Reason Scripts

  $ 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.

Getting Started

Using Yarn

Note that using yarn create requires Yarn 0.25 or later

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

Make sure to install bs-platform globally using npm instead of yarn.

Using npm

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

(npx comes with npm 5.2+ and higher, see instructions for older npm versions)

The policy of reason tooling is to support the current LTS release, so please make sure you have Node 8 or later.

Directory Layout

Creating a new app makes an <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

Features

Everything from Create React App

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

Reason Entrypoint

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!

Automatic Compilation of Reason/OCaml files

Any Reason/OCaml 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)

Jest Integration

Reason Scripts will automatically configure a Jest environment to test Reason code. Any code found in a file ending with _test.re, _test.ml or test.js 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;

let add x y = x + y

/* math_fns_test.re */

open Jest;

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

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

964: syntax error, consider adding a `;' before

Or if you prefer writing your tests in JavaScript, just don't forget to import the tested module:

/* maths_fns.test.js */

import Math_fns from './math_fns.re'

test('addition', () => {
  const num1 = 10
  const num2 = 12

  expect(Math_fns.add(num1, num2)).toBe(22)
})

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

Importing non-Reason files

You can require CSS files with:

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

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

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

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

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

Help, Tips, and Tricks