function EventDispatcher(){}

/**
EventDispatcher.initialize( obj )

オブジェクトobjに、W3C DOM3互換のイベント通知機能を追加します。
これによりobjは、onLoad等のイベントを発行することができます。
オブジェクトobjはこれにより、以下のプロパティと関数を装備します。
obj.addEventListener( イベント名, リスナーオブジェ);
obj.removeEventListener(　イベント名, リスナーオブジェクト);
obj.dispatchEvent( Eventオブジェクト);

@param obj オブジェクト
*/

EventDispatcher.initialize = function(obj){
//MIX IN following property and function int obj
//be careful about Name Scape Corrision just for incase
obj.__ed_eventContainer = new Object();
obj.addEventListener = this._addEventListener;
obj.removeEventListener = this._removeEventListener;
obj.dispatchEvent = this._dispatchEvent;
}

/*
CAUTION INTERNAL OBJECT do not call it directory from EventDispatcher
refered from targetObject.addEventListener()
*/

EventDispatcher._addEventListener = function(eventName, object){
//CAUTION
//third param is not implemented yet

//CAUTION:
//scope of this object is always "TARGET" OBJECT, not EventDispatcher
if( this.__ed_eventContainer[eventName]==null){
this.__ed_eventContainer[eventName]=new Array();
}
this.removeEventListener(eventName, object);
this.__ed_eventContainer[eventName].push(object); //register object
}

/*
CAUTION INTERNAL OBJECT do not call it directory from EventDispatcher

refered from targetObject.removeEventListener()
*/

EventDispatcher._removeEventListener = function(eventName, object){
//CAUTION:
//scope of this object is always "TARGET" OBJECT, not EventDispatcher
var listener_ar = this.__ed_eventContainer[eventName];
if(listener_ar == undefined) return;

var imax = listener_ar.length;
for(var i=0; i var listener = listener_ar[i];
if(listener==object){
listener_ar.splice(i,1);
return;
}
}
}

/*
CAUTION INTERNAL OBJECT do not call it directory from EventDispatcher
refered from targetObject.dispatchEvent()
*/

EventDispatcher._dispatchEvent = function(eventObj){
//CAUTION:
//scope of this object is always "TARGET" OBJECT,not EventDispatcher
if(eventObj.target==null) eventObj.target = this;

var eventName = eventObj.type;
if( this.__ed_eventContainer[eventName]==null) return;

var imax = this.__ed_eventContainer[eventName].length;
for(var i=0; i var listener = this.__ed_eventContainer[eventName][i];
if(typeof(listener)=="object"){
listener[eventName].apply(listener, new Array(eventObj));
return;
}else{
listener(eventObj);
return;
}
}
}

EventDispatcher.initialize(hogeObject)

//hogeオブジェクト
function hoge(){
//hogeインスタンスに、イベント通知機能を実装
EventDispatcher.initialize(this);
}

hoge.prototype.doSomething = function(){
//doSomethingを実行したらイベントを通知
this.dispatchEvent({type:"onSomething", target:this});
}

var h = new hoge(); // イベント機能つきhogeインスタンス作成。

var listener = new Object();
//イベントハンドラ
listener.onSomething = function(e){
alert("event受信 " + e.type);
}

h.addEventListener("onSomething", listener);

h.doSomething(); //doSomething実行のラストでイベントが発行される。