The new JS class syntax is no panacea as it is implied in the video. I mean, there are other ways to fix this: https://youtu.be/05Z6YGiZKmE?t=11m42s

infile.js

'use strict'

/*!
 * exports.
 */

module.exports = initialize

/*!
 * object initialization.
 */

function initialize () {
  return Object.assign({ files: { minified: [] } })
}

jsfile.js

'use strict'

/*!
 * imports.
 */

const infile = require('./infile')

/*!
 * exports.
 */

module.exports = initialize

/*!
 * object initialization.
 */

function initialize () {
  return Object.assign(infile(), { addJavaScript })
}

/*!
 * Add JavaScript file.
 */

function addJavaScript (data, sourceMap, path) {
  this.files.minified.push({ data, sourceMap, path })
}

You may prefer it terse:

module.exports = function initialize () {
  return Object.assign(infile(), {
    addJavaScript (data, sourceMap, path) {
      this.files.minified.push({ data, sourceMap, path })
    }
  })
}

You may also like ES6 class:

export class JsFile extends InputFile {
  addJavaScript({ data, sourceMap, path }) {
    this._minifiedFiles.push({ data, sourceMap, path })
  }
}

Just keep in mind, ES6 class is not necessary the correct tool for everything.

If I want to follow the "composition over inheritance" principle, should I do this ?

var compose = Object.assign.bind(Object, {})

module.exports = compose(InputFile, {
  addJavaScript({ data, sourceMap, path }) {
    this._minifiedFiles.push({ data, sourceMap, path })
  }
})

I don't think Meteor can handle this

@sylvainpolletvillard

Looks good to me. The only thing to be aware of is if you are supporting older browsers (IE 8/9) you may want to pull in a replacement for Object.assign and Object.create since those have spotty or no support for ES5 features. I don't like using big shim libraries but rather like to replace just the functions I know are problematic.

For more info on this concept, check out: https://github.com/wilmoore/polykata/tree/master/oloo-game-player-poc/js