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Transpile ES6 Modules in the Rails Asset Pipeline

Uses Square's ES6 Module Transpiler


Node.js must be installed for the transpiling to happen

gem 'es6_module_transpiler-rails'


Your modules will transpile and are named based upon their directory nesting + filename, as long as the file has the .es6 extension. For example, app/assets/javascripts/controllers/fooController.js.es6

var fooController = function() {
  console.log('fooController is in the house!');

export default fooController;

will compile to /assets/controllers/fooController.js

  function(__exports__) {
    "use strict";
    var fooController = function() {
      console.log('fooController is in the house!');

    __exports__["default"] = fooController;


By default your module will compile to an AMD. You can also compile it to globals or CommonJS by making the following switch:

ES6ModuleTranspiler.compile_to = :globals
# or
ES6ModuleTranspiler.compile_to = :cjs

You may modify the options that are passed to the module compiler (i.e. compatFix) by modifying the compiler_options hash:

ES6ModuleTranspiler.compiler_options[:compatFix] = true;

The compiler_options hash is empty by default.

Loading Modules

When compiling to AMD or CommonJS, you'll need to be able to load the compiled result. In the below example, we're using a minimal AMD loader called loader.js. Without a loader, you'll get an error like:

Uncaught ReferenceError: define is not defined

For example, in application.js:

//= require loader
//= require_tree ./modules
//= require main


Now main.js.es6 is our entry point - from this file we can use the es6 module syntax to load any es6 modules in the ./modules directory.

Custom Module Prefix

You can match module names based upon a pattern to apply a prefix to the name. You can add multiple patterns (which can each have separate prefixes):

ES6ModuleTranspiler.add_prefix_pattern, 'app')), 'app'
ES6ModuleTranspiler.add_prefix_pattern, 'config')), 'config'

This would match names that start with the pattern and prepend with app/ or config/. For example, /home/user/app/controllers/fooController would now be named app/controllers/fooController, and /home/user/config/router would now be named config/router.

Note the path is made up of the root path and the logical path for the asset. For example, if the path to your asset is /home/user/app/assets/javascripts/controllers/fooController.js.es6 the root path is /home/user/app/assets/javascripts/ and the logical path is controllers/fooController. It is entirely dependent upon what Sprockets considers to be the mount point for the asset.


Brian Cardarella

We are very thankful for the many contributors


This gem follows Semantic Versioning

Want to help?

Please do! We are always looking to improve this gem.


DockYard, LLC © 2013


Licensed under the MIT license


Transpile ES6 Modules in the Rails Asset Pipeline




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