What is the best way to use ES6 with rails asset pipeline?. I am trying to write some es6 syntax in my angular-rails application, which uses the rails asset pipeline. The code actually works in local but throws a syntax error when trying to deploy(digital ocean). 
This is error I am getting while I am deploying. And the code I am trying to run is
class Hello {
constructor() {
alert('Hello!');
}
}
new Hello();