1 stable release

1.7.6 Aug 30, 2021

#225 in Concurrency

MIT license

6.5K SLoC


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This project was initialized from xray

A minimal library for building compiled Node.js add-ons in Rust.


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Platform Support

Lint Linux N-API@3 Linux musl macOS/Windows/Linux x64 Linux-aarch64 Linux-armv7 macOS-Android Windows i686 Windows arm64 FreeBSD

node12 node14 node16
Windows x64
Windows x86
Windows arm64
macOS x64
macOS aarch64
Linux x64 gnu
Linux x64 musl
Linux aarch64 gnu
Linux aarch64 musl
Linux arm gnueabihf
Linux aarch64 android
FreeBSD x64

This library depends on Node-API and requires Node@10.0.0 or later.

We already have some packages written by napi-rs: node-rs

One nice feature is that this crate allows you to build add-ons purely with the Rust/JavaScript toolchain and without involving node-gyp.


You can start from package-template to play with napi-rs

Define JavaScript functions

#[js_function(1)] // ------> arguments length
fn fibonacci(ctx: CallContext) -> Result<JsNumber> {
  let n = ctx.get::<JsNumber>(0)?.try_into()?;

fn fibonacci_native(n: i64) -> i64 {
  match n {
    1 | 2 => 1,
    _ => fibonacci_native(n - 1) + fibonacci_native(n - 2),

Register module

extern crate napi_derive;

use napi::{JsObject, Result};

/// `exports` is `module.exports` object in NodeJS
fn init(mut exports: JsObject) -> Result<()> {
  exports.create_named_method("fibonacci", fibonacci)?;

And you can also create JavaScript value while registering module:

extern crate napi_derive;

use napi::{JsObject, Result, Env};

fn init(mut exports: JsObject, env: Env) -> Result<()> {
  exports.create_named_method("fibonacci", fibonacci)?;
  exports.set_named_property("DEFAULT_VALUE", env.create_int64(100)?)?;


This repository is a Cargo crate. Any napi-based add-on should contain Cargo.toml to make it a Cargo crate.

In your Cargo.toml you need to set the crate-type to "cdylib" so that cargo builds a C-style shared library that can be dynamically loaded by the Node executable. You'll also need to add this crate as a dependency.

name = "awesome"

crate-type = ["cdylib"]

napi = "1"
napi-derive = "1"

napi-build = "1"

And create build.rs in your own project:

// build.rs
extern crate napi_build;

fn main() {

So far, the napi build script has only been tested on macOS Linux Windows x64 MSVC and FreeBSD.

See the included test_module for an example add-on.

Install the @napi-rs/cli to help you build your Rust codes and copy Dynamic lib file to .node file in case you can require it in your program.

  "package": "awesome-package",
  "devDependencies": {
    "@napi-rs/cli": "^1.0.0"
  "napi": {
    "name": "jarvis" // <----------- Config the name of native addon, or the napi command will use the name of `Cargo.toml` for the binary file name.
  "scripts": {
    "build": "napi build --release",
    "build:debug": "napi build"

Then you can require your native binding:


The module_name would be your package name in your Cargo.toml.

xxx => ./xxx.node

xxx-yyy => ./xxx_yyy.node

You can also copy Dynamic lib file to an appointed location:

napi build [--release] ./dll
napi build [--release] ./artifacts

There are documents which contains more details about the @napi-rs/cli usage.


Because libraries that depend on this crate must be loaded into a Node executable in order to resolve symbols, all tests are written in JavaScript in the test_module subdirectory.

To run tests:

yarn build:test
yarn test

Features table

Create JavaScript values

NAPI NAPI Version Minimal Node version Status
napi_create_array 1 v8.0.0
napi_create_array_with_length 1 v8.0.0
napi_create_arraybuffer 1 v8.0.0
napi_create_buffer 1 v8.0.0
napi_create_buffer_copy 1 v8.0.0
napi_create_date 5 v11.11.0
napi_create_external 1 v8.0.0
napi_create_external_arraybuffer 1 v8.0.0
napi_create_external_buffer 1 v8.0.0
napi_create_object 1 v8.0.0
napi_create_symbol 1 v8.0.0
napi_create_typedarray 1 v8.0.0
napi_create_dataview 1 v8.3.0
napi_create_int32 1 v8.4.0
napi_create_uint32 1 v8.4.0
napi_create_int64 1 v8.4.0
napi_create_double 1 v8.4.0
napi_create_bigint_int64 6 v10.7.0
napi_create_bigint_uint64 6 v10.7.0
napi_create_bigint_words 6 v10.7.0
napi_create_string_latin1 1 v8.0.0
napi_create_string_utf16 1 v8.0.0
napi_create_string_utf8 1 v8.0.0
napi_type_tag 8 v14.8.0, v12.19.0 ⚠️

I have no plan to implement nape_type_tag and related API in napi-rs, because we have implemented a rust replacement in TaggedObject which is more convenient and more compatible.

Functions to convert from Node-API to C types

NAPI NAPI Version Minimal Node Version Status
napi_get_array_length 1 v8.0.0
napi_get_arraybuffer_info 1 v8.0.0
napi_get_buffer_info 1 v8.0.0
napi_get_prototype 1 v8.0.0
napi_get_typedarray_info 1 v8.0.0
napi_get_dataview_info 1 v8.3.0
napi_get_date_value 5 v11.11.0
napi_get_value_bool 1 v8.0.0
napi_get_value_double 1 v8.0.0
napi_get_value_bigint_int64 6 v10.7.0
napi_get_value_bigint_uint64 6 v10.7.0
napi_get_value_bigint_words 6 v10.7.0
napi_get_value_external 1 v8.0.0
napi_get_value_int32 1 v8.0.0
napi_get_value_int64 1 v8.0.0
napi_get_value_string_latin1 1 v8.0.0
napi_get_value_string_utf8 1 v8.0.0
napi_get_value_string_utf16 1 v8.0.0
napi_get_value_uint32 1 v8.0.0
napi_get_boolean 1 v8.0.0
napi_get_global 1 v8.0.0
napi_get_null 1 v8.0.0
napi_get_undefined 1 v8.0.0

Working with JavaScript Values and Abstract Operations

NAPI NAPI Version Minimal Node Version Status
napi_coerce_to_bool 1 v8.0.0
napi_coerce_to_number 1 v8.0.0
napi_coerce_to_object 1 v8.0.0
napi_coerce_to_string 1 v8.0.0
napi_typeof 1 v8.0.0
napi_instanceof 1 v8.0.0
napi_is_array 1 v8.0.0
napi_is_arraybuffer 1 v8.0.0
napi_is_buffer 1 v8.0.0
napi_is_date 1 v8.0.0
napi_is_error 1 v8.0.0
napi_is_typedarray 1 v8.0.0
napi_is_dataview 1 v8.3.0
napi_strict_equals 1 v8.0.0
napi_detach_arraybuffer 7 v13.3.0
napi_is_detached_arraybuffer 7 v13.3.0
napi_object_freeze 8 v14.14.0, v12.20.0
napi_object_seal 8 v14.14.0, v12.20.0


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