README

JS with Reason Scripts

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

JS with Reason Scripts provides a JS entrypoint into a react app, with the ability to use Reason where you like while building your React app. 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, and Reason from JS code.

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 js-with-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 create-react-app
$ create-react-app <app-name> --scripts-version js-with-reason-scripts
$ cd <app-name>
$ npm start

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.js
    index.css
    App.js
    hello_reason.re
    hello_reason_test.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

Unlike Reason Scripts, the entry point to the app is src/index.js. From the start your new app will be based on Javascript, but can seamlessly include ReasonML 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;

/* 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);
});

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')|}];

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

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

Help, Tips, and Tricks

My app won't compile on a fresh install

Try running npm install in your project directory. This helps refresh missing dependencies sometimes.

My editor isn't autocompleting

Editor support is provided by Merlin. To generate a .merlin file, run the app with npm start or yarn start.

See our full editor integration guide here: https://reasonml.github.io/docs/en/editor-plugins.html

I don't want js-with-reason-scripts to clear my terminal

Use FORCE_COLOR=true react-scripts start | cat - as your start command instead

Reason is awesome! Where can I learn more?

Checkout our fancy website: https://reasonml.github.io/!

Usage no npm install needed!