EventEmitter.js

var EventEmitter = (function(){
  var EventEmitter = function(){
    this.listeners = {};
  };
  EventEmitter.prototype.emit = function(eventName){
    var args = Array.prototype.slice.apply(arguments, [1]);
    console.log(args);
    if (this.listeners[eventName]){
      for (var i = 0; i < this.listeners[eventName].length; i++){
        this.listeners[eventName][i].apply(this, args);
      }
    }
  };
  EventEmitter.prototype.on = function(eventName, callback){
    if (typeof this.listeners[eventName] === 'undefined'){
      this.listeners[eventName] = [];
    }
    this.listeners[eventName].push(callback);
  };
  return EventEmitter;
})();