JavaScript Event Target// source http://jsbin.com/kipame

jsbin.kipame.js

var EventTarget = function() {
  Object.defineProperty(this, "__listeners", {
    value: {}
  });
};

Object.defineProperties(EventTarget.prototype, {
  addListener: {
    value: function(type, listener) {
      if (typeof this.__listeners[type] === "undefined") {
        this.__listeners[type] = [];
      }

      this.__listeners[type].push(listener);
    },
    enumerable: true
  },
  __fire: {
    value: function(evtObj) {
      if (typeof evtObj.type === "undefined") {
        throw new Error("Event object needs type");
      }

      if (typeof evtObj.target === "undefined") {
        evtObj.target = this;
      }

      var listeners = this.__listeners[evtObj.type];

      if (typeof listeners === "undefined") {
        return;
      }

      for (var i = 0, len = listeners.length; i < len; i++) {
        listeners[i].call(this, evtObj);
      }
    }
  },
  removeListener: {
    value: function(type, listener) {
      var listeners = this.__listeners[type];

      if (typeof listeners == "undefined") {
        return;
      }

      for (var i = 0, len = listeners.length; i < len; i++) {
        if (listeners[i] === listener) {
          listeners.splice(i, 1);
          break;
        }
      }
    },
    enumerable: true
  }
});