$ yarn create react-app my-app -- --scripts-version reason-scripts

Reason Scripts provides a JS-like development environment for developing web apps with the Reason programming language and React. It bootstraps an environment to automatically compile all Reason code to JS, provide features like reloading and bundling, and seamlessly use JS code from Reason.

To create a new app using Reason and React, run:

$ npm install -g bs-platform
$ yarn create react-app <app-name> -- --scripts-version reason-scripts
$ cd <app-name>
$ yarn start

This will create a new app the the <app-name> directory with the following layout:

<app-name>/
  README.md
  node_modules/
  package.json
  bsconfig.json
  .gitignore
  public/
    favicon.ico
    index.html
  src/
    index.re
    index.css
    app.re
    app.css
    logo.svg

• Highly-optimized build configuration
• Pre-configured test runner
• Friendly developer environment
• "eject" Webpack config
• Environment variable configuration
• Automatic PWA configuration
• Low configuration builds

The entry point to the app is src/index.re. From the start your new app will be based on Reason, but can seamlessly interop with existing JS files and projects!

Any Reason file will be automatically compiled to a JS file. For example, a file called math_fns.re can be required by a JS file:

import { add } from './math_fns.re'

const sum = add(1, 4)

Reason Scripts will automatically configure a Jest environment to test Reason code. Any code found in a file ending with _test.re will be considered a test and run with Jest. From these files, the normal Jest API can be used interacting with any other modules defined in your app. For example:

/* math_fns.re */

let add x y => x + y;

/* math_fns_test.re */

open Jest;

test "addition" (fun () => {
  let num_1 = 10;
  let num_2 = 12;

  expect (Math_fns.add num_1 num_2) |> toBe 22;
});

For more documentation on the Jest API, see bs-jest

You can require CSS files with:

[%bs.raw {|require('./App.css')|}];

or any other kind of file (like SVG's) with:

let logo : string = [%bs.raw {|require('./logo.svg')|}];

Reason Scripts automatically generates an interface to any library installed with npm and FlowTyped

If you type the exports of a JS file with Flow types, you can use the file directly in Reason. For example, in the file math_fns.js:

// @flow
// math_fns.js

export function add(x: number, y: number): number {
  return x + y;
}

you will be able to access add in a Reason file with:

let run_func x y => Math_fns x y;