How do I use ES6 (ES2015) in a ruby on rails app?

Question

I have a 4.2 rails app and am considering slowly converting the JS to ES6. Right now I\'m using the standard rails manifest file from the asset pipeline to pre-process my js

Answer 1

Answering for myself 3 years later...

Rails > 5.1 has webpacker and native support for webpack builds and various front end frameworks if desired (react, vue, etc)