Jass::React::JSX – React JSX support for the Rails asset pipeline

Jass::React::JSX enables Sprockets and the Rails asset pipeline to compile React JSX components.

JSX components will be compiled to ES modules, which can be imported using the new Rails Import Maps or regular <script module> tags.

Modern browsers support native loading of ES modules using the import statement. By leveraging the new Rails Import Maps, modular JS applications can be built without having to integrate a complex and tedious JS build pipeline.

However, framework-specific component formats like the React JSX format could not be used this way till now.

Jass::React::JSX enables the asset pipeline to compile .jsx files to ES modules, allowing to build modular React applications in a clear and straightforward way, without the necessity of external build tools.

gem 'jass-react-jsx'

Add the Babel transformers to your JS dependencies:

$ yarn add @babel/core @babel/plugin-transform-react-jsx

Jass::React::JSX depends on Nodo, which requires a working Node.js installation.

Place your .jsx components inside your regular app/javascript path.

In app/javascript/components/HelloWorld.jsx:

import { Component } from "react";

export default class HelloWorld extends Component {
  render() {
    return (
      <div>
        <h1>Hello, world!</h1>
        <h2>The current UNIX date is {Date.now()}.</h2>
      </div>
    );
  }
}

In your HTML code, load the component as a module:

<%= javascript_include_tag 'components/HelloWorld.js', module: true %>

In order to use module imports within your components, you need to pin them in your Rails importmap:

# config/importmap.rb
pin "react", to: "https://cdn.esm.sh/v45/react@17.0.2/es2021/react.js"
pin "react-dom", to: "https://cdn.esm.sh/v45/react-dom@17.0.2/es2021/react-dom.js"
pin "react/jsx-runtime", to: "https://cdn.esm.sh/v45/react@17.0.2/es2021/jsx-runtime.js"

pin "components/HelloWorld.jsx", to: "components/HelloWorld.js"

Then just use them in your JS code:

import { render } from "react-dom";
import HelloWorld from "components/HelloWorld.jsx";

For an example Rails application check out the example/reakt folder in this repo.

As of v0.8.1, the rails-importmap gem doesn't support globbing and reloading of JS modules with a file extension other than .js, therefore a modified version is provided at mtgrosser/importmap-rails.

To use the modified version of importmap-rails, add it to your Gemfile:

gem "importmap-rails", ">= 0.3.4", github: "mtgrosser/importmap-rails", branch: "main"

There is a pull request which will resolve this issue when accepted.

Also, the following things are not (yet) supported:

• source maps