node-addon-api

What is node-addon-api?

The node-addon-api package is a helper library for building Node.js Addons in C++. It provides a C++ API that abstracts away the complexities of working with the low-level V8 and N-API provided by Node.js, making it easier to develop native addons.

What are node-addon-api's main functionalities?

Object Wrapping

Object wrapping allows C++ classes to be represented as JavaScript objects. It provides an easy way to create and manage objects that have a one-to-one relationship with C++ objects.

Napi::ObjectReference MyClass::constructor;

MyClass::MyClass(const Napi::CallbackInfo& info) : Napi::ObjectWrap<MyClass>(info) {
  // constructor implementation
}

Napi::Object MyClass::Init(Napi::Env env, Napi::Object exports) {
  Napi::HandleScope scope(env);

  Napi::Function func = DefineClass(env, "MyClass", {
    InstanceMethod("myMethod", &MyClass::MyMethod)
  });

  constructor = Napi::Persistent(func);
  constructor.SuppressDestruct();

  exports.Set("MyClass", func);
  return exports;
}

Function Arguments

The package provides a way to handle function arguments passed from JavaScript to C++ with type checking and conversion utilities.

Napi::Value MyFunction(const Napi::CallbackInfo& info) {
  Napi::Env env = info.Env();
  if (info.Length() < 2) {
    Napi::TypeError::New(env, "Expected at least two arguments").ThrowAsJavaScriptException();
  }

  Napi::String arg0 = info[0].As<Napi::String>();
  double arg1 = info[1].As<Napi::Number>().DoubleValue();

  // function implementation

  return Napi::String::New(env, "result");
}

Asynchronous Operations

node-addon-api provides utilities for performing asynchronous operations, allowing long-running tasks to be executed without blocking the Node.js event loop.

class MyAsyncWorker : public Napi::AsyncWorker {
public:
  MyAsyncWorker(Napi::Function& callback) : AsyncWorker(callback) {}

  void Execute() override {
    // Do work in another thread
  }

  void OnOK() override {
    Napi::HandleScope scope(Env());
    Callback().Call({Env().Null(), Napi::String::New(Env(), "Success")});
  }
};

Napi::Value RunAsyncWork(const Napi::CallbackInfo& info) {
  Napi::Function callback = info[0].As<Napi::Function>();
  MyAsyncWorker* worker = new MyAsyncWorker(callback);
  worker->Queue();
  return info.Env().Undefined();
}

Other packages similar to node-addon-api

nan

The 'nan' package is a header file filled with macros and utilities for making addon development for different versions of V8 easier. It predates N-API and node-addon-api, and while it's still used, node-addon-api is recommended for most cases due to its simpler API and direct support for N-API.

ffi-napi

The 'ffi-napi' package allows for calling foreign functions of dynamic libraries from Node.js. It is similar to node-addon-api in that it allows for native functionality in Node.js, but it focuses on interfacing with existing libraries rather than writing new native modules.

neon

The 'neon' package is a Rust framework for writing safe and fast native Node.js modules. Like node-addon-api, it simplifies the process of writing native addons but does so using Rust instead of C++.

README

node-addon-api module

This module contains header-only C++ wrapper classes which simplify the use of the C based N-API provided by Node.js when using C++. It provides a C++ object model and exception handling semantics with low overhead.

N-API is an ABI stable C interface provided by Node.js for building native addons. It is independent from the underlying JavaScript runtime (e.g. V8 or ChakraCore) and is maintained as part of Node.js itself. It is intended to insulate native addons from changes in the underlying JavaScript engine and allow modules compiled for one version to run on later versions of Node.js without recompilation.

The node-addon-api module, which is not part of Node.js, preserves the benefits of the N-API as it consists only of inline code that depends only on the stable API provided by N-API. As such, modules built against one version of Node.js using node-addon-api should run without having to be rebuilt with newer versions of Node.js.

It is important to remember that other Node.js interfaces such as libuv (included in a project via #include <uv.h>) are not ABI-stable across Node.js major versions. Thus, an addon must use N-API and/or node-addon-api exclusively and build against a version of Node.js that includes an implementation of N-API (meaning a version of Node.js newer than 6.14.2) in order to benefit from ABI stability across Node.js major versions. Node.js provides an ABI stability guide containing a detailed explanation of ABI stability in general, and the N-API ABI stability guarantee in particular.

As new APIs are added to N-API, node-addon-api must be updated to provide wrappers for those new APIs. For this reason node-addon-api provides methods that allow callers to obtain the underlying N-API handles so direct calls to N-API and the use of the objects/methods provided by node-addon-api can be used together. For example, in order to be able to use an API for which the node-addon-api does not yet provide a wrapper.

APIs exposed by node-addon-api are generally used to create and manipulate JavaScript values. Concepts and operations generally map to ideas specified in the ECMA262 Language Specification.

• Setup
• API Documentation
• Examples
• Tests
• More resource and info about native Addons
• Code of Conduct
• Contributors
• License

Current version: 2.0.2

(See CHANGELOG.md for complete Changelog)

Setup

• Installation and usage
• node-gyp
• cmake-js
• Conversion tool
• Checker tool
• Generator
• Prebuild tools

API Documentation

The following is the documentation for node-addon-api.

• Basic Types
  • Array
  • Symbol
  • String
  • Name
  • Number
  • Date
  • BigInt
  • Boolean
  • Env
  • Value
  • CallbackInfo
  • Reference
  • External
  • Object
    • ObjectReference
    • PropertyDescriptor
• Error Handling
  • Error
  • TypeError
  • RangeError
• Object Lifetime Management
  • HandleScope
  • EscapableHandleScope
• Working with JavaScript Values
  • Function
    • FunctionReference
  • ObjectWrap
    • ClassPropertyDescriptor
  • Buffer
  • ArrayBuffer
  • TypedArray
    • TypedArrayOf
  • DataView
• Memory Management
• Async Operations
  • AsyncWorker
  • AsyncContext
  • AsyncProgressWorker
• Thread-safe Functions
• Promises
• Version management

Examples

Are you new to node-addon-api? Take a look at our examples

• Hello World
• Pass arguments to a function
• Callbacks
• Object factory
• Function factory
• Wrapping C++ Object
• Factory of wrapped object
• Passing wrapped object around

Tests

To run the node-addon-api tests do:

npm install
npm test

To avoid testing the deprecated portions of the API run

npm install
npm test --disable-deprecated

Debug

To run the node-addon-api tests with --debug option:

npm run-script dev

If you want faster build, you might use the following option:

npm run-script dev:incremental

Take a look and get inspired by our test suite

Contributing

We love contributions from the community to node-addon-api. See CONTRIBUTING.md for more details on our philosophy around extending this module.

More resource and info about native Addons

• C++ Addons
• N-API
• N-API - Next Generation Node API for Native Modules

WG Members / Collaborators

Active

Name	GitHub Link
Anna Henningsen	addaleax
Gabriel Schulhof	gabrielschulhof
Hitesh Kanwathirtha	digitalinfinity
Jim Schlight	jschlight
Michael Dawson	mhdawson
Kevin Eady	KevinEady
Nicola Del Gobbo	NickNaso

Emeritus

Name	GitHub Link
Arunesh Chandra	aruneshchandra
Benjamin Byholm	kkoopa
Jason Ginchereau	jasongin
Sampson Gao	sampsongao
Taylor Woll	boingoing

Licensed under MIT