stefanpenner / esnext

Transform next-generation JavaScript to today's JavaScript.

esnext

Use tomorrow's JavaScript syntax today. Try it now in your browser.

Install

$ npm install [--save-dev] esnext

Goals

• Allow using future JavaScript syntax today.
• Require as little runtime code as possible.
• Generate human-readable code.

Non-Goals

• Provide polyfills for future JavaScript APIs.
• Line-by-line equivalence from source to compiled.

Features

Available

• arrow functions (via es6-arrow-function)
• classes (via es6-class)
• computed property keys (via [es6-computed-property-keys][es6-computed-property-keys])
• computed property keys (via es6-computed-properties)
• default params (via es6-default-params)
• destructuring (via es6-destructuring)
• generators (via regenerator)
• async-await (via regenerator)
• iterators + for-of (via regenerator)
• object literal concise definitions (via es6-object-concise)
• object literal shorthand (via es6-object-short)
• rest params (via es6-rest-params)
• spread (via es6-spread)
• template strings (via es6-templates)
• unicode regexes (via regexpu)

TODO

• block scoping (let)
• modules (i.e. integration with es6-module-transpiler)

Any omissions here are not intentional and we'd love to integrate support for more future JavaScript syntax (see es6features for a more complete list). See the Contributing section below. Keep in mind that, as of right now, this project is intended to support new JavaScript syntax only. Any new APIs should be handled using polyfills. This may change in the future.

Usage

As a CLI

esnext ships with a command-line interface that can be used when installed globally (or from within your project at node_modules/.bin/esnext when installed locally). Here's how to compile a single file an print it to stdout:

$ esnext myfile.js

If you don't care about a certain feature, such as arrow functions, you can omit support for them like so:

$ esnext --no-arrow-function myfile.js

To compile many files at once, specify an output directory:

$ esnext -o build lib/**/*.js

To enable source maps for these files, add the --source-maps flag.

As a Library

var compile = require('esnext').compile;
var result = compile(es6Source);
fs.writeFileSync('result.js', result.code, 'utf8');
fs.writeFileSync('result.js.map', JSON.stringify(result.map), 'utf8');

With other tools

esnext can be used out of the box as a Browserify transform (and can be used with watchify for better efficiency). For example:

$ browserify -t esnext main.js

Or, use one of these libraries that integrate esnext with other tools:

• broccoli-esnext
• grunt-esnext
• gulp-esnext
• esnext-loader

Contributing

Setup

First, install the development dependencies:

$ npm install

Then, try running the tests:

$ npm test

Pull Requests

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Any contributors to the master esnext repository must sign the Individual Contributor License Agreement (CLA). It's a short form that covers our bases and makes sure you're eligible to contribute.

When you have a change you'd like to see in the master repository, send a pull request. Before we merge your request, we'll make sure you're in the list of people who have signed a CLA.

Acknowledgements

Huge thanks to Ben Newman for recast and regenerator. Thanks to Ariya Hidayat for esprima. Thanks also to Thomas Boyt for his work on the es6-module-transpiler, es6-class, es6-arrow-function, and others.