This app demostrate how to use Yarn as package manager for Rails assets and using ES6 as default javascript engine.
In new apps the support for Yarn will be added using the --yarn option:
rails new todo --yarn
This install the dependencies defined by default in package.json for new apps, right now this include jquery and jquery-ujs
Also is possible to install the dependencies defined in package.json in an existing app:
yarn
To add new dependencies just use yarn add command:
yarn add angular
You can add a specify version of dependencies in the command:
yarn add angular@^1.5.8
To delete an unused dependency use the yarn remove command:
yarn remove jquery-ujs
The dependencies installed by Yarn can be used in Sprockets as long as they work exporting browser globals (most of the dependencies for browsers do this already), if you want to use CommonJS/AMD dependencies you need to have a CommonJS/AMD environment for Sprockets or a bundler like Webpack or Browserify.
For more info about Yarn read the Getting Started guide.
Support for Babel is added with the babel-rails gem, underneath this just add the babel-transpiler gem as dependency to the project, set babel as default javascript engine and add generators for ES2015 (.es6 files).
Sprockets detects that babel-transpiler is included as dependency and register the Babel processor for .es6 files.
By default Babel transpiles ES2015 modules to CommonJS modules hence you will need a CommonJS environment for Sprockets or a bundler like Webpack or Browserify if you want to use ES2015 modules.
Check Babel docs to get more info about ES2015.