#nodejs #node #js #module #native #idiomatic #write


easy way to write nodejs module using rust

2 stable releases

6.0.3 Feb 14, 2024
6.0.2 Feb 13, 2024

#15 in #idiomatic

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Easy way to write native Node.js module using idiomatic Rust

兼容华为鸿蒙ArkTS N-API


在原作者伟大作品的基础上,我做了三项工作使node-bindgen支持华为鸿蒙ArkTS N-API开发

  1. 将封装了nodejs N-API的内部子工程nj-sys·替换为·包装了【鸿蒙ArkTS N-API】的外部依赖项oh-napi-sys
    1. 一方面,node-bindgen原作者的代码设计非常科学合理,所以对核心模块*-sys crate的替换工作很省心。
    2. 另一方面,【鸿蒙ArkTS N-API】与nodejs N-API的相似度极高。所以,模块替换后的适配工作量少之又少。
  2. 添加【编译条件】 — 这算是一处适配点
    1. 原因:【C无符号长整类型unsigned long】在鸿蒙armv7架构上是32bit,而在鸿蒙aarch64x86_64架构上却是64bit。所以,若既不搞【条件编译】又不预备多套代码,那么rustc就会交叉编译失败。感谢Rust的【条件编译】语言支持,让Cpp开发都哭去吧!
    2. 打广告了:在该基建之上做鸿蒙ArkTS N-API开发的中国同胞们就不用再分心考虑这类【架构差异】的技术细节了。这些破事实在太糟心!
  3. 修改包名从node-bindgenohos-node-bindgen

就目前而言,【鸿蒙ArkTS N-API】与nodejs N-API大约是95%相似。但是,我相信随着【鸿蒙操作系统】的后续发展,ArkTS N-API会引入越来越多与外国同类产品(比如,nodejs / Deno)不同的内容。



  1. 不再需要向[build-dependencies]配置表添加node-bindgen = { version = "6.0", default-features = false, features = ["build"] }依赖项了,因为【编译时链接】已完全委托给外部依赖项oh-napi-sys完成了。

  2. 输出链接库的编码格式不再是cdylib,而是dylib。即,

    crate-type = ["dylib"]


起因是ohos-node-bindgen的间接依赖项socket2 v0.4.10不兼容【华为鸿蒙操作系统】(— 别急,有得解)。依赖图如下

socket2 v0.4.10
├── async-io v1.13.0
   ├── async-std v1.12.0
   │   └── fluvio-future v0.6.2
   │       └── nj-core v6.0.1
   │           └── ohos-node-bindgen v6.0.2


  1. 【我已做,大家不用做】我已经forksocket2@0.4.x分支,并解了其对【华为鸿蒙操作系统】的兼容缺陷。所以,

  2. 大家直接克隆我的fork版本至本地硬盘,和切分支至v0.4.x

    git clone git@github.com:stuartZhang/socket2.git
    git checkout v0.4.x
  3. 重写(Override)调用端工程的【依赖图】,以指示Cargo优先加载本地的socket2:0.4.10依赖项,而不是从crates.io下载。即,向Cargo.toml文件增补如下配置表

    socket2 = "0.4.10"
    socket2 = { path = "<指向 socket2 本地克隆复本的完整路径>" }

然后,就能绕过线上的残次socket2 crate和成功交叉编译了。


  • Easy: Just write idiomatic Rust code, node-bindgen take care of generating Node.js FFI wrapper codes.
  • Safe: Node.js arguments are checked automatically based on Rust types.
  • Async: Support Async Rust. Async codes are translated into Node.js promises.
  • Class: Rust struct can be accessed using Node.js classes.
  • Stream: Implement Node.js stream using Rust
  • N-API: Use Node.js N-API, which means you don't have to recompile your module.

Compatibility with Node.js version

This project uses the v8 of Node N-API. Please see following compatibility matrix.

Following OS are supported:

  • Linux
  • MacOs
  • Windows

Why node-bindgen?

Writing native node-js requires lots of boilerplate code. Node-bindgen generates external "C" glue code from rust code, including native module registration. node-bindgen make it writing node-js module easy and fun.

Getting started

CLI Installation

Install nj-cli command line, which will be used to generate the native library.

cargo install nj-cli

This is a one time step.

Configuring Cargo.toml

Add two dependencies to your projects' Cargo.toml.

Add node-bindgen as a regular dependency (as below):

node-bindgen = { version = "6.0" }

Then update crate type to dylib to generate node.js compatible native module:

crate-type = ["dylib"]

Finally, add build.rs at the top of the project with following content:

fn main() {


Here is a function that adds two numbers. Note that you don't need to worry about JS conversion.

use ohos_node_bindgen::derive::node_bindgen;

/// add two integer
fn sum(first: i32, second: i32) -> i32 {
    first + second

Building native library

To build node.js library, using nj-cli to build:

nj-cli build

This will generate Node.js module in "./dist" folder.

To build a release version:

nj-cli build --release

Watching ./src for Changes

While developing your native module, you may want to watch for file changes and run a command when a change occurs, for example cargo check or cargo build.

For this, we can use nj-cli watch.

nj-cli watch installs [if it does not exist] and passes arguments to cargo watch. By default, nj-cli watch will run cargo check against your ./src files.

To see all available methods for nj-cli watch, run the following command:

nj-cli watch -- --help

Using in Node.js

Then in the Node.js, rust function can be invoked as normal node.js function:

$ node
Welcome to Node.js v18.18.0.
Type ".help" for more information.
> let addon = require('./dist');
> addon.sum(2,3)


Function name or method can be renamed instead of default mapping

fn mul(first: i32,second: i32) -> i32 {
    first * second

Rust function mul is re-mapped as multiply

Optional argument

Argument can be skipped if it is marked as optional

fn sum(first: i32, second: Option<i32>) -> i32 {
    first + second.unwrap_or(0)

Then sum can be invoked as sum(10) or sum(10,20)


JS callback are mapped as Rust closure.

fn hello<F: Fn(String)>(first: f64, second: F) {

    let msg = format!("argument is: {}", first);


from node:

let addon = require('./dist');

  assert.equal(msg,"argument is: 2");
  console.log(msg);  // print out argument is 2

Callback are supported in Async rust as well.

Support for Async Rust

Async rust function is mapped to Node.js promise.

use std::time::Duration;
use flv_future_aio::time::sleep;
use ohos_node_bindgen::derive::node_bindgen;

async fn hello(arg: f64) -> f64 {
    println!("woke and adding 10.0");
    arg + 10.0
let addon = require('./dist');

addon.hello(5).then((val) => {
  console.log("future value is %s",val);

Struct serialization

Structs, including generic structs, can have have the to-JS conversion boilerplate autogenerated. Just apply the node_bindgen macro to your struct:

struct MyJson {
    some_name: String,
    a_number: i64

fn my_json() -> MyJson {
    MyJson {
        some_name: "John".to_owned(),
        a_number: 1337
let addon = require('./dist');
assert.deepStrictEqual(addon.my_json(), {
    someName: "John",
    aNumber: 1337

Note that the fields must implement ohos_node_bindgen::core::TryIntoJs themselves. Any references must also implement Clone. Field names will be converted to camelCase.


Enums will also have their JS representation autogenerated with the help of ohos_node_bindgen:

enum ErrorType {
    WithMessage(String, usize),
    WithFields {
        val: usize

fn with_message() -> ErrorType {
    ErrorType::WithMessage("test".to_owned(), 321)

fn with_fields() -> ErrorType {
    ErrorType::WithFields {
        val: 123

fn with_unit() -> ErrorType {
assert.deepStrictEqual(addon.withMessage(), {
    withMessage: ["test", 321n]
assert.deepStrictEqual(addon.withFields(), {
    withFields: {
        val: 123n
assert.deepStrictEqual(addon.withUnit(), "UnitErrorType")

Tuple variants will be converted into lists, struct variants converted to objects, and unit variants converted into strings matching the variant's name in PascalCase. Generics and references are supported, with the same caveats as for structs.

JavaScript class

JavaScript class is supported.

struct MyClass {
    val: f64,

impl MyClass {

    fn new(val: f64) -> Self {
        Self { val }

    fn plus_one(&self) -> f64 {
        self.val + 1.0

    fn value(&self) -> f64 {
let addon = require('./dist');
const assert = require('assert');

let obj = new addon.MyObject(10);
assert.equal(obj.value,10,"verify value works");

There are more features in the examples folder.

Preparing npm packages

Node module generated with node-bindgen can be used directly in any node JS project, just copied index.node into it. But in case of direct access to a module IDE will not highlight available functions, classes etc. Usually, this is not comfortable and makes the risks of potential bugs higher as soon as the public API of the node module is changed.

To create a full-fledged npm package with TypeScript types definitions and all necessary JavaScript wrappers can be used a crate tslink.

tslink crate generates files *.d.ts, *.js and package.json with a description of the npm module. Such package could be integrated into an end-project with minimal effort.

In addition, because tslink generates TypeScript types definitions, any changes on the native node module (index.node) will be highlighted by TypeScript compiler and it makes the risk of bugs (related to changed API or public data types) much lower.

For example,

#[macro_use] extern crate tslink;
use tslink::tslink;
use ohos_node_bindgen::derive::node_bindgen;

struct MyScruct {
    inc: i32,

impl MyScruct {
    pub fn new(inc: i32) -> Self {
        Self { inc }

    fn inc_my_number(&self, a: i32) -> i32 {
        a + self.inc

Would be represented (*.d.ts) as

export declare class MyStruct {
    constructor(inc: number);
    incMyNumber(a: number): number;

Pay your attention, call of #[tslink] should be always above of call #[ohos_node_bindgen].

Also, please note, node-bindgen by default applies snake case naming to methods. You should use #[tslink(snake_case_naming)] to consider this moment (see more on crate page).

tslink requires a configuration in Cargo.toml (section [tslink]) of the root of your project. A configuration should include a valid path to the native node module. By default node-bindgen creates index.node in ./dist folder of your root.

File: ./Cargo.toml (in a root of project):

node = "./dist/index.node"

Full example of usage tslink and node-bindgen is here.

See more API documentation on a tslink crate page.

Note. The node-bindgen's developers are not responsible for the correctness of the work tslink crate. All possible issues and feature requests related to tslink should be addressed to tslink's developers.


If you'd like to contribute to the project, please read our Contributing guide.


This project is licensed under the Apache license.


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