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 createrequires 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;
/* 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
Try running npm install in your project directory. This helps refresh missing dependencies sometimes.
If this still does not work, make sure your file path does not include any spaces.
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
Use FORCE_COLOR=true react-scripts start, cat - as your start command instead
Checkout our fancy website: https://reasonml.github.io/!
We also have a very active Discord to come talk about Reason, and ask for help: https://discordapp.com/invite/reasonml