module. This must be called after linking has completed\n(linkingStatus is 'linked'); otherwise it will throw an error. It may also\nthrow an exception if one of the dependencies does not provide an export the\nparent module requires.
However, if this function succeeded, further calls to this function after the\ninitial instantiation will be no-ops, to be consistent with the ECMAScript\nspecification.
\nUnlike other methods operating on Module, this function completes\nsynchronously and returns nothing.
Corresponds to the Instantiate() concrete method field of Source Text\nModule Records in the ECMAScript specification.
" }, { "textRaw": "module.link(linker)", "type": "method", "name": "link", "signatures": [ { "return": { "textRaw": "Returns: {Promise}", "name": "return", "type": "Promise" }, "params": [ { "textRaw": "`linker` {Function}", "name": "linker", "type": "Function" } ] } ], "desc": "Link module dependencies. This method must be called before instantiation, and\ncan only be called once per module.
\nTwo parameters will be passed to the linker function:
specifier The specifier of the requested module:
import foo from 'foo';\n// ^^^^^ the module specifier\nreferencingModule The Module object link() is called on.The function is expected to return a Module object or a Promise that\neventually resolves to a Module object. The returned Module must satisfy the\nfollowing two invariants:
Module.linkingStatus must not be 'errored'.If the returned Module's linkingStatus is 'unlinked', this method will be\nrecursively called on the returned Module with the same provided linker\nfunction.
link() returns a Promise that will either get resolved when all linking\ninstances resolve to a valid Module, or rejected if the linker function either\nthrows an exception or returns an invalid Module.
The linker function roughly corresponds to the implementation-defined\nHostResolveImportedModule abstract operation in the ECMAScript\nspecification, with a few key differences:
\nThe actual HostResolveImportedModule implementation used during module\ninstantiation is one that returns the modules linked during linking. Since at\nthat point all modules would have been fully linked already, the\nHostResolveImportedModule implementation is fully synchronous per\nspecification.
" } ], "signatures": [ { "params": [ { "textRaw": "`code` {string} JavaScript Module code to parse", "name": "code", "type": "string", "desc": "JavaScript Module code to parse" }, { "textRaw": "`options`", "name": "options", "options": [ { "textRaw": "`url` {string} URL used in module resolution and stack traces. **Default:** `'vm:module(i)'` where `i` is a context-specific ascending index.", "name": "url", "type": "string", "default": "`'vm:module(i)'` where `i` is a context-specific ascending index", "desc": "URL used in module resolution and stack traces." }, { "textRaw": "`context` {Object} The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in.", "name": "context", "type": "Object", "desc": "The [contextified][] object as returned by the `vm.createContext()` method, to compile and evaluate this `Module` in." }, { "textRaw": "`lineOffset` {integer} Specifies the line number offset that is displayed in stack traces produced by this `Module`.", "name": "lineOffset", "type": "integer", "desc": "Specifies the line number offset that is displayed in stack traces produced by this `Module`." }, { "textRaw": "`columnOffset` {integer} Specifies the column number offset that is displayed in stack traces produced by this `Module`.", "name": "columnOffset", "type": "integer", "desc": "Specifies the column number offset that is displayed in stack traces produced by this `Module`." }, { "textRaw": "`initializeImportMeta` {Function} Called during evaluation of this `Module` to initialize the `import.meta`. This function has the signature `(meta, module)`, where `meta` is the `import.meta` object in the `Module`, and `module` is this `vm.SourceTextModule` object.", "name": "initializeImportMeta", "type": "Function", "desc": "Called during evaluation of this `Module` to initialize the `import.meta`. This function has the signature `(meta, module)`, where `meta` is the `import.meta` object in the `Module`, and `module` is this `vm.SourceTextModule` object." }, { "textRaw": "`importModuleDynamically` {Function} Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports.", "name": "importModuleDynamically", "type": "Function", "desc": "Called during evaluation of this module when `import()` is called. This function has the signature `(specifier, module)` where `specifier` is the specifier passed to `import()` and `module` is this `vm.SourceTextModule`. If this option is not specified, calls to `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][]. This method can return a [Module Namespace Object][], but returning a `vm.SourceTextModule` is recommended in order to take advantage of error tracking, and to avoid issues with namespaces that contain `then` function exports." } ], "optional": true } ], "desc": "Creates a new ES Module object.
Properties assigned to the import.meta object that are objects may\nallow the Module to access information outside the specified context, if the\nobject is created in the top level context. Use vm.runInContext() to create\nobjects in a specific context.
const vm = require('vm');\n\nconst contextifiedSandbox = vm.createContext({ secret: 42 });\n\n(async () => {\n const module = new vm.SourceTextModule(\n 'Object.getPrototypeOf(import.meta.prop).secret = secret;',\n {\n initializeImportMeta(meta) {\n // Note: this object is created in the top context. As such,\n // Object.getPrototypeOf(import.meta.prop) points to the\n // Object.prototype in the top context rather than that in\n // the sandbox.\n meta.prop = {};\n }\n });\n // Since module has no dependencies, the linker function will never be called.\n await module.link(() => {});\n module.instantiate();\n await module.evaluate();\n\n // Now, Object.prototype.secret will be equal to 42.\n //\n // To fix this problem, replace\n // meta.prop = {};\n // above with\n // meta.prop = vm.runInContext('{}', contextifiedSandbox);\n})();\nInstances of the vm.Script class contain precompiled scripts that can be\nexecuted in specific sandboxes (or \"contexts\").
Creates a code cache that can be used with the Script constructor's\ncachedData option. Returns a Buffer. This method may be called at any\ntime and any number of times.
const script = new vm.Script(`\nfunction add(a, b) {\n return a + b;\n}\n\nconst x = add(1, 2);\n`);\n\nconst cacheWithoutX = script.createCachedData();\n\nscript.runInThisContext();\n\nconst cacheWithX = script.createCachedData();\nRuns the compiled code contained by the vm.Script object within the given\ncontextifiedSandbox and returns the result. Running code does not have access\nto local scope.
The following example compiles code that increments a global variable, sets\nthe value of another global variable, then execute the code multiple times.\nThe globals are contained in the sandbox object.
const util = require('util');\nconst vm = require('vm');\n\nconst sandbox = {\n animal: 'cat',\n count: 2\n};\n\nconst script = new vm.Script('count += 1; name = \"kitty\";');\n\nconst context = vm.createContext(sandbox);\nfor (let i = 0; i < 10; ++i) {\n script.runInContext(context);\n}\n\nconsole.log(util.inspect(sandbox));\n\n// { animal: 'cat', count: 12, name: 'kitty' }\nUsing the timeout or breakOnSigint options will result in new event loops\nand corresponding threads being started, which have a non-zero performance\noverhead.
First contextifies the given sandbox, runs the compiled code contained by\nthe vm.Script object within the created sandbox, and returns the result.\nRunning code does not have access to local scope.
The following example compiles code that sets a global variable, then executes\nthe code multiple times in different contexts. The globals are set on and\ncontained within each individual sandbox.
const util = require('util');\nconst vm = require('vm');\n\nconst script = new vm.Script('globalVar = \"set\"');\n\nconst sandboxes = [{}, {}, {}];\nsandboxes.forEach((sandbox) => {\n script.runInNewContext(sandbox);\n});\n\nconsole.log(util.inspect(sandboxes));\n\n// [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]\nRuns the compiled code contained by the vm.Script within the context of the\ncurrent global object. Running code does not have access to local scope, but\ndoes have access to the current global object.
The following example compiles code that increments a global variable then\nexecutes that code multiple times:
const vm = require('vm');\n\nglobal.globalVar = 0;\n\nconst script = new vm.Script('globalVar += 1', { filename: 'myfile.vm' });\n\nfor (let i = 0; i < 1000; ++i) {\n script.runInThisContext();\n}\n\nconsole.log(globalVar);\n\n// 1000\nCreating a new vm.Script object compiles code but does not run it. The\ncompiled vm.Script can be run later multiple times. The code is not bound to\nany global object; rather, it is bound before each run, just for that run.
Compiles the given code into the provided context/sandbox (if no context is\nsupplied, the current context is used), and returns it wrapped inside a\nfunction with the given params.
If given a sandbox object, the vm.createContext() method will prepare\nthat sandbox so that it can be used in calls to\nvm.runInContext() or script.runInContext(). Inside such scripts,\nthe sandbox object will be the global object, retaining all of its existing\nproperties but also having the built-in objects and functions any standard\nglobal object has. Outside of scripts run by the vm module, global variables\nwill remain unchanged.
const util = require('util');\nconst vm = require('vm');\n\nglobal.globalVar = 3;\n\nconst sandbox = { globalVar: 1 };\nvm.createContext(sandbox);\n\nvm.runInContext('globalVar *= 2;', sandbox);\n\nconsole.log(util.inspect(sandbox)); // { globalVar: 2 }\n\nconsole.log(util.inspect(globalVar)); // 3\nIf sandbox is omitted (or passed explicitly as undefined), a new, empty\ncontextified sandbox object will be returned.
The vm.createContext() method is primarily useful for creating a single\nsandbox that can be used to run multiple scripts. For instance, if emulating a\nweb browser, the method can be used to create a single sandbox representing a\nwindow's global object, then run all <script> tags together within the context\nof that sandbox.
The provided name and origin of the context are made visible through the\nInspector API.
Returns true if the given sandbox object has been contextified using\nvm.createContext().
The vm.runInContext() method compiles code, runs it within the context of\nthe contextifiedSandbox, then returns the result. Running code does not have\naccess to the local scope. The contextifiedSandbox object must have been\npreviously contextified using the vm.createContext() method.
If options is a string, then it specifies the filename.
The following example compiles and executes different scripts using a single\ncontextified object:
\nconst util = require('util');\nconst vm = require('vm');\n\nconst sandbox = { globalVar: 1 };\nvm.createContext(sandbox);\n\nfor (let i = 0; i < 10; ++i) {\n vm.runInContext('globalVar *= 2;', sandbox);\n}\nconsole.log(util.inspect(sandbox));\n\n// { globalVar: 1024 }\nThe vm.runInNewContext() first contextifies the given sandbox object (or\ncreates a new sandbox if passed as undefined), compiles the code, runs it\nwithin the context of the created context, then returns the result. Running code\ndoes not have access to the local scope.
If options is a string, then it specifies the filename.
The following example compiles and executes code that increments a global\nvariable and sets a new one. These globals are contained in the sandbox.
const util = require('util');\nconst vm = require('vm');\n\nconst sandbox = {\n animal: 'cat',\n count: 2\n};\n\nvm.runInNewContext('count += 1; name = \"kitty\"', sandbox);\nconsole.log(util.inspect(sandbox));\n\n// { animal: 'cat', count: 3, name: 'kitty' }\nvm.runInThisContext() compiles code, runs it within the context of the\ncurrent global and returns the result. Running code does not have access to\nlocal scope, but does have access to the current global object.
If options is a string, then it specifies the filename.
The following example illustrates using both vm.runInThisContext() and\nthe JavaScript eval() function to run the same code:
const vm = require('vm');\nlet localVar = 'initial value';\n\nconst vmResult = vm.runInThisContext('localVar = \"vm\";');\nconsole.log('vmResult:', vmResult);\nconsole.log('localVar:', localVar);\n\nconst evalResult = eval('localVar = \"eval\";');\nconsole.log('evalResult:', evalResult);\nconsole.log('localVar:', localVar);\n\n// vmResult: 'vm', localVar: 'initial value'\n// evalResult: 'eval', localVar: 'eval'\nBecause vm.runInThisContext() does not have access to the local scope,\nlocalVar is unchanged. In contrast, eval() does have access to the\nlocal scope, so the value localVar is changed. In this way\nvm.runInThisContext() is much like an indirect eval() call, e.g.\n(0,eval)('code').
When using either script.runInThisContext() or\nvm.runInThisContext(), the code is executed within the current V8 global\ncontext. The code passed to this VM context will have its own isolated scope.
In order to run a simple web server using the http module the code passed to\nthe context must either call require('http') on its own, or have a reference\nto the http module passed to it. For instance:
'use strict';\nconst vm = require('vm');\n\nconst code = `\n((require) => {\n const http = require('http');\n\n http.createServer((request, response) => {\n response.writeHead(200, { 'Content-Type': 'text/plain' });\n response.end('Hello World\\\\n');\n }).listen(8124);\n\n console.log('Server running at http://127.0.0.1:8124/');\n})`;\n\nvm.runInThisContext(code)(require);\nThe require() in the above case shares the state with the context it is\npassed from. This may introduce risks when untrusted code is executed, e.g.\naltering objects in the context in unwanted ways.
All JavaScript executed within Node.js runs within the scope of a \"context\".\nAccording to the V8 Embedder's Guide:
\n\n\nIn V8, a context is an execution environment that allows separate, unrelated,\nJavaScript applications to run in a single instance of V8. You must explicitly\nspecify the context in which you want any JavaScript code to be run.
\n
When the method vm.createContext() is called, the sandbox object that is\npassed in (or a newly created object if sandbox is undefined) is associated\ninternally with a new instance of a V8 Context. This V8 Context provides the\ncode run using the vm module's methods with an isolated global environment\nwithin which it can operate. The process of creating the V8 Context and\nassociating it with the sandbox object is what this document refers to as\n\"contextifying\" the sandbox.
Because of the internal mechanics of how the process.nextTick() queue and\nthe microtask queue that underlies Promises are implemented within V8 and\nNode.js, it is possible for code running within a context to \"escape\" the\ntimeout set using vm.runInContext(), vm.runInNewContext(), and\nvm.runInThisContext().
For example, the following code executed by vm.runInNewContext() with a\ntimeout of 5 milliseconds schedules an infinite loop to run after a promise\nresolves. The scheduled loop is never interrupted by the timeout:
const vm = require('vm');\n\nfunction loop() {\n while (1) console.log(Date.now());\n}\n\nvm.runInNewContext(\n 'Promise.resolve().then(loop);',\n { loop, console },\n { timeout: 5 }\n);\nThis issue also occurs when the loop() call is scheduled using\nthe process.nextTick() function.
This issue occurs because all contexts share the same microtask and nextTick\nqueues.
", "type": "module", "displayName": "Timeout limitations when using process.nextTick(), and Promises" } ], "type": "module", "displayName": "vm" }, { "textRaw": "Worker Threads", "name": "worker_threads", "introduced_in": "v10.5.0", "stability": 1, "stabilityText": "Experimental", "desc": "The worker module provides a way to create multiple environments running\non independent threads, and to create message channels between them. It\ncan be accessed using the --experimental-worker flag and:
const worker = require('worker_threads');\nWorkers are useful for performing CPU-intensive JavaScript operations; do not\nuse them for I/O, since Node.js’s built-in mechanisms for performing operations\nasynchronously already treat it more efficiently than Worker threads can.
\nWorkers, unlike child processes or when using the cluster module, can also\nshare memory efficiently by transferring ArrayBuffer instances or sharing\nSharedArrayBuffer instances between them.
const {\n Worker, isMainThread, parentPort, workerData\n} = require('worker_threads');\n\nif (isMainThread) {\n module.exports = async function parseJSAsync(script) {\n return new Promise((resolve, reject) => {\n const worker = new Worker(__filename, {\n workerData: script\n });\n worker.on('message', resolve);\n worker.on('error', reject);\n worker.on('exit', (code) => {\n if (code !== 0)\n reject(new Error(`Worker stopped with exit code ${code}`));\n });\n });\n };\n} else {\n const { parse } = require('some-js-parsing-library');\n const script = workerData;\n parentPort.postMessage(parse(script));\n}\nNote that this example spawns a Worker thread for each parse call.\nIn practice, it is strongly recommended to use a pool of Workers for these\nkinds of tasks, since the overhead of creating Workers would likely exceed the\nbenefit of handing the work off to it.
Is true if this code is not running inside of a Worker thread.
If this thread was spawned as a Worker, this will be a MessagePort\nallowing communication with the parent thread. Messages sent using\nparentPort.postMessage() will be available in the parent thread\nusing worker.on('message'), and messages sent from the parent thread\nusing worker.postMessage() will be available in this thread using\nparentPort.on('message').
An integer identifier for the current thread. On the corresponding worker object\n(if there is any), it is available as worker.threadId.
An arbitrary JavaScript value that contains a clone of the data passed\nto this thread’s Worker constructor.
Instances of the worker.MessageChannel class represent an asynchronous,\ntwo-way communications channel.\nThe MessageChannel has no methods of its own. new MessageChannel()\nyields an object with port1 and port2 properties, which refer to linked\nMessagePort instances.
const { MessageChannel } = require('worker_threads');\n\nconst { port1, port2 } = new MessageChannel();\nport1.on('message', (message) => console.log('received', message));\nport2.postMessage({ foo: 'bar' });\n// prints: received { foo: 'bar' } from the `port1.on('message')` listener\nInstances of the worker.MessagePort class represent one end of an\nasynchronous, two-way communications channel. It can be used to transfer\nstructured data, memory regions and other MessagePorts between different\nWorkers.
With the exception of MessagePorts being EventEmitters rather\nthan EventTargets, this implementation matches browser MessagePorts.
The 'close' event is emitted once either side of the channel has been\ndisconnected.
The 'message' event is emitted for any incoming message, containing the cloned\ninput of port.postMessage().
Listeners on this event will receive a clone of the value parameter as passed\nto postMessage() and no further arguments.
Disables further sending of messages on either side of the connection.\nThis method can be called when no further communication will happen over this\nMessagePort.
Sends a JavaScript value to the receiving side of this channel.\nvalue will be transferred in a way which is compatible with\nthe HTML structured clone algorithm. In particular, it may contain circular\nreferences and objects like typed arrays that the JSON API is not able\nto stringify.
transferList may be a list of ArrayBuffer and MessagePort objects.\nAfter transferring, they will not be usable on the sending side of the channel\nanymore (even if they are not contained in value). Unlike with\nchild processes, transferring handles such as network sockets is currently\nnot supported.
If value contains SharedArrayBuffer instances, those will be accessible\nfrom either thread. They cannot be listed in transferList.
value may still contain ArrayBuffer instances that are not in\ntransferList; in that case, the underlying memory is copied rather than moved.
Because the object cloning uses the structured clone algorithm,\nnon-enumerable properties, property accessors, and object prototypes are\nnot preserved. In particular, Buffer objects will be read as\nplain Uint8Arrays on the receiving side.
The message object will be cloned immediately, and can be modified after\nposting without having side effects.
\nFor more information on the serialization and deserialization mechanisms\nbehind this API, see the serialization API of the v8 module.
Opposite of unref(). Calling ref() on a previously unref()ed port will\nnot let the program exit if it's the only active handle left (the default\nbehavior). If the port is ref()ed, calling ref() again will have no effect.
If listeners are attached or removed using .on('message'), the port will\nbe ref()ed and unref()ed automatically depending on whether\nlisteners for the event exist.
Starts receiving messages on this MessagePort. When using this port\nas an event emitter, this will be called automatically once 'message'\nlisteners are attached.
Calling unref() on a port will allow the thread to exit if this is the only\nactive handle in the event system. If the port is already unref()ed calling\nunref() again will have no effect.
If listeners are attached or removed using .on('message'), the port will\nbe ref()ed and unref()ed automatically depending on whether\nlisteners for the event exist.
The Worker class represents an independent JavaScript execution thread.\nMost Node.js APIs are available inside of it.
Notable differences inside a Worker environment are:
\nprocess.stdin, process.stdout and process.stderr\nmay be redirected by the parent thread.require('worker_threads').isMainThread property is set to false.require('worker_threads').parentPort message port is available.process.exit() does not stop the whole program, just the single thread,\nand process.abort() is not available.process.chdir() and process methods that set group or user ids\nare not available.process.env is a read-only reference to the environment variables.process.title cannot be modified.process.on('...').worker.terminate()\nbeing invoked.Currently, the following differences also exist until they are addressed:
\ninspector module is not available yet.Creating Worker instances inside of other Workers is possible.
Like Web Workers and the cluster module, two-way communication can be\nachieved through inter-thread message passing. Internally, a Worker has a\nbuilt-in pair of MessagePorts that are already associated with each other\nwhen the Worker is created. While the MessagePort object on the parent side\nis not directly exposed, its functionalities are exposed through\nworker.postMessage() and the worker.on('message') event\non the Worker object for the parent thread.
To create custom messaging channels (which is encouraged over using the default\nglobal channel because it facilitates separation of concerns), users can create\na MessageChannel object on either thread and pass one of the\nMessagePorts on that MessageChannel to the other thread through a\npre-existing channel, such as the global one.
See port.postMessage() for more information on how messages are passed,\nand what kind of JavaScript values can be successfully transported through\nthe thread barrier.
const assert = require('assert');\nconst {\n Worker, MessageChannel, MessagePort, isMainThread, parentPort\n} = require('worker_threads');\nif (isMainThread) {\n const worker = new Worker(__filename);\n const subChannel = new MessageChannel();\n worker.postMessage({ hereIsYourPort: subChannel.port1 }, [subChannel.port1]);\n subChannel.port2.on('message', (value) => {\n console.log('received:', value);\n });\n} else {\n parentPort.once('message', (value) => {\n assert(value.hereIsYourPort instanceof MessagePort);\n value.hereIsYourPort.postMessage('the worker is sending this');\n value.hereIsYourPort.close();\n });\n}\nThe 'error' event is emitted if the worker thread throws an uncaught\nexception. In that case, the worker will be terminated.
The 'exit' event is emitted once the worker has stopped. If the worker\nexited by calling process.exit(), the exitCode parameter will be the\npassed exit code. If the worker was terminated, the exitCode parameter will\nbe 1.
The 'message' event is emitted when the worker thread has invoked\nrequire('worker_threads').parentPort.postMessage().\nSee the port.on('message') event for more details.
The 'online' event is emitted when the worker thread has started executing\nJavaScript code.
Send a message to the worker that will be received via\nrequire('worker_threads').parentPort.on('message').\nSee port.postMessage() for more details.
Opposite of unref(), calling ref() on a previously unref()ed worker will\nnot let the program exit if it's the only active handle left (the default\nbehavior). If the worker is ref()ed, calling ref() again will have\nno effect.
Stop all JavaScript execution in the worker thread as soon as possible.\ncallback is an optional function that is invoked once this operation is known\nto have completed.
Warning: Currently, not all code in the internals of Node.js is prepared to\nexpect termination at arbitrary points in time and may crash if it encounters\nthat condition. Consequently, only call .terminate() if it is known that the\nWorker thread is not accessing Node.js core modules other than what is exposed\nin the worker module.
Calling unref() on a worker will allow the thread to exit if this is the only\nactive handle in the event system. If the worker is already unref()ed calling\nunref() again will have no effect.
This is a readable stream which contains data written to process.stderr\ninside the worker thread. If stderr: true was not passed to the\nWorker constructor, then data will be piped to the parent thread's\nprocess.stderr stream.
If stdin: true was passed to the Worker constructor, this is a\nwritable stream. The data written to this stream will be made available in\nthe worker thread as process.stdin.
This is a readable stream which contains data written to process.stdout\ninside the worker thread. If stdout: true was not passed to the\nWorker constructor, then data will be piped to the parent thread's\nprocess.stdout stream.
An integer identifier for the referenced thread. Inside the worker thread,\nit is available as require('worker_threads').threadId.
The zlib module provides compression functionality implemented using Gzip and\nDeflate/Inflate, as well as Brotli. It can be accessed using:
const zlib = require('zlib');\nCompressing or decompressing a stream (such as a file) can be accomplished by\npiping the source stream data through a zlib stream into a destination stream:
const gzip = zlib.createGzip();\nconst fs = require('fs');\nconst inp = fs.createReadStream('input.txt');\nconst out = fs.createWriteStream('input.txt.gz');\n\ninp.pipe(gzip).pipe(out);\nIt is also possible to compress or decompress data in a single step:
\nconst input = '.................................';\nzlib.deflate(input, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString('base64'));\n } else {\n // handle error\n }\n});\n\nconst buffer = Buffer.from('eJzT0yMAAGTvBe8=', 'base64');\nzlib.unzip(buffer, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\n});\nNote that all zlib APIs except those that are explicitly synchronous use libuv's\nthreadpool. This can lead to surprising effects in some applications, such as\nsubpar performance (which can be mitigated by adjusting the pool size)\nand/or unrecoverable and catastrophic memory fragmentation.
", "type": "module", "displayName": "Threadpool Usage" }, { "textRaw": "Compressing HTTP requests and responses", "name": "compressing_http_requests_and_responses", "desc": "The zlib module can be used to implement support for the gzip, deflate\nand br content-encoding mechanisms defined by\nHTTP.
The HTTP Accept-Encoding header is used within an http request to identify\nthe compression encodings accepted by the client. The Content-Encoding\nheader is used to identify the compression encodings actually applied to a\nmessage.
The examples given below are drastically simplified to show the basic concept.\nUsing zlib encoding can be expensive, and the results ought to be cached.\nSee Memory Usage Tuning for more information on the speed/memory/compression\ntradeoffs involved in zlib usage.
// client request example\nconst zlib = require('zlib');\nconst http = require('http');\nconst fs = require('fs');\nconst request = http.get({ host: 'example.com',\n path: '/',\n port: 80,\n headers: { 'Accept-Encoding': 'br,gzip,deflate' } });\nrequest.on('response', (response) => {\n const output = fs.createWriteStream('example.com_index.html');\n\n switch (response.headers['content-encoding']) {\n case 'br':\n response.pipe(zlib.createBrotliDecompress()).pipe(output);\n break;\n // Or, just use zlib.createUnzip() to handle both of the following cases:\n case 'gzip':\n response.pipe(zlib.createGunzip()).pipe(output);\n break;\n case 'deflate':\n response.pipe(zlib.createInflate()).pipe(output);\n break;\n default:\n response.pipe(output);\n break;\n }\n});\n// server example\n// Running a gzip operation on every request is quite expensive.\n// It would be much more efficient to cache the compressed buffer.\nconst zlib = require('zlib');\nconst http = require('http');\nconst fs = require('fs');\nhttp.createServer((request, response) => {\n const raw = fs.createReadStream('index.html');\n let acceptEncoding = request.headers['accept-encoding'];\n if (!acceptEncoding) {\n acceptEncoding = '';\n }\n\n // Note: This is not a conformant accept-encoding parser.\n // See https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3\n if (/\\bdeflate\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'deflate' });\n raw.pipe(zlib.createDeflate()).pipe(response);\n } else if (/\\bgzip\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'gzip' });\n raw.pipe(zlib.createGzip()).pipe(response);\n } else if (/\\bbr\\b/.test(acceptEncoding)) {\n response.writeHead(200, { 'Content-Encoding': 'br' });\n raw.pipe(zlib.createBrotliCompress()).pipe(response);\n } else {\n response.writeHead(200, {});\n raw.pipe(response);\n }\n}).listen(1337);\nBy default, the zlib methods will throw an error when decompressing\ntruncated data. However, if it is known that the data is incomplete, or\nthe desire is to inspect only the beginning of a compressed file, it is\npossible to suppress the default error handling by changing the flushing\nmethod that is used to decompress the last chunk of input data:
// This is a truncated version of the buffer from the above examples\nconst buffer = Buffer.from('eJzT0yMA', 'base64');\n\nzlib.unzip(\n buffer,\n // For Brotli, the equivalent is zlib.constants.BROTLI_OPERATION_FLUSH.\n { finishFlush: zlib.constants.Z_SYNC_FLUSH },\n (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\n });\nThis will not change the behavior in other error-throwing situations, e.g.\nwhen the input data has an invalid format. Using this method, it will not be\npossible to determine whether the input ended prematurely or lacks the\nintegrity checks, making it necessary to manually check that the\ndecompressed result is valid.
", "type": "module", "displayName": "Compressing HTTP requests and responses" }, { "textRaw": "Flushing", "name": "flushing", "desc": "Calling .flush() on a compression stream will make zlib return as much\noutput as currently possible. This may come at the cost of degraded compression\nquality, but can be useful when data needs to be available as soon as possible.
In the following example, flush() is used to write a compressed partial\nHTTP response to the client:
const zlib = require('zlib');\nconst http = require('http');\n\nhttp.createServer((request, response) => {\n // For the sake of simplicity, the Accept-Encoding checks are omitted.\n response.writeHead(200, { 'content-encoding': 'gzip' });\n const output = zlib.createGzip();\n output.pipe(response);\n\n setInterval(() => {\n output.write(`The current time is ${Date()}\\n`, () => {\n // The data has been passed to zlib, but the compression algorithm may\n // have decided to buffer the data for more efficient compression.\n // Calling .flush() will make the data available as soon as the client\n // is ready to receive it.\n output.flush();\n });\n }, 1000);\n}).listen(1337);\nFrom zlib/zconf.h, modified to Node.js's usage:
The memory requirements for deflate are (in bytes):
\n\n(1 << (windowBits + 2)) + (1 << (memLevel + 9))\nThat is: 128K for windowBits = 15 + 128K for memLevel = 8\n(default values) plus a few kilobytes for small objects.
For example, to reduce the default memory requirements from 256K to 128K, the\noptions should be set to:
\nconst options = { windowBits: 14, memLevel: 7 };\nThis will, however, generally degrade compression.
\nThe memory requirements for inflate are (in bytes) 1 << windowBits.\nThat is, 32K for windowBits = 15 (default value) plus a few kilobytes\nfor small objects.
This is in addition to a single internal output slab buffer of size\nchunkSize, which defaults to 16K.
The speed of zlib compression is affected most dramatically by the\nlevel setting. A higher level will result in better compression, but\nwill take longer to complete. A lower level will result in less\ncompression, but will be much faster.
In general, greater memory usage options will mean that Node.js has to make\nfewer calls to zlib because it will be able to process more data on\neach write operation. So, this is another factor that affects the\nspeed, at the cost of memory usage.
There are equivalents to the zlib options for Brotli-based streams, although\nthese options have different ranges than the zlib ones:
\nlevel option matches Brotli’s BROTLI_PARAM_QUALITY option.windowBits option matches Brotli’s BROTLI_PARAM_LGWIN option.See below for more details on Brotli-specific options.
", "type": "misc", "displayName": "For Brotli-based streams" } ] }, { "textRaw": "Constants", "name": "Constants", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "type": "misc", "miscs": [ { "textRaw": "zlib constants", "name": "zlib_constants", "desc": "All of the constants defined in zlib.h are also defined on\nrequire('zlib').constants. In the normal course of operations, it will not be\nnecessary to use these constants. They are documented so that their presence is\nnot surprising. This section is taken almost directly from the\nzlib documentation. See https://zlib.net/manual.html#Constants for more\ndetails.
Previously, the constants were available directly from require('zlib'), for\ninstance zlib.Z_NO_FLUSH. Accessing the constants directly from the module is\ncurrently still possible but is deprecated.
Allowed flush values.
\nzlib.constants.Z_NO_FLUSHzlib.constants.Z_PARTIAL_FLUSHzlib.constants.Z_SYNC_FLUSHzlib.constants.Z_FULL_FLUSHzlib.constants.Z_FINISHzlib.constants.Z_BLOCKzlib.constants.Z_TREESReturn codes for the compression/decompression functions. Negative\nvalues are errors, positive values are used for special but normal\nevents.
\nzlib.constants.Z_OKzlib.constants.Z_STREAM_ENDzlib.constants.Z_NEED_DICTzlib.constants.Z_ERRNOzlib.constants.Z_STREAM_ERRORzlib.constants.Z_DATA_ERRORzlib.constants.Z_MEM_ERRORzlib.constants.Z_BUF_ERRORzlib.constants.Z_VERSION_ERRORCompression levels.
\nzlib.constants.Z_NO_COMPRESSIONzlib.constants.Z_BEST_SPEEDzlib.constants.Z_BEST_COMPRESSIONzlib.constants.Z_DEFAULT_COMPRESSIONCompression strategy.
\nzlib.constants.Z_FILTEREDzlib.constants.Z_HUFFMAN_ONLYzlib.constants.Z_RLEzlib.constants.Z_FIXEDzlib.constants.Z_DEFAULT_STRATEGYThere are several options and other constants available for Brotli-based\nstreams:
", "modules": [ { "textRaw": "Flush operations", "name": "flush_operations", "desc": "The following values are valid flush operations for Brotli-based streams:
\nzlib.constants.BROTLI_OPERATION_PROCESS (default for all operations)zlib.constants.BROTLI_OPERATION_FLUSH (default when calling .flush())zlib.constants.BROTLI_OPERATION_FINISH (default for the last chunk)zlib.constants.BROTLI_OPERATION_EMIT_METADATA
There are several options that can be set on Brotli encoders, affecting\ncompression efficiency and speed. Both the keys and the values can be accessed\nas properties of the zlib.constants object.
The most important options are:
\nBROTLI_PARAM_MODE
BROTLI_MODE_GENERIC (default)BROTLI_MODE_TEXT, adjusted for UTF-8 textBROTLI_MODE_FONT, adjusted for WOFF 2.0 fontsBROTLI_PARAM_QUALITY
BROTLI_MIN_QUALITY to BROTLI_MAX_QUALITY,\nwith a default of BROTLI_DEFAULT_QUALITY.BROTLI_PARAM_SIZE_HINT
0 for an unknown input size.The following flags can be set for advanced control over the compression\nalgorithm and memory usage tuning:
\nBROTLI_PARAM_LGWIN
BROTLI_MIN_WINDOW_BITS to BROTLI_MAX_WINDOW_BITS,\nwith a default of BROTLI_DEFAULT_WINDOW, or up to\nBROTLI_LARGE_MAX_WINDOW_BITS if the BROTLI_PARAM_LARGE_WINDOW flag\nis set.BROTLI_PARAM_LGBLOCK
BROTLI_MIN_INPUT_BLOCK_BITS to BROTLI_MAX_INPUT_BLOCK_BITS.BROTLI_PARAM_DISABLE_LITERAL_CONTEXT_MODELING
BROTLI_PARAM_LARGE_WINDOW
BROTLI_PARAM_NPOSTFIX
0 to BROTLI_MAX_NPOSTFIX.BROTLI_PARAM_NDIRECT
0 to 15 << NPOSTFIX in steps of 1 << NPOSTFIX.These advanced options are available for controlling decompression:
\nBROTLI_DECODER_PARAM_DISABLE_RING_BUFFER_REALLOCATION
BROTLI_DECODER_PARAM_LARGE_WINDOW
Each zlib-based class takes an options object. All options are optional.
Note that some options are only relevant when compressing, and are\nignored by the decompression classes.
\nflush <integer> Default: zlib.constants.Z_NO_FLUSHfinishFlush <integer> Default: zlib.constants.Z_FINISHchunkSize <integer> Default: 16 * 1024windowBits <integer>level <integer> (compression only)memLevel <integer> (compression only)strategy <integer> (compression only)dictionary <Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> (deflate/inflate only,\nempty dictionary by default)info <boolean> (If true, returns an object with buffer and engine.)See the description of deflateInit2 and inflateInit2 at\nhttps://zlib.net/manual.html#Advanced for more information on these.
Each Brotli-based class takes an options object. All options are optional.
flush <integer> Default: zlib.constants.BROTLI_OPERATION_PROCESSfinishFlush <integer> Default: zlib.constants.BROTLI_OPERATION_FINISHchunkSize <integer> Default: 16 * 1024params <Object> Key-value object containing indexed Brotli parameters.For example:
\nconst stream = zlib.createBrotliCompress({\n chunkSize: 32 * 1024,\n params: {\n [zlib.constants.BROTLI_PARAM_MODE]: zlib.constants.BROTLI_MODE_TEXT,\n [zlib.constants.BROTLI_PARAM_QUALITY]: 4,\n [zlib.constants.BROTLI_PARAM_SIZE_HINT]: fs.statSync(inputFile).size\n }\n});\nAll of these take a Buffer, TypedArray, DataView,\nArrayBuffer or string as the first argument, an optional second argument\nto supply options to the zlib classes and will call the supplied callback\nwith callback(error, result).
Every method has a *Sync counterpart, which accept the same arguments, but\nwithout a callback.
Compress a chunk of data with BrotliCompress.
Decompress a chunk of data with BrotliDecompress.
Compress a chunk of data with Deflate.
Compress a chunk of data with DeflateRaw.
Decompress a chunk of data with Gunzip.
Compress a chunk of data with Gzip.
Decompress a chunk of data with Inflate.
Decompress a chunk of data with InflateRaw.
Decompress a chunk of data with Unzip.
Compress data using the Brotli algorithm.
" }, { "textRaw": "Class: zlib.BrotliDecompress", "type": "class", "name": "zlib.BrotliDecompress", "meta": { "added": [ "v10.16.0" ], "changes": [] }, "desc": "Decompress data using the Brotli algorithm.
" }, { "textRaw": "Class: zlib.Deflate", "type": "class", "name": "zlib.Deflate", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using deflate.
" }, { "textRaw": "Class: zlib.DeflateRaw", "type": "class", "name": "zlib.DeflateRaw", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using deflate, and do not append a zlib header.
Decompress a gzip stream.
" }, { "textRaw": "Class: zlib.Gzip", "type": "class", "name": "zlib.Gzip", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Compress data using gzip.
" }, { "textRaw": "Class: zlib.Inflate", "type": "class", "name": "zlib.Inflate", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2595", "description": "A truncated input stream will now result in an `'error'` event." } ] }, "desc": "Decompress a deflate stream.
" }, { "textRaw": "Class: zlib.InflateRaw", "type": "class", "name": "zlib.InflateRaw", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v6.8.0", "pr-url": "https://github.com/nodejs/node/pull/8512", "description": "Custom dictionaries are now supported by `InflateRaw`." }, { "version": "v5.0.0", "pr-url": "https://github.com/nodejs/node/pull/2595", "description": "A truncated input stream will now result in an `'error'` event." } ] }, "desc": "Decompress a raw deflate stream.
" }, { "textRaw": "Class: zlib.Unzip", "type": "class", "name": "zlib.Unzip", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "desc": "Decompress either a Gzip- or Deflate-compressed stream by auto-detecting\nthe header.
" }, { "textRaw": "Class: zlib.ZlibBase", "type": "class", "name": "zlib.ZlibBase", "meta": { "added": [ "v0.5.8" ], "changes": [ { "version": "v10.16.0", "pr-url": "https://github.com/nodejs/node/pull/24939", "description": "This class was renamed from `Zlib` to `ZlibBase`." } ] }, "desc": "Not exported by the zlib module. It is documented here because it is the base\nclass of the compressor/decompressor classes.
This class inherits from stream.Transform, allowing zlib objects to be\nused in pipes and similar stream operations.
Deprecated alias for zlib.bytesWritten. This original name was chosen\nbecause it also made sense to interpret the value as the number of bytes\nread by the engine, but is inconsistent with other streams in Node.js that\nexpose values under these names.
The zlib.bytesWritten property specifies the number of bytes written to\nthe engine, before the bytes are processed (compressed or decompressed,\nas appropriate for the derived class).
Close the underlying handle.
" }, { "textRaw": "zlib.flush([kind, ]callback)", "type": "method", "name": "flush", "meta": { "added": [ "v0.5.8" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`kind` **Default:** `zlib.constants.Z_FULL_FLUSH` for zlib-based streams, `zlib.constants.BROTLI_OPERATION_FLUSH` for Brotli-based streams.", "name": "kind", "default": "`zlib.constants.Z_FULL_FLUSH` for zlib-based streams, `zlib.constants.BROTLI_OPERATION_FLUSH` for Brotli-based streams", "optional": true }, { "textRaw": "`callback` {Function}", "name": "callback", "type": "Function" } ] } ], "desc": "Flush pending data. Don't call this frivolously, premature flushes negatively\nimpact the effectiveness of the compression algorithm.
\nCalling this only flushes data from the internal zlib state, and does not\nperform flushing of any kind on the streams level. Rather, it behaves like a\nnormal call to .write(), i.e. it will be queued up behind other pending\nwrites and will only produce output when data is being read from the stream.
This function is only available for zlib-based streams, i.e. not Brotli.
\nDynamically update the compression level and compression strategy.\nOnly applicable to deflate algorithm.
" }, { "textRaw": "zlib.reset()", "type": "method", "name": "reset", "meta": { "added": [ "v0.7.0" ], "changes": [] }, "signatures": [ { "params": [] } ], "desc": "Reset the compressor/decompressor to factory defaults. Only applicable to\nthe inflate and deflate algorithms.
" } ] } ], "properties": [ { "textRaw": "zlib.constants", "name": "constants", "meta": { "added": [ "v7.0.0" ], "changes": [] }, "desc": "Provides an object enumerating Zlib-related constants.
" } ], "methods": [ { "textRaw": "zlib.createBrotliCompress([options])", "type": "method", "name": "createBrotliCompress", "meta": { "added": [ "v10.16.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`options` {brotli options}", "name": "options", "type": "brotli options", "optional": true } ] } ], "desc": "Creates and returns a new BrotliCompress object.
Creates and returns a new BrotliDecompress object.
Creates and returns a new Deflate object.
Creates and returns a new DeflateRaw object.
An upgrade of zlib from 1.2.8 to 1.2.11 changed behavior when windowBits\nis set to 8 for raw deflate streams. zlib would automatically set windowBits\nto 9 if was initially set to 8. Newer versions of zlib will throw an exception,\nso Node.js restored the original behavior of upgrading a value of 8 to 9,\nsince passing windowBits = 9 to zlib actually results in a compressed stream\nthat effectively uses an 8-bit window only.
Creates and returns a new Gunzip object.
Creates and returns a new Gzip object.
Creates and returns a new Inflate object.
Creates and returns a new InflateRaw object.
Creates and returns a new Unzip object.
Compress a chunk of data with BrotliCompress.
Decompress a chunk of data with BrotliDecompress.
Compress a chunk of data with Deflate.
Compress a chunk of data with DeflateRaw.
Decompress a chunk of data with Gunzip.
Compress a chunk of data with Gzip.
Decompress a chunk of data with Inflate.
Decompress a chunk of data with InflateRaw.
Decompress a chunk of data with Unzip.
A generic JavaScript Error object that does not denote any specific\ncircumstance of why the error occurred. Error objects capture a \"stack trace\"\ndetailing the point in the code at which the Error was instantiated, and may\nprovide a text description of the error.
For crypto only, Error objects will include the OpenSSL error stack in a\nseparate property called opensslErrorStack if it is available when the error\nis thrown.
All errors generated by Node.js, including all System and JavaScript errors,\nwill either be instances of, or inherit from, the Error class.
Creates a .stack property on targetObject, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace() was called.
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack; // similar to `new Error().stack`\nThe first line of the trace will be prefixed with\n${myObject.name}: ${myObject.message}.
The optional constructorOpt argument accepts a function. If given, all frames\nabove constructorOpt, including constructorOpt, will be omitted from the\ngenerated stack trace.
The constructorOpt argument is useful for hiding implementation\ndetails of error generation from an end user. For instance:
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would show up in the .stack property. By passing\n// the constructor, we omit that frame, and retain all frames below it.\nnew MyError().stack;\nThe Error.stackTraceLimit property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack or\nError.captureStackTrace(obj)).
The default value is 10 but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.
" }, { "textRaw": "`code` {string}", "type": "string", "name": "code", "desc": "The error.code property is a string label that identifies the kind of error.\nerror.code is the most stable way to identify an error. It will only change\nbetween major versions of Node.js. In contrast, error.message strings may\nchange between any versions of Node.js. See Node.js Error Codes for details\nabout specific codes.
The error.message property is the string description of the error as set by\ncalling new Error(message). The message passed to the constructor will also\nappear in the first line of the stack trace of the Error, however changing\nthis property after the Error object is created may not change the first\nline of the stack trace (for example, when error.stack is read before this\nproperty is changed).
const err = new Error('The message');\nconsole.error(err.message);\n// Prints: The message\nThe error.stack property is a string describing the point in the code at which\nthe Error was instantiated.
Error: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)\nThe first line is formatted as <error class name>: <error message>, and\nis followed by a series of stack frames (each line beginning with \"at \").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.
Frames are only generated for JavaScript functions. If, for example, execution\nsynchronously passes through a C++ addon function called cheetahify which\nitself calls a JavaScript function, the frame representing the cheetahify call\nwill not be present in the stack traces:
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // cheetahify *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster();\n// will throw:\n// /home/gbusey/file.js:6\n// throw new Error('oh no!');\n// ^\n// Error: oh no!\n// at speedy (/home/gbusey/file.js:6:11)\n// at makeFaster (/home/gbusey/file.js:5:3)\n// at Object.<anonymous> (/home/gbusey/file.js:10:1)\n// at Module._compile (module.js:456:26)\n// at Object.Module._extensions..js (module.js:474:10)\n// at Module.load (module.js:356:32)\n// at Function.Module._load (module.js:312:12)\n// at Function.Module.runMain (module.js:497:10)\n// at startup (node.js:119:16)\n// at node.js:906:3\nThe location information will be one of:
\nnative, if the frame represents a call internal to V8 (as in [].forEach).plain-filename.js:line:column, if the frame represents a call internal\nto Node.js./absolute/path/to/file.js:line:column, if the frame represents a call in\na user program, or its dependencies.The string representing the stack trace is lazily generated when the\nerror.stack property is accessed.
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit or the number of available frames on the current event\nloop tick.
System-level errors are generated as augmented Error instances, which are\ndetailed here.
Creates a new Error object and sets the error.message property to the\nprovided text message. If an object is passed as message, the text message\nis generated by calling message.toString(). The error.stack property will\nrepresent the point in the code at which new Error() was called. Stack traces\nare dependent on V8's stack trace API. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit, whichever is smaller.
A subclass of Error that indicates the failure of an assertion. For details,\nsee Class: assert.AssertionError.
A subclass of Error that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.
require('net').connect(-1);\n// throws \"RangeError: \"port\" option should be >= 0 and < 65536: -1\"\nNode.js will generate and throw RangeError instances immediately as a form\nof argument validation.
A subclass of Error that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.
While client code may generate and propagate these errors, in practice, only V8\nwill do so.
\ndoesNotExist;\n// throws ReferenceError, doesNotExist is not a variable in this program.\nUnless an application is dynamically generating and running code,\nReferenceError instances should always be considered a bug in the code\nor its dependencies.
A subclass of Error that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval, Function,\nrequire, or vm. These errors are almost always indicative of a broken\nprogram.
try {\n require('vm').runInThisContext('binary ! isNotOk');\n} catch (err) {\n // err will be a SyntaxError\n}\nSyntaxError instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.
A subclass of Error that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError.
require('url').parse(() => { });\n// throws TypeError, since it expected a string\nNode.js will generate and throw TypeError instances immediately as a form\nof argument validation.
Used to handle binary data. See the buffer section.
" }, { "textRaw": "clearImmediate(immediateObject)", "type": "global", "name": "clearImmediate", "meta": { "added": [ "v0.9.1" ], "changes": [] }, "desc": "clearImmediate is described in the timers section.
clearInterval is described in the timers section.
clearTimeout is described in the timers section.
Used to print to stdout and stderr. See the console section.
In browsers, the top-level scope is the global scope. This means that\nwithin the browser var something will define a new global variable. In\nNode.js this is different. The top-level scope is not the global scope;\nvar something inside a Node.js module will be local to that module.
The process object. See the process object section.
setImmediate is described in the timers section.
setInterval is described in the timers section.
setTimeout is described in the timers section.
The WHATWG URL class. See the URL section.
The WHATWG URLSearchParams class. See the URLSearchParams section.
The object that acts as the namespace for all W3C\nWebAssembly related functionality. See the\nMozilla Developer Network for usage and compatibility.
" }, { "textRaw": "Process", "name": "Process", "introduced_in": "v0.10.0", "type": "global", "desc": "The process object is a global that provides information about, and control\nover, the current Node.js process. As a global, it is always available to\nNode.js applications without using require().
The process object is an instance of EventEmitter.
The 'beforeExit' event is emitted when Node.js empties its event loop and has\nno additional work to schedule. Normally, the Node.js process will exit when\nthere is no work scheduled, but a listener registered on the 'beforeExit'\nevent can make asynchronous calls, and thereby cause the Node.js process to\ncontinue.
The listener callback function is invoked with the value of\nprocess.exitCode passed as the only argument.
The 'beforeExit' event is not emitted for conditions causing explicit\ntermination, such as calling process.exit() or uncaught exceptions.
The 'beforeExit' should not be used as an alternative to the 'exit' event\nunless the intention is to schedule additional work.
If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the 'disconnect' event will be emitted when\nthe IPC channel is closed.
The 'exit' event is emitted when the Node.js process is about to exit as a\nresult of either:
process.exit() method being called explicitly;There is no way to prevent the exiting of the event loop at this point, and once\nall 'exit' listeners have finished running the Node.js process will terminate.
The listener callback function is invoked with the exit code specified either\nby the process.exitCode property, or the exitCode argument passed to the\nprocess.exit() method.
process.on('exit', (code) => {\n console.log(`About to exit with code: ${code}`);\n});\nListener functions must only perform synchronous operations. The Node.js\nprocess will exit immediately after calling the 'exit' event listeners\ncausing any additional work still queued in the event loop to be abandoned.\nIn the following example, for instance, the timeout will never occur:
process.on('exit', (code) => {\n setTimeout(() => {\n console.log('This will not run');\n }, 0);\n});\nIf the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the 'message' event is emitted whenever a\nmessage sent by a parent process using childprocess.send() is received by\nthe child process.
The message goes through serialization and parsing. The resulting message might\nnot be the same as what is originally sent.
" }, { "textRaw": "Event: 'multipleResolves'", "type": "event", "name": "multipleResolves", "meta": { "added": [ "v10.12.0" ], "changes": [] }, "params": [ { "textRaw": "`type` {string} The error type. One of `'resolve'` or `'reject'`.", "name": "type", "type": "string", "desc": "The error type. One of `'resolve'` or `'reject'`." }, { "textRaw": "`promise` {Promise} The promise that resolved or rejected more than once.", "name": "promise", "type": "Promise", "desc": "The promise that resolved or rejected more than once." }, { "textRaw": "`value` {any} The value with which the promise was either resolved or rejected after the original resolve.", "name": "value", "type": "any", "desc": "The value with which the promise was either resolved or rejected after the original resolve." } ], "desc": "The 'multipleResolves' event is emitted whenever a Promise has been either:
This is useful for tracking errors in an application while using the promise\nconstructor. Otherwise such mistakes are silently swallowed due to being in a\ndead zone.
\nIt is recommended to end the process on such errors, since the process could be\nin an undefined state. While using the promise constructor make sure that it is\nguaranteed to trigger the resolve() or reject() functions exactly once per\ncall and never call both functions in the same call.
process.on('multipleResolves', (type, promise, reason) => {\n console.error(type, promise, reason);\n setImmediate(() => process.exit(1));\n});\n\nasync function main() {\n try {\n return await new Promise((resolve, reject) => {\n resolve('First call');\n resolve('Swallowed resolve');\n reject(new Error('Swallowed reject'));\n });\n } catch {\n throw new Error('Failed');\n }\n}\n\nmain().then(console.log);\n// resolve: Promise { 'First call' } 'Swallowed resolve'\n// reject: Promise { 'First call' } Error: Swallowed reject\n// at Promise (*)\n// at new Promise (<anonymous>)\n// at main (*)\n// First call\nThe 'rejectionHandled' event is emitted whenever a Promise has been rejected\nand an error handler was attached to it (using promise.catch(), for\nexample) later than one turn of the Node.js event loop.
The Promise object would have previously been emitted in an\n'unhandledRejection' event, but during the course of processing gained a\nrejection handler.
There is no notion of a top level for a Promise chain at which rejections can\nalways be handled. Being inherently asynchronous in nature, a Promise\nrejection can be handled at a future point in time — possibly much later than\nthe event loop turn it takes for the 'unhandledRejection' event to be emitted.
Another way of stating this is that, unlike in synchronous code where there is\nan ever-growing list of unhandled exceptions, with Promises there can be a\ngrowing-and-shrinking list of unhandled rejections.
\nIn synchronous code, the 'uncaughtException' event is emitted when the list of\nunhandled exceptions grows.
In asynchronous code, the 'unhandledRejection' event is emitted when the list\nof unhandled rejections grows, and the 'rejectionHandled' event is emitted\nwhen the list of unhandled rejections shrinks.
const unhandledRejections = new Map();\nprocess.on('unhandledRejection', (reason, promise) => {\n unhandledRejections.set(promise, reason);\n});\nprocess.on('rejectionHandled', (promise) => {\n unhandledRejections.delete(promise);\n});\nIn this example, the unhandledRejections Map will grow and shrink over time,\nreflecting rejections that start unhandled and then become handled. It is\npossible to record such errors in an error log, either periodically (which is\nlikely best for long-running application) or upon process exit (which is likely\nmost convenient for scripts).
The 'uncaughtException' event is emitted when an uncaught JavaScript\nexception bubbles all the way back to the event loop. By default, Node.js\nhandles such exceptions by printing the stack trace to stderr and exiting\nwith code 1, overriding any previously set process.exitCode.\nAdding a handler for the 'uncaughtException' event overrides this default\nbehavior. Alternatively, change the process.exitCode in the\n'uncaughtException' handler which will result in the process exiting with the\nprovided exit code. Otherwise, in the presence of such handler the process will\nexit with 0.
process.on('uncaughtException', (err, origin) => {\n fs.writeSync(\n process.stderr.fd,\n `Caught exception: ${err}\\n` +\n `Exception origin: ${origin}`\n );\n});\n\nsetTimeout(() => {\n console.log('This will still run.');\n}, 500);\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\nconsole.log('This will not run.');\nNote that 'uncaughtException' is a crude mechanism for exception handling\nintended to be used only as a last resort. The event should not be used as\nan equivalent to On Error Resume Next. Unhandled exceptions inherently mean\nthat an application is in an undefined state. Attempting to resume application\ncode without properly recovering from the exception can cause additional\nunforeseen and unpredictable issues.
Exceptions thrown from within the event handler will not be caught. Instead the\nprocess will exit with a non-zero exit code and the stack trace will be printed.\nThis is to avoid infinite recursion.
\nAttempting to resume normally after an uncaught exception can be similar to\npulling out of the power cord when upgrading a computer — nine out of ten\ntimes nothing happens - but the 10th time, the system becomes corrupted.
\nThe correct use of 'uncaughtException' is to perform synchronous cleanup\nof allocated resources (e.g. file descriptors, handles, etc) before shutting\ndown the process. It is not safe to resume normal operation after\n'uncaughtException'.
To restart a crashed application in a more reliable way, whether\n'uncaughtException' is emitted or not, an external monitor should be employed\nin a separate process to detect application failures and recover or restart as\nneeded.
The 'unhandledRejection' event is emitted whenever a Promise is rejected and\nno error handler is attached to the promise within a turn of the event loop.\nWhen programming with Promises, exceptions are encapsulated as \"rejected\npromises\". Rejections can be caught and handled using promise.catch() and\nare propagated through a Promise chain. The 'unhandledRejection' event is\nuseful for detecting and keeping track of promises that were rejected whose\nrejections have not yet been handled.
process.on('unhandledRejection', (reason, promise) => {\n console.log('Unhandled Rejection at:', promise, 'reason:', reason);\n // Application specific logging, throwing an error, or other logic here\n});\n\nsomePromise.then((res) => {\n return reportToUser(JSON.pasre(res)); // note the typo (`pasre`)\n}); // no `.catch()` or `.then()`\nThe following will also trigger the 'unhandledRejection' event to be\nemitted:
function SomeResource() {\n // Initially set the loaded status to a rejected promise\n this.loaded = Promise.reject(new Error('Resource not yet loaded!'));\n}\n\nconst resource = new SomeResource();\n// no .catch or .then on resource.loaded for at least a turn\nIn this example case, it is possible to track the rejection as a developer error\nas would typically be the case for other 'unhandledRejection' events. To\naddress such failures, a non-operational\n.catch(() => { }) handler may be attached to\nresource.loaded, which would prevent the 'unhandledRejection' event from\nbeing emitted.
The 'warning' event is emitted whenever Node.js emits a process warning.
A process warning is similar to an error in that it describes exceptional\nconditions that are being brought to the user's attention. However, warnings\nare not part of the normal Node.js and JavaScript error handling flow.\nNode.js can emit warnings whenever it detects bad coding practices that could\nlead to sub-optimal application performance, bugs, or security vulnerabilities.
\nprocess.on('warning', (warning) => {\n console.warn(warning.name); // Print the warning name\n console.warn(warning.message); // Print the warning message\n console.warn(warning.stack); // Print the stack trace\n});\nBy default, Node.js will print process warnings to stderr. The --no-warnings\ncommand-line option can be used to suppress the default console output but the\n'warning' event will still be emitted by the process object.
The following example illustrates the warning that is printed to stderr when\ntoo many listeners have been added to an event:
$ node\n> events.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> (node:38638) MaxListenersExceededWarning: Possible EventEmitter memory leak\ndetected. 2 foo listeners added. Use emitter.setMaxListeners() to increase limit\nIn contrast, the following example turns off the default warning output and\nadds a custom handler to the 'warning' event:
$ node --no-warnings\n> const p = process.on('warning', (warning) => console.warn('Do not do that!'));\n> events.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> Do not do that!\nThe --trace-warnings command-line option can be used to have the default\nconsole output for warnings include the full stack trace of the warning.
Launching Node.js using the --throw-deprecation command line flag will\ncause custom deprecation warnings to be thrown as exceptions.
Using the --trace-deprecation command line flag will cause the custom\ndeprecation to be printed to stderr along with the stack trace.
Using the --no-deprecation command line flag will suppress all reporting\nof the custom deprecation.
The *-deprecation command line flags only affect warnings that use the name\n'DeprecationWarning'.
See the process.emitWarning() method for issuing\ncustom or application-specific warnings.
Signal events will be emitted when the Node.js process receives a signal. Please\nrefer to signal(7) for a listing of standard POSIX signal names such as\n'SIGINT', 'SIGHUP', etc.
The signal handler will receive the signal's name ('SIGINT',\n'SIGTERM', etc.) as the first argument.
The name of each event will be the uppercase common name for the signal (e.g.\n'SIGINT' for SIGINT signals).
// Begin reading from stdin so the process does not exit.\nprocess.stdin.resume();\n\nprocess.on('SIGINT', () => {\n console.log('Received SIGINT. Press Control-D to exit.');\n});\n\n// Using a single function to handle multiple signals\nfunction handle(signal) {\n console.log(`Received ${signal}`);\n}\n\nprocess.on('SIGINT', handle);\nprocess.on('SIGTERM', handle);\n'SIGUSR1' is reserved by Node.js to start the debugger. It's possible to\ninstall a listener but doing so might interfere with the debugger.'SIGTERM' and 'SIGINT' have default handlers on non-Windows platforms that\nreset the terminal mode before exiting with code 128 + signal number. If one\nof these signals has a listener installed, its default behavior will be\nremoved (Node.js will no longer exit).'SIGPIPE' is ignored by default. It can have a listener installed.'SIGHUP' is generated on Windows when the console window is closed, and on\nother platforms under various similar conditions. See signal(7). It can have a\nlistener installed, however Node.js will be unconditionally terminated by\nWindows about 10 seconds later. On non-Windows platforms, the default\nbehavior of SIGHUP is to terminate Node.js, but once a listener has been\ninstalled its default behavior will be removed.'SIGTERM' is not supported on Windows, it can be listened on.'SIGINT' from the terminal is supported on all platforms, and can usually be\ngenerated with <Ctrl>+C (though this may be configurable). It is not\ngenerated when terminal raw mode is enabled.'SIGBREAK' is delivered on Windows when <Ctrl>+<Break> is pressed, on\nnon-Windows platforms it can be listened on, but there is no way to send or\ngenerate it.'SIGWINCH' is delivered when the console has been resized. On Windows, this\nwill only happen on write to the console when the cursor is being moved, or\nwhen a readable tty is used in raw mode.'SIGKILL' cannot have a listener installed, it will unconditionally\nterminate Node.js on all platforms.'SIGSTOP' cannot have a listener installed.'SIGBUS', 'SIGFPE', 'SIGSEGV' and 'SIGILL', when not raised\n artificially using kill(2), inherently leave the process in a state from\n which it is not safe to attempt to call JS listeners. Doing so might lead to\n the process hanging in an endless loop, since listeners attached using\n process.on() are called asynchronously and therefore unable to correct the\nunderlying problem.Windows does not support sending signals, but Node.js offers some emulation\nwith process.kill(), and subprocess.kill(). Sending signal 0 can\nbe used to test for the existence of a process. Sending SIGINT, SIGTERM,\nand SIGKILL cause the unconditional termination of the target process.
Node.js will normally exit with a 0 status code when no more async\noperations are pending. The following status codes are used in other\ncases:
1 Uncaught Fatal Exception - There was an uncaught exception,\nand it was not handled by a domain or an 'uncaughtException' event\nhandler.2 - Unused (reserved by Bash for builtin misuse)3 Internal JavaScript Parse Error - The JavaScript source code\ninternal in Node.js's bootstrapping process caused a parse error. This\nis extremely rare, and generally can only happen during development\nof Node.js itself.4 Internal JavaScript Evaluation Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process failed to\nreturn a function value when evaluated. This is extremely rare, and\ngenerally can only happen during development of Node.js itself.5 Fatal Error - There was a fatal unrecoverable error in V8.\nTypically a message will be printed to stderr with the prefix FATAL ERROR.6 Non-function Internal Exception Handler - There was an\nuncaught exception, but the internal fatal exception handler\nfunction was somehow set to a non-function, and could not be called.7 Internal Exception Handler Run-Time Failure - There was an\nuncaught exception, and the internal fatal exception handler\nfunction itself threw an error while attempting to handle it. This\ncan happen, for example, if an 'uncaughtException' or\ndomain.on('error') handler throws an error.8 - Unused. In previous versions of Node.js, exit code 8 sometimes\nindicated an uncaught exception.9 - Invalid Argument - Either an unknown option was specified,\nor an option requiring a value was provided without a value.10 Internal JavaScript Run-Time Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process threw an error\nwhen the bootstrapping function was called. This is extremely rare,\nand generally can only happen during development of Node.js itself.12 Invalid Debug Argument - The --inspect and/or --inspect-brk\noptions were set, but the port number chosen was invalid or unavailable.>128 Signal Exits - If Node.js receives a fatal signal such as\nSIGKILL or SIGHUP, then its exit code will be 128 plus the\nvalue of the signal code. This is a standard POSIX practice, since\nexit codes are defined to be 7-bit integers, and signal exits set\nthe high-order bit, and then contain the value of the signal code.\nFor example, signal SIGABRT has value 6, so the expected exit\ncode will be 128 + 6, or 134.The process.abort() method causes the Node.js process to exit immediately and\ngenerate a core file.
This feature is not available in Worker threads.
The process.chdir() method changes the current working directory of the\nNode.js process or throws an exception if doing so fails (for instance, if\nthe specified directory does not exist).
console.log(`Starting directory: ${process.cwd()}`);\ntry {\n process.chdir('/tmp');\n console.log(`New directory: ${process.cwd()}`);\n} catch (err) {\n console.error(`chdir: ${err}`);\n}\nThis feature is not available in Worker threads.
The process.cpuUsage() method returns the user and system CPU time usage of\nthe current process, in an object with properties user and system, whose\nvalues are microsecond values (millionth of a second). These values measure time\nspent in user and system code respectively, and may end up being greater than\nactual elapsed time if multiple CPU cores are performing work for this process.
The result of a previous call to process.cpuUsage() can be passed as the\nargument to the function, to get a diff reading.
const startUsage = process.cpuUsage();\n// { user: 38579, system: 6986 }\n\n// spin the CPU for 500 milliseconds\nconst now = Date.now();\nwhile (Date.now() - now < 500);\n\nconsole.log(process.cpuUsage(startUsage));\n// { user: 514883, system: 11226 }\nThe process.cwd() method returns the current working directory of the Node.js\nprocess.
console.log(`Current directory: ${process.cwd()}`);\nIf the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the process.disconnect() method will close the\nIPC channel to the parent process, allowing the child process to exit gracefully\nonce there are no other connections keeping it alive.
The effect of calling process.disconnect() is that same as calling the parent\nprocess's ChildProcess.disconnect().
If the Node.js process was not spawned with an IPC channel,\nprocess.disconnect() will be undefined.
The process.dlopen() method allows to dynamically load shared\nobjects. It is primarily used by require() to load\nC++ Addons, and should not be used directly, except in special\ncases. In other words, require() should be preferred over\nprocess.dlopen(), unless there are specific reasons.
The flags argument is an integer that allows to specify dlopen\nbehavior. See the os.constants.dlopen documentation for details.
If there are specific reasons to use process.dlopen() (for instance,\nto specify dlopen flags), it's often useful to use require.resolve()\nto look up the module's path.
An important drawback when calling process.dlopen() is that the module\ninstance must be passed. Functions exported by the C++ Addon will be accessible\nvia module.exports.
The example below shows how to load a C++ Addon, named as binding,\nthat exports a foo function. All the symbols will be loaded before\nthe call returns, by passing the RTLD_NOW constant. In this example\nthe constant is assumed to be available.
const os = require('os');\nprocess.dlopen(module, require.resolve('binding'),\n os.constants.dlopen.RTLD_NOW);\nmodule.exports.foo();\nThe process.emitWarning() method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n'warning' event.
// Emit a warning with a code and additional detail.\nprocess.emitWarning('Something happened!', {\n code: 'MY_WARNING',\n detail: 'This is some additional information'\n});\n// Emits:\n// (node:56338) [MY_WARNING] Warning: Something happened!\n// This is some additional information\nIn this example, an Error object is generated internally by\nprocess.emitWarning() and passed through to the\n'warning' handler.
process.on('warning', (warning) => {\n console.warn(warning.name); // 'Warning'\n console.warn(warning.message); // 'Something happened!'\n console.warn(warning.code); // 'MY_WARNING'\n console.warn(warning.stack); // Stack trace\n console.warn(warning.detail); // 'This is some additional information'\n});\nIf warning is passed as an Error object, the options argument is ignored.
The process.emitWarning() method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n'warning' event.
// Emit a warning using a string.\nprocess.emitWarning('Something happened!');\n// Emits: (node: 56338) Warning: Something happened!\n// Emit a warning using a string and a type.\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n// Emits: (node:56338) CustomWarning: Something Happened!\nprocess.emitWarning('Something happened!', 'CustomWarning', 'WARN001');\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\nIn each of the previous examples, an Error object is generated internally by\nprocess.emitWarning() and passed through to the 'warning'\nhandler.
process.on('warning', (warning) => {\n console.warn(warning.name);\n console.warn(warning.message);\n console.warn(warning.code);\n console.warn(warning.stack);\n});\nIf warning is passed as an Error object, it will be passed through to the\n'warning' event handler unmodified (and the optional type,\ncode and ctor arguments will be ignored):
// Emit a warning using an Error object.\nconst myWarning = new Error('Something happened!');\n// Use the Error name property to specify the type name\nmyWarning.name = 'CustomWarning';\nmyWarning.code = 'WARN001';\n\nprocess.emitWarning(myWarning);\n// Emits: (node:56338) [WARN001] CustomWarning: Something happened!\nA TypeError is thrown if warning is anything other than a string or Error\nobject.
Note that while process warnings use Error objects, the process warning\nmechanism is not a replacement for normal error handling mechanisms.
The following additional handling is implemented if the warning type is\n'DeprecationWarning':
--throw-deprecation command-line flag is used, the deprecation\nwarning is thrown as an exception rather than being emitted as an event.--no-deprecation command-line flag is used, the deprecation\nwarning is suppressed.--trace-deprecation command-line flag is used, the deprecation\nwarning is printed to stderr along with the full stack trace.As a best practice, warnings should be emitted only once per process. To do\nso, it is recommended to place the emitWarning() behind a simple boolean\nflag as illustrated in the example below:
function emitMyWarning() {\n if (!emitMyWarning.warned) {\n emitMyWarning.warned = true;\n process.emitWarning('Only warn once!');\n }\n}\nemitMyWarning();\n// Emits: (node: 56339) Warning: Only warn once!\nemitMyWarning();\n// Emits nothing\nThe process.exit() method instructs Node.js to terminate the process\nsynchronously with an exit status of code. If code is omitted, exit uses\neither the 'success' code 0 or the value of process.exitCode if it has been\nset. Node.js will not terminate until all the 'exit' event listeners are\ncalled.
To exit with a 'failure' code:
\nprocess.exit(1);\nThe shell that executed Node.js should see the exit code as 1.
Calling process.exit() will force the process to exit as quickly as possible\neven if there are still asynchronous operations pending that have not yet\ncompleted fully, including I/O operations to process.stdout and\nprocess.stderr.
In most situations, it is not actually necessary to call process.exit()\nexplicitly. The Node.js process will exit on its own if there is no additional\nwork pending in the event loop. The process.exitCode property can be set to\ntell the process which exit code to use when the process exits gracefully.
For instance, the following example illustrates a misuse of the\nprocess.exit() method that could lead to data printed to stdout being\ntruncated and lost:
// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exit(1);\n}\nThe reason this is problematic is because writes to process.stdout in Node.js\nare sometimes asynchronous and may occur over multiple ticks of the Node.js\nevent loop. Calling process.exit(), however, forces the process to exit\nbefore those additional writes to stdout can be performed.
Rather than calling process.exit() directly, the code should set the\nprocess.exitCode and allow the process to exit naturally by avoiding\nscheduling any additional work for the event loop:
// How to properly set the exit code while letting\n// the process exit gracefully.\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exitCode = 1;\n}\nIf it is necessary to terminate the Node.js process due to an error condition,\nthrowing an uncaught error and allowing the process to terminate accordingly\nis safer than calling process.exit().
In Worker threads, this function stops the current thread rather\nthan the current process.
The process.getegid() method returns the numerical effective group identity\nof the Node.js process. (See getegid(2).)
if (process.getegid) {\n console.log(`Current gid: ${process.getegid()}`);\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "process.geteuid()", "type": "method", "name": "geteuid", "meta": { "added": [ "v2.0.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "The process.geteuid() method returns the numerical effective user identity of\nthe process. (See geteuid(2).)
if (process.geteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "process.getgid()", "type": "method", "name": "getgid", "meta": { "added": [ "v0.1.31" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {Object}", "name": "return", "type": "Object" }, "params": [] } ], "desc": "The process.getgid() method returns the numerical group identity of the\nprocess. (See getgid(2).)
if (process.getgid) {\n console.log(`Current gid: ${process.getgid()}`);\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "process.getgroups()", "type": "method", "name": "getgroups", "meta": { "added": [ "v0.9.4" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer[]}", "name": "return", "type": "integer[]" }, "params": [] } ], "desc": "The process.getgroups() method returns an array with the supplementary group\nIDs. POSIX leaves it unspecified if the effective group ID is included but\nNode.js ensures it always is.
This function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "process.getuid()", "type": "method", "name": "getuid", "meta": { "added": [ "v0.1.28" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {integer}", "name": "return", "type": "integer" }, "params": [] } ], "desc": "The process.getuid() method returns the numeric user identity of the process.\n(See getuid(2).)
if (process.getuid) {\n console.log(`Current uid: ${process.getuid()}`);\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).
" }, { "textRaw": "process.hasUncaughtExceptionCaptureCallback()", "type": "method", "name": "hasUncaughtExceptionCaptureCallback", "meta": { "added": [ "v9.3.0" ], "changes": [] }, "signatures": [ { "return": { "textRaw": "Returns: {boolean}", "name": "return", "type": "boolean" }, "params": [] } ], "desc": "Indicates whether a callback has been set using\nprocess.setUncaughtExceptionCaptureCallback().
This is the legacy version of process.hrtime.bigint()\nbefore bigint was introduced in JavaScript.
The process.hrtime() method returns the current high-resolution real time\nin a [seconds, nanoseconds] tuple Array, where nanoseconds is the\nremaining part of the real time that can't be represented in second precision.
time is an optional parameter that must be the result of a previous\nprocess.hrtime() call to diff with the current time. If the parameter\npassed in is not a tuple Array, a TypeError will be thrown. Passing in a\nuser-defined array instead of the result of a previous call to\nprocess.hrtime() will lead to undefined behavior.
These times are relative to an arbitrary time in the\npast, and not related to the time of day and therefore not subject to clock\ndrift. The primary use is for measuring performance between intervals:
\nconst NS_PER_SEC = 1e9;\nconst time = process.hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n const diff = process.hrtime(time);\n // [ 1, 552 ]\n\n console.log(`Benchmark took ${diff[0] * NS_PER_SEC + diff[1]} nanoseconds`);\n // benchmark took 1000000552 nanoseconds\n}, 1000);\nThe bigint version of the process.hrtime() method returning the\ncurrent high-resolution real time in a bigint.
Unlike process.hrtime(), it does not support an additional time\nargument since the difference can just be computed directly\nby subtraction of the two bigints.
const start = process.hrtime.bigint();\n// 191051479007711n\n\nsetTimeout(() => {\n const end = process.hrtime.bigint();\n // 191052633396993n\n\n console.log(`Benchmark took ${end - start} nanoseconds`);\n // Benchmark took 1154389282 nanoseconds\n}, 1000);\nThe process.initgroups() method reads the /etc/group file and initializes\nthe group access list, using all groups of which the user is a member. This is\na privileged operation that requires that the Node.js process either have root\naccess or the CAP_SETGID capability.
Note that care must be taken when dropping privileges:
\nconsole.log(process.getgroups()); // [ 0 ]\nprocess.initgroups('bnoordhuis', 1000); // switch user\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000, 0 ]\nprocess.setgid(1000); // drop root gid\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000 ]\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.kill() method sends the signal to the process identified by\npid.
Signal names are strings such as 'SIGINT' or 'SIGHUP'. See Signal Events\nand kill(2) for more information.
This method will throw an error if the target pid does not exist. As a special\ncase, a signal of 0 can be used to test for the existence of a process.\nWindows platforms will throw an error if the pid is used to kill a process\ngroup.
Even though the name of this function is process.kill(), it is really just a\nsignal sender, like the kill system call. The signal sent may do something\nother than kill the target process.
process.on('SIGHUP', () => {\n console.log('Got SIGHUP signal.');\n});\n\nsetTimeout(() => {\n console.log('Exiting.');\n process.exit(0);\n}, 100);\n\nprocess.kill(process.pid, 'SIGHUP');\nWhen SIGUSR1 is received by a Node.js process, Node.js will start the\ndebugger. See Signal Events.
The process.memoryUsage() method returns an object describing the memory usage\nof the Node.js process measured in bytes.
For example, the code:
\nconsole.log(process.memoryUsage());\nWill generate:
\n\n{\n rss: 4935680,\n heapTotal: 1826816,\n heapUsed: 650472,\n external: 49879\n}\nheapTotal and heapUsed refer to V8's memory usage.\nexternal refers to the memory usage of C++ objects bound to JavaScript\nobjects managed by V8. rss, Resident Set Size, is the amount of space\noccupied in the main memory device (that is a subset of the total allocated\nmemory) for the process, which includes the heap, code segment and stack.
The heap is where objects, strings, and closures are stored. Variables are\nstored in the stack and the actual JavaScript code resides in the\ncode segment.
\nWhen using Worker threads, rss will be a value that is valid for the\nentire process, while the other fields will only refer to the current thread.
The process.nextTick() method adds the callback to the \"next tick queue\".\nOnce the current turn of the event loop turn runs to completion, all callbacks\ncurrently in the next tick queue will be called.
This is not a simple alias to setTimeout(fn, 0). It is much more\nefficient. It runs before any additional I/O events (including\ntimers) fire in subsequent ticks of the event loop.
console.log('start');\nprocess.nextTick(() => {\n console.log('nextTick callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// nextTick callback\nThis is important when developing APIs in order to give users the opportunity\nto assign event handlers after an object has been constructed but before any\nI/O has occurred:
\nfunction MyThing(options) {\n this.setupOptions(options);\n\n process.nextTick(() => {\n this.startDoingStuff();\n });\n}\n\nconst thing = new MyThing();\nthing.getReadyForStuff();\n\n// thing.startDoingStuff() gets called now, not before.\nIt is very important for APIs to be either 100% synchronous or 100%\nasynchronous. Consider this example:
\n// WARNING! DO NOT USE! BAD UNSAFE HAZARD!\nfunction maybeSync(arg, cb) {\n if (arg) {\n cb();\n return;\n }\n\n fs.stat('file', cb);\n}\nThis API is hazardous because in the following case:
\nconst maybeTrue = Math.random() > 0.5;\n\nmaybeSync(maybeTrue, () => {\n foo();\n});\n\nbar();\nIt is not clear whether foo() or bar() will be called first.
The following approach is much better:
\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n process.nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\n}\nThe next tick queue is completely drained on each pass of the event loop\nbefore additional I/O is processed. As a result, recursively setting\nnextTick() callbacks will block any I/O from happening, just like a\nwhile(true); loop.
If Node.js is spawned with an IPC channel, the process.send() method can be\nused to send messages to the parent process. Messages will be received as a\n'message' event on the parent's ChildProcess object.
If Node.js was not spawned with an IPC channel, process.send() will be\nundefined.
The message goes through serialization and parsing. The resulting message might\nnot be the same as what is originally sent.
" }, { "textRaw": "process.setegid(id)", "type": "method", "name": "setegid", "meta": { "added": [ "v2.0.0" ], "changes": [] }, "signatures": [ { "params": [ { "textRaw": "`id` {string|number} A group name or ID", "name": "id", "type": "string|number", "desc": "A group name or ID" } ] } ], "desc": "The process.setegid() method sets the effective group identity of the process.\n(See setegid(2).) The id can be passed as either a numeric ID or a group\nname string. If a group name is specified, this method blocks while resolving\nthe associated a numeric ID.
if (process.getegid && process.setegid) {\n console.log(`Current gid: ${process.getegid()}`);\n try {\n process.setegid(501);\n console.log(`New gid: ${process.getegid()}`);\n } catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.seteuid() method sets the effective user identity of the process.\n(See seteuid(2).) The id can be passed as either a numeric ID or a username\nstring. If a username is specified, the method blocks while resolving the\nassociated numeric ID.
if (process.geteuid && process.seteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n try {\n process.seteuid(501);\n console.log(`New uid: ${process.geteuid()}`);\n } catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.setgid() method sets the group identity of the process. (See\nsetgid(2).) The id can be passed as either a numeric ID or a group name\nstring. If a group name is specified, this method blocks while resolving the\nassociated numeric ID.
if (process.getgid && process.setgid) {\n console.log(`Current gid: ${process.getgid()}`);\n try {\n process.setgid(501);\n console.log(`New gid: ${process.getgid()}`);\n } catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.setgroups() method sets the supplementary group IDs for the\nNode.js process. This is a privileged operation that requires the Node.js\nprocess to have root or the CAP_SETGID capability.
The groups array can contain numeric group IDs, group names or both.
This function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.setuid(id) method sets the user identity of the process. (See\nsetuid(2).) The id can be passed as either a numeric ID or a username string.\nIf a username is specified, the method blocks while resolving the associated\nnumeric ID.
if (process.getuid && process.setuid) {\n console.log(`Current uid: ${process.getuid()}`);\n try {\n process.setuid(501);\n console.log(`New uid: ${process.getuid()}`);\n } catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}\nThis function is only available on POSIX platforms (i.e. not Windows or\nAndroid).\nThis feature is not available in Worker threads.
The process.setUncaughtExceptionCaptureCallback() function sets a function\nthat will be invoked when an uncaught exception occurs, which will receive the\nexception value itself as its first argument.
If such a function is set, the 'uncaughtException' event will\nnot be emitted. If --abort-on-uncaught-exception was passed from the\ncommand line or set through v8.setFlagsFromString(), the process will\nnot abort.
To unset the capture function,\nprocess.setUncaughtExceptionCaptureCallback(null) may be used. Calling this\nmethod with a non-null argument while another capture function is set will\nthrow an error.
Using this function is mutually exclusive with using the deprecated\ndomain built-in module.
The process.umask() method sets or returns the Node.js process's file mode\ncreation mask. Child processes inherit the mask from the parent process. Invoked\nwithout an argument, the current mask is returned, otherwise the umask is set to\nthe argument value and the previous mask is returned.
const newmask = 0o022;\nconst oldmask = process.umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`\n);\nThis feature is not available in Worker threads.
The process.uptime() method returns the number of seconds the current Node.js\nprocess has been running.
The return value includes fractions of a second. Use Math.floor() to get whole\nseconds.
The process.allowedNodeEnvironmentFlags property is a special,\nread-only Set of flags allowable within the NODE_OPTIONS\nenvironment variable.
process.allowedNodeEnvironmentFlags extends Set, but overrides\nSet.prototype.has to recognize several different possible flag\nrepresentations. process.allowedNodeEnvironmentFlags.has() will\nreturn true in the following cases:
-) or double (--) dashes; e.g.,\ninspect-brk for --inspect-brk, or r for -r.--v8-options) may replace\none or more non-leading dashes for an underscore, or vice-versa;\ne.g., --perf_basic_prof, --perf-basic-prof, --perf_basic-prof,\netc.=) characters; all\ncharacters after and including the first equals will be ignored;\ne.g., --stack-trace-limit=100.NODE_OPTIONS.When iterating over process.allowedNodeEnvironmentFlags, flags will\nappear only once; each will begin with one or more dashes. Flags\npassed through to V8 will contain underscores instead of non-leading\ndashes:
process.allowedNodeEnvironmentFlags.forEach((flag) => {\n // -r\n // --inspect-brk\n // --abort_on_uncaught_exception\n // ...\n});\nThe methods add(), clear(), and delete() of\nprocess.allowedNodeEnvironmentFlags do nothing, and will fail\nsilently.
If Node.js was compiled without NODE_OPTIONS support (shown in\nprocess.config), process.allowedNodeEnvironmentFlags will\ncontain what would have been allowable.
The process.arch property returns a string identifying the operating system\nCPU architecture for which the Node.js binary was compiled.
The current possible values are: 'arm', 'arm64', 'ia32', 'mips',\n'mipsel', 'ppc', 'ppc64', 's390', 's390x', 'x32', and 'x64'.
console.log(`This processor architecture is ${process.arch}`);\nThe process.argv property returns an array containing the command line\narguments passed when the Node.js process was launched. The first element will\nbe process.execPath. See process.argv0 if access to the original value of\nargv[0] is needed. The second element will be the path to the JavaScript\nfile being executed. The remaining elements will be any additional command line\narguments.
For example, assuming the following script for process-args.js:
// print process.argv\nprocess.argv.forEach((val, index) => {\n console.log(`${index}: ${val}`);\n});\nLaunching the Node.js process as:
\n$ node process-args.js one two=three four\nWould generate the output:
\n0: /usr/local/bin/node\n1: /Users/mjr/work/node/process-args.js\n2: one\n3: two=three\n4: four\nThe process.argv0 property stores a read-only copy of the original value of\nargv[0] passed when Node.js starts.
$ bash -c 'exec -a customArgv0 ./node'\n> process.argv[0]\n'/Volumes/code/external/node/out/Release/node'\n> process.argv0\n'customArgv0'\nIf the Node.js process was spawned with an IPC channel (see the\nChild Process documentation), the process.channel\nproperty is a reference to the IPC channel. If no IPC channel exists, this\nproperty is undefined.
The process.config property returns an Object containing the JavaScript\nrepresentation of the configure options used to compile the current Node.js\nexecutable. This is the same as the config.gypi file that was produced when\nrunning the ./configure script.
An example of the possible output looks like:
\n\n{\n target_defaults:\n { cflags: [],\n default_configuration: 'Release',\n defines: [],\n include_dirs: [],\n libraries: [] },\n variables:\n {\n host_arch: 'x64',\n node_install_npm: 'true',\n node_prefix: '',\n node_shared_cares: 'false',\n node_shared_http_parser: 'false',\n node_shared_libuv: 'false',\n node_shared_zlib: 'false',\n node_use_dtrace: 'false',\n node_use_openssl: 'true',\n node_shared_openssl: 'false',\n strict_aliasing: 'true',\n target_arch: 'x64',\n v8_use_snapshot: 'true'\n }\n}\nThe process.config property is not read-only and there are existing\nmodules in the ecosystem that are known to extend, modify, or entirely replace\nthe value of process.config.
If the Node.js process is spawned with an IPC channel (see the Child Process\nand Cluster documentation), the process.connected property will return\ntrue so long as the IPC channel is connected and will return false after\nprocess.disconnect() is called.
Once process.connected is false, it is no longer possible to send messages\nover the IPC channel using process.send().
The port used by Node.js's debugger when enabled.
\nprocess.debugPort = 5858;\nThe process.env property returns an object containing the user environment.\nSee environ(7).
An example of this object looks like:
\n\n{\n TERM: 'xterm-256color',\n SHELL: '/usr/local/bin/bash',\n USER: 'maciej',\n PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',\n PWD: '/Users/maciej',\n EDITOR: 'vim',\n SHLVL: '1',\n HOME: '/Users/maciej',\n LOGNAME: 'maciej',\n _: '/usr/local/bin/node'\n}\nIt is possible to modify this object, but such modifications will not be\nreflected outside the Node.js process. In other words, the following example\nwould not work:
\n$ node -e 'process.env.foo = \"bar\"' && echo $foo\nWhile the following will:
\nprocess.env.foo = 'bar';\nconsole.log(process.env.foo);\nAssigning a property on process.env will implicitly convert the value\nto a string. This behavior is deprecated. Future versions of Node.js may\nthrow an error when the value is not a string, number, or boolean.
process.env.test = null;\nconsole.log(process.env.test);\n// => 'null'\nprocess.env.test = undefined;\nconsole.log(process.env.test);\n// => 'undefined'\nUse delete to delete a property from process.env.
process.env.TEST = 1;\ndelete process.env.TEST;\nconsole.log(process.env.TEST);\n// => undefined\nOn Windows operating systems, environment variables are case-insensitive.
\nprocess.env.TEST = 1;\nconsole.log(process.env.test);\n// => 1\nprocess.env is read-only in Worker threads.
The process.execArgv property returns the set of Node.js-specific command-line\noptions passed when the Node.js process was launched. These options do not\nappear in the array returned by the process.argv property, and do not\ninclude the Node.js executable, the name of the script, or any options following\nthe script name. These options are useful in order to spawn child processes with\nthe same execution environment as the parent.
$ node --harmony script.js --version\nResults in process.execArgv:
['--harmony']\nAnd process.argv:
['/usr/local/bin/node', 'script.js', '--version']\nThe process.execPath property returns the absolute pathname of the executable\nthat started the Node.js process.
'/usr/local/bin/node'\nA number which will be the process exit code, when the process either\nexits gracefully, or is exited via process.exit() without specifying\na code.
Specifying a code to process.exit(code) will override any\nprevious setting of process.exitCode.
The process.mainModule property provides an alternative way of retrieving\nrequire.main. The difference is that if the main module changes at\nruntime, require.main may still refer to the original main module in\nmodules that were required before the change occurred. Generally, it's\nsafe to assume that the two refer to the same module.
As with require.main, process.mainModule will be undefined if there\nis no entry script.
The process.noDeprecation property indicates whether the --no-deprecation\nflag is set on the current Node.js process. See the documentation for\nthe 'warning' event and the\nemitWarning() method for more information about this\nflag's behavior.
The process.pid property returns the PID of the process.
console.log(`This process is pid ${process.pid}`);\nThe process.platform property returns a string identifying the operating\nsystem platform on which the Node.js process is running.
Currently possible values are:
\n'aix''darwin''freebsd''linux''openbsd''sunos''win32'console.log(`This platform is ${process.platform}`);\nThe value 'android' may also be returned if the Node.js is built on the\nAndroid operating system. However, Android support in Node.js\nis experimental.
The process.ppid property returns the PID of the current parent process.
console.log(`The parent process is pid ${process.ppid}`);\nThe process.release property returns an Object containing metadata related\nto the current release, including URLs for the source tarball and headers-only\ntarball.
process.release contains the following properties:
name <string> A value that will always be 'node' for Node.js. For\nlegacy io.js releases, this will be 'io.js'.sourceUrl <string> an absolute URL pointing to a .tar.gz file containing\nthe source code of the current release.headersUrl<string> an absolute URL pointing to a .tar.gz file containing\nonly the source header files for the current release. This file is\nsignificantly smaller than the full source file and can be used for compiling\nNode.js native add-ons.libUrl <string> an absolute URL pointing to a node.lib file matching the\narchitecture and version of the current release. This file is used for\ncompiling Node.js native add-ons. This property is only present on Windows\nbuilds of Node.js and will be missing on all other platforms.lts <string> a string label identifying the LTS label for this release.\nThis property only exists for LTS releases and is undefined for all other\nrelease types, including Current releases. Currently the valid values are:
'Argon' for the 4.x LTS line beginning with 4.2.0.'Boron' for the 6.x LTS line beginning with 6.9.0.'Carbon' for the 8.x LTS line beginning with 8.9.1.{\n name: 'node',\n lts: 'Argon',\n sourceUrl: 'https://nodejs.org/download/release/v4.4.5/node-v4.4.5.tar.gz',\n headersUrl: 'https://nodejs.org/download/release/v4.4.5/node-v4.4.5-headers.tar.gz',\n libUrl: 'https://nodejs.org/download/release/v4.4.5/win-x64/node.lib'\n}\nIn custom builds from non-release versions of the source tree, only the\nname property may be present. The additional properties should not be\nrelied upon to exist.
The process.stderr property returns a stream connected to\nstderr (fd 2). It is a net.Socket (which is a Duplex\nstream) unless fd 2 refers to a file, in which case it is\na Writable stream.
process.stderr differs from other Node.js streams in important ways. See\nnote on process I/O for more information.
The process.stdin property returns a stream connected to\nstdin (fd 0). It is a net.Socket (which is a Duplex\nstream) unless fd 0 refers to a file, in which case it is\na Readable stream.
process.stdin.setEncoding('utf8');\n\nprocess.stdin.on('readable', () => {\n let chunk;\n // Use a loop to make sure we read all available data.\n while ((chunk = process.stdin.read()) !== null) {\n process.stdout.write(`data: ${chunk}`);\n }\n});\n\nprocess.stdin.on('end', () => {\n process.stdout.write('end');\n});\nAs a Duplex stream, process.stdin can also be used in \"old\" mode that\nis compatible with scripts written for Node.js prior to v0.10.\nFor more information see Stream compatibility.
In \"old\" streams mode the stdin stream is paused by default, so one\nmust call process.stdin.resume() to read from it. Note also that calling\nprocess.stdin.resume() itself would switch stream to \"old\" mode.
The process.stdout property returns a stream connected to\nstdout (fd 1). It is a net.Socket (which is a Duplex\nstream) unless fd 1 refers to a file, in which case it is\na Writable stream.
For example, to copy process.stdin to process.stdout:
process.stdin.pipe(process.stdout);\nprocess.stdout differs from other Node.js streams in important ways. See\nnote on process I/O for more information.
process.stdout and process.stderr differ from other Node.js streams in\nimportant ways:
console.log() and console.error(),\nrespectively.Writes may be synchronous depending on what the stream is connected to\nand whether the system is Windows or POSIX:
\nThese behaviors are partly for historical reasons, as changing them would\ncreate backwards incompatibility, but they are also expected by some users.
\nSynchronous writes avoid problems such as output written with console.log() or\nconsole.error() being unexpectedly interleaved, or not written at all if\nprocess.exit() is called before an asynchronous write completes. See\nprocess.exit() for more information.
Warning: Synchronous writes block the event loop until the write has\ncompleted. This can be near instantaneous in the case of output to a file, but\nunder high system load, pipes that are not being read at the receiving end, or\nwith slow terminals or file systems, its possible for the event loop to be\nblocked often enough and long enough to have severe negative performance\nimpacts. This may not be a problem when writing to an interactive terminal\nsession, but consider this particularly careful when doing production logging to\nthe process output streams.
\nTo check if a stream is connected to a TTY context, check the isTTY\nproperty.
For instance:
\n$ node -p \"Boolean(process.stdin.isTTY)\"\ntrue\n$ echo \"foo\" | node -p \"Boolean(process.stdin.isTTY)\"\nfalse\n$ node -p \"Boolean(process.stdout.isTTY)\"\ntrue\n$ node -p \"Boolean(process.stdout.isTTY)\" | cat\nfalse\nSee the TTY documentation for more information.
", "type": "module", "displayName": "A note on process I/O" } ] }, { "textRaw": "`throwDeprecation` {boolean}", "type": "boolean", "name": "throwDeprecation", "meta": { "added": [ "v0.9.12" ], "changes": [] }, "desc": "The process.throwDeprecation property indicates whether the\n--throw-deprecation flag is set on the current Node.js process. See the\ndocumentation for the 'warning' event and the\nemitWarning() method for more information about this\nflag's behavior.
The process.title property returns the current process title (i.e. returns\nthe current value of ps). Assigning a new value to process.title modifies\nthe current value of ps.
When a new value is assigned, different platforms will impose different maximum\nlength restrictions on the title. Usually such restrictions are quite limited.\nFor instance, on Linux and macOS, process.title is limited to the size of the\nbinary name plus the length of the command line arguments because setting the\nprocess.title overwrites the argv memory of the process. Node.js v0.8\nallowed for longer process title strings by also overwriting the environ\nmemory but that was potentially insecure and confusing in some (rather obscure)\ncases.
The process.traceDeprecation property indicates whether the\n--trace-deprecation flag is set on the current Node.js process. See the\ndocumentation for the 'warning' event and the\nemitWarning() method for more information about this\nflag's behavior.
The process.version property returns the Node.js version string.
console.log(`Version: ${process.version}`);\nThe process.versions property returns an object listing the version strings of\nNode.js and its dependencies. process.versions.modules indicates the current\nABI version, which is increased whenever a C++ API changes. Node.js will refuse\nto load modules that were compiled against a different module ABI version.
console.log(process.versions);\nWill generate an object similar to:
\n\n{ http_parser: '2.7.0',\n node: '8.9.0',\n v8: '6.3.292.48-node.6',\n uv: '1.18.0',\n zlib: '1.2.11',\n ares: '1.13.0',\n modules: '60',\n nghttp2: '1.29.0',\n napi: '2',\n openssl: '1.0.2n',\n icu: '60.1',\n unicode: '10.0',\n cldr: '32.0',\n tz: '2016b' }\nThis variable may appear to be global but is not. See require().