es6-extending-singleton-fail.js

let EventDispatcher = (function() {
  let instance = null;

  class EventDispatcher {
    constructor() {
      if(!instance) {
        instance = this;
      }

      return instance;
    }
  }

  return EventDispatcher;
}());

class Keyboard extends EventDispatcher {
  constructor() {
    super();
  }
}

class PlayerController extends Keyboard {
  constructor() {
    super();
  }
}

class PlayerModel extends EventDispatcher {
  constructor() {
    super();
  }
}

var playerModel = new PlayerModel();
var playerCtrl = new PlayerController();

console.log('instanceof playerCtrl', playerCtrl); // incorrect/overwritten instance