rclnodejs - The ROS 2 Client Library for JavaScript

ROS Distro*	Linux	Windows
Rolling
Humble
Iron

* rclnodejs development and maintenance is limited to the ROS 2 LTS releases and the Rolling development branch

rclnodejs is a Node.js client library for the Robot Operating System (ROS 2). It provides tooling and comprehensive JavaScript and TypeScript APIs for developing ROS 2 solutions capable of interoperating with ROS 2 nodes implemented in other languages such as C++ and Python.

Here's an example for creating a ROS 2 node that publishes a string message in a few lines of JavaScript.

const rclnodejs = require('rclnodejs');
rclnodejs.init().then(() => {
  const node = new rclnodejs.Node('publisher_example_node');
  const publisher = node.createPublisher('std_msgs/msg/String', 'topic');
  publisher.publish(`Hello ROS 2 from rclnodejs`);
  node.spin();
});

Documentation

• Installation
• rclnodejs-cli
• API Documentation
• Using TypeScript
• Examples
• Efficient Usage Tips
• FAQ and Known Issues
• Building from Scratch
• Contributing

Installation

Prerequisites

Before installing rclnodejs please ensure the following software is installed and configured on your system:

• Nodejs version >= 16.13.0.

• ROS 2 SDK for details. DON'T FORGET TO SOURCE THE ROS 2 SETUP FILE

Installing rclnodejs

Install the rclnodejs version that is compatible with your version of ROS 2 (see table below).

For the most current version of rclnodejs run:

npm i rclnodejs

To install a specific version of rclnodejs use:

npm i rclnodejs@x.y.z

• Note: to install rclnodejs from GitHub: add "rclnodejs":"RobotWebTools/rclnodejs#<branch>" to your package.json dependency section.

rclnodejs-cli

rclnodejs-cli is a companion project we recently launched to provide a commandline interface to a set of developer tools for working with this rclnodejs. You may find rclnodejs-cli particularly useful if you plan to create ROS 2 node(s) and launch files for working with multiple node orchestrations.

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Usage: rclnodejs [command] [options]

Options:
  -h, --help                               display help for command

Commands:
  create-package [options] <package-name>  Create a ROS2 package for Nodejs development.
  generate-ros-messages                    Generate JavaScript code from ROS2 IDL interfaces
  help [command]                           display help for command

API Documentation

API documentation is generated by jsdoc and can be viewed in the docs/ folder or online doc. To create a local copy of the documentation run npm run docs.

Using rclnodejs with TypeScript

rclnodejs API can be used in TypeScript projects. You can find the TypeScript declaration files (*.d.ts) in the types/ folder.

Your tsconfig.json file should include the following compiler options:

{
  "compilerOptions": {
    "module": "commonjs",
    "moduleResolution": "node",
    "target": "es6"
    // your additional options here
  }
}

Here's a short rclnodejs TypeScript example:

import * as rclnodejs from 'rclnodejs';
rclnodejs.init().then(() => {
  const node = new rclnodejs.Node('publisher_example_node');
  const publisher = node.createPublisher('std_msgs/msg/String', 'topic');
  publisher.publish(`Hello ROS 2 from rclnodejs`);
  node.spin();
});

The benefits of using TypeScript become evident when working with more complex use-cases. ROS messages are defined in the types/interfaces.d.ts module. This module is updated as part of the generate-ros-messages process described in the next section.

ROS2 Interface Message Generation (important)

ROS components communicate by sending and receiving messages described by the interface definition language (IDL). ROS client libraries such as rclnodejs are responsible for converting these IDL message descriptions into source code of their target language. For this, rclnodejs provides the npm binarygenerate-ros-messages script that reads the IDL message files of a ROS environment and generates corresponding JavaScript message interface files. Additionally, the tool generates the TypeScript interface.d.ts file containing declarations for each IDL message file.

Learn more about ROS interfaces and IDL here.

In the following example rclnodejs loads a generated JavaScript message file corresponding to the ROS `std_msgs/msg/String' definition.

import * as rclnodejs from 'rclnodejs';
let stringMsgObject = rclnodejs.createMessageObject('std_msgs/msg/String');
stringMsgObject.data = 'hello world';

Maintaining Generated JavaScript Message Files

Message files are generated as a post-install step of the rclnodejs installation process. Thereafter, you will need to manually run the rclnodejs message generation script when new ROS message packages are installed for which your ROS2-nodejs project has a dependency.

Running generate-ros-messages Utility

To run the generate-ros-messages script from your Nodejs package, use the npx utility included in your Nodejs installation.

npx generate-ros-messages

The newly generated JavaScript files can be found at <yourproject>/node_modules/rclnodejs/generated/.

Contributing

Please read the Contributing Guide before making a pull request.

Thank you to all the people who already contributed to rclnodejs!

License

This project abides by the Apache License 2.0.