{ "type": "module", "source": "doc/api/n-api.md", "introduced_in": "v8.0.0", "stability": 2, "stabilityText": "Stable", "miscs": [ { "textRaw": "N-API", "name": "N-API", "introduced_in": "v8.0.0", "type": "misc", "stability": 2, "stabilityText": "Stable", "desc": "
N-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 (for example, 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 ECMA-262 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\");\n
\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}\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>\n
\nthe libuv APIs which are also included with Node.js and available via
\n#include <uv.h>\n
\nthe V8 API available via
\n#include <v8.h>\n
\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>\n
\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>\n
\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>\n
\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>\n
\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-API versions are additive and versioned independently from Node.js.\nVersion 4 is an extension to version 3 in that it has all of the APIs\nfrom version 3 with some additions. This means that it is not necessary\nto recompile for new versions of Node.js which are\nlisted as supporting a later version.
\n\n | 1 | \n2 | \n3 | \n4 | \n
---|---|---|---|---|
v6.x | \n\n | \n | v6.14.2* | \n\n |
v8.x | \nv8.0.0* | \nv8.10.0* | \nv8.11.2 | \nv8.16.0 | \n
v9.x | \nv9.0.0* | \nv9.3.0* | \nv9.11.0* | \n\n |
v10.x | \n\n | \n | v10.0.0 | \n\n |
v11.x | \n\n | \n | v11.0.0 | \nv11.8.0 | \n
v12.x | \n\n | \n | \n | v12.0.0 | \n
* Indicates that the N-API version was released as experimental
\nThe N-APIs associated strictly with accessing ECMAScript features from native\ncode can be found separately in js_native_api.h
and js_native_api_types.h
.\nThe APIs defined in these headers are included in node_api.h
and\nnode_api_types.h
. The headers are structured in this way in order to allow\nimplementations of N-API outside of Node.js. For those implementations the\nNode.js specific APIs may not be applicable.
The Node.js-specific parts of an addon can be separated from the code that\nexposes the actual functionality to the JavaScript environment so that the\nlatter may be used with multiple implementations of N-API. In the example below,\naddon.c
and addon.h
refer only to js_native_api.h
. This ensures that\naddon.c
can be reused to compile against either the Node.js implementation of\nN-API or any implementation of N-API outside of Node.js.
addon_node.c
is a separate file that contains the Node.js specific entry point\nto the addon and which instantiates the addon by calling into addon.c
when the\naddon is loaded into a Node.js environment.
// addon.h\n#ifndef _ADDON_H_\n#define _ADDON_H_\n#include <js_native_api.h>\nnapi_value create_addon(napi_env env);\n#endif // _ADDON_H_\n
\n// addon.c\n#include \"addon.h\"\n\n#define NAPI_CALL(env, call) \\\n do { \\\n napi_status status = (call); \\\n if (status != napi_ok) { \\\n const napi_extended_error_info* error_info = NULL; \\\n napi_get_last_error_info((env), &error_info); \\\n bool is_pending; \\\n napi_is_exception_pending((env), &is_pending); \\\n if (!is_pending) { \\\n const char* message = (error_info->error_message == NULL) \\\n ? \"empty error message\" \\\n : error_info->error_message; \\\n napi_throw_error((env), NULL, message); \\\n return NULL; \\\n } \\\n } \\\n } while(0)\n\nstatic napi_value\nDoSomethingUseful(napi_env env, napi_callback_info info) {\n // Do something useful.\n return NULL;\n}\n\nnapi_value create_addon(napi_env env) {\n napi_value result;\n NAPI_CALL(env, napi_create_object(env, &result));\n\n napi_value exported_function;\n NAPI_CALL(env, napi_create_function(env,\n \"doSomethingUseful\",\n NAPI_AUTO_LENGTH,\n DoSomethingUseful,\n NULL,\n &exported_function));\n\n NAPI_CALL(env, napi_set_named_property(env,\n result,\n \"doSomethingUseful\",\n exported_function));\n\n return result;\n}\n
\n// addon_node.c\n#include <node_api.h>\n#include \"addon.h\"\n\nNAPI_MODULE_INIT() {\n // This function body is expected to return a `napi_value`.\n // The variables `napi_env env` and `napi_value exports` may be used within\n // the body, as they are provided by the definition of `NAPI_MODULE_INIT()`.\n return create_addon(env);\n}\n
",
"type": "misc",
"displayName": "N-API Version Matrix"
},
{
"textRaw": "Environment Life Cycle APIs",
"name": "environment_life_cycle_apis",
"stability": 1,
"stabilityText": "Experimental",
"desc": "Section 8.7 of the ECMAScript Language Specification defines the concept\nof an \"Agent\" as a self-contained environment in which JavaScript code runs.\nMultiple such Agents may be started and terminated either concurrently or in\nsequence by the process.
\nA Node.js environment corresponds to an ECMAScript Agent. In the main process,\nan environment is created at startup, and additional environments can be created\non separate threads to serve as worker threads. When Node.js is embedded in\nanother application, the main thread of the application may also construct and\ndestroy a Node.js environment multiple times during the life cycle of the\napplication process such that each Node.js environment created by the\napplication may, in turn, during its life cycle create and destroy additional\nenvironments as worker threads.
\nFrom the perspective of a native addon this means that the bindings it provides\nmay be called multiple times, from multiple contexts, and even concurrently from\nmultiple threads.
\nNative addons may need to allocate global state of which they make use during\ntheir entire life cycle such that the state must be unique to each instance of\nthe addon.
\nTo this env, N-API provides a way to allocate data such that its life cycle is\ntied to the life cycle of the Agent.
", "modules": [ { "textRaw": "napi_set_instance_data", "name": "napi_set_instance_data", "meta": { "added": [ "v12.8.0" ], "changes": [] }, "desc": "napi_status napi_set_instance_data(napi_env env,\n void* data,\n napi_finalize finalize_cb,\n void* finalize_hint);\n
\n[in] env
: The environment that the N-API call is invoked under.[in] data
: The data item to make available to bindings of this instance.[in] finalize_cb
: The function to call when the environment is being torn\ndown. The function receives data
so that it might free it.[in] finalize_hint
: Optional hint to pass to the finalize callback\nduring collection.Returns napi_ok
if the API succeeded.
This API associates data
with the currently running Agent. data
can later\nbe retrieved using napi_get_instance_data()
. Any existing data associated with\nthe currently running Agent which was set by means of a previous call to\nnapi_set_instance_data()
will be overwritten. If a finalize_cb
was provided\nby the previous call, it will not be called.
napi_status napi_get_instance_data(napi_env env,\n void** data);\n
\n[in] env
: The environment that the N-API call is invoked under.[out] data
: The data item that was previously associated with the currently\nrunning Agent by a call to napi_set_instance_data()
.Returns napi_ok
if the API succeeded.
This API retrieves data that was previously associated with the currently\nrunning Agent via napi_set_instance_data()
. If no data is set, the call will\nsucceed and data
will be set to NULL
.
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", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "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;\n
\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;\n
\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", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "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;\n
",
"type": "module",
"displayName": "napi_threadsafe_function_release_mode"
},
{
"textRaw": "napi_threadsafe_function_call_mode",
"name": "napi_threadsafe_function_call_mode",
"meta": {
"added": [
"v10.6.0"
],
"napiVersion": [
4
],
"changes": []
},
"desc": "A 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;\n
",
"type": "module",
"displayName": "napi_threadsafe_function_call_mode"
},
{
"textRaw": "N-API Memory Management types",
"name": "n-api_memory_management_types",
"modules": [
{
"textRaw": "napi_handle_scope",
"name": "napi_handle_scope",
"desc": "This 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_value
s 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", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "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", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "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", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "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", "meta": { "added": [ "v8.0.0" ], "napiVersion": [ 1 ], "changes": [] }, "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);\n
",
"type": "module",
"displayName": "napi_callback"
},
{
"textRaw": "napi_finalize",
"name": "napi_finalize",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "Function 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);\n
",
"type": "module",
"displayName": "napi_finalize"
},
{
"textRaw": "napi_async_execute_callback",
"name": "napi_async_execute_callback",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "Function pointer used with functions that support asynchronous\noperations. Callback functions must satisfy the following signature:
\ntypedef void (*napi_async_execute_callback)(napi_env env, void* data);\n
\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.\nAvoid using the napi_env
parameter in the execute callback as\nit will likely execute JavaScript.
Function pointer used with functions that support asynchronous\noperations. Callback functions must satisfy the following signature:
\ntypedef void (*napi_async_complete_callback)(napi_env env,\n napi_status status,\n void* data);\n
",
"type": "module",
"displayName": "napi_async_complete_callback"
},
{
"textRaw": "napi_threadsafe_function_call_js",
"name": "napi_threadsafe_function_call_js",
"meta": {
"added": [
"v10.6.0"
],
"napiVersion": [
4
],
"changes": []
},
"desc": "Function 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
\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", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "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};\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
\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]\n
\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]\n
",
"modules": [
{
"textRaw": "napi_throw",
"name": "napi_throw",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "NAPI_EXTERN napi_status napi_throw(napi_env env, napi_value error);\n
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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}\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}\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
\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
\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
\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
\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
\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
\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
\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
\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
\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);\n
\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);\n
\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);\n
\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)\n
\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);\n
\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}\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}\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}\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}\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;\n
\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\nFunction
s and Object
s 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;\n
\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
\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
\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
\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
.\nArrayBuffer
s 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
\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
\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
\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
\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
\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 ArrayBuffer
s 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
\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 Uint8Array
s.
napi_status napi_create_object(napi_env env, napi_value* result)\n
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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 int* sign_bit,\n size_t* word_count,\n uint64_t* words);\n
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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_t
napi_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;\n
\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;\n
\nIndexed properties can be set in a similar manner. Consider the following\nJavaScript snippet:
\nconst arr = [];\narr[123] = 'hello';\n
\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;\n
\nProperties can be retrieved using the APIs described in this section.\nConsider the following JavaScript snippet:
\nconst arr = [];\nconst value = arr[123];\n
\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;\n
\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});\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;\n
",
"modules": [
{
"textRaw": "Structures",
"name": "structures",
"modules": [
{
"textRaw": "napi_property_attributes",
"name": "napi_property_attributes",
"desc": "typedef 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;\n
\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;\n
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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 ECMA-262\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
\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}\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;\n
",
"type": "module",
"displayName": "napi_call_function"
},
{
"textRaw": "napi_create_function",
"name": "napi_create_function",
"meta": {
"added": [
"v8.0.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "napi_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
\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)\n
\nGiven the above code, the add-on can be used from JavaScript as follows:
\nconst myaddon = require('./addon');\nmyaddon.sayHello();\n
\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 Function
s 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
\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
\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
\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);\n
\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);\n
\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}\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
\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
\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
\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
\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
\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.\nAvoid using the napi_env
parameter in the execute callback as\nit will likely execute JavaScript.
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);\n
\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);\n
\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
\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
\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
\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. Once it returns successfully, this API must not be called again\nwith the same napi_async_work
item or the result will be undefined.
napi_status napi_cancel_async_work(napi_env env,\n napi_async_work work);\n
\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
\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
\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
\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
\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
\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
\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
\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
\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;\n
\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;\n
",
"modules": [
{
"textRaw": "napi_create_promise",
"name": "napi_create_promise",
"meta": {
"added": [
"v8.5.0"
],
"napiVersion": [
1
],
"changes": []
},
"desc": "napi_status napi_create_promise(napi_env env,\n napi_deferred* deferred,\n napi_value* promise);\n
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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
\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", "meta": { "added": [ "v10.6.0" ], "napiVersion": [ 4 ], "changes": [] }, "desc": "NAPI_EXTERN napi_status\nnapi_unref_threadsafe_function(napi_env env, napi_threadsafe_function func);\n
\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" } ] } ] }