js事件模型、代理及委托

1、事件的三个阶段：捕获、目标、冒泡（低版本的IE不支持捕获阶段）
2、传统、IE、W3C的绑定、解绑等事件略有不同
3、addEventListener()的第三个参数的值：false (冒泡执行) ， true (捕获执行)，默认为false

function Event(){
	this.addHander = function(ele,type,fn){
		if(document.addEventListener){//ie9、ff、sa、op、ch
			ele.addEventListener(type,fn,false)
		}else if(document.attachEvent){//ie、op
			ele.attachEvent('on'+type,fn)
		}else{//传统
			ele['on'+type] = fn;
		}
	}
  	this.delHander = function(ele,type,fn){
		if(document.removeEventListener){
			ele.removeEventListener(type,fn,false)
		}else if(document.detachEvent){
			ele.detachEvent('on'+type,fn)
		}else{
			ele['on'+type] = null;
		}
	}
	this.getEvent = function(event){
		return event ? event:window.event;
	}
	this.getTarget = function(event){
		return event.target || event.srcElement;
	}
	this.preventDefault = function(event){
		if(event.preventDefault){
			event.preventDefault();
		}else{
			event.returnValue = false;
		}
	}
	this.stopPropagation = function(event){
		if(event.stopPropagation){
			event.stopPropagation()
		}else{
			event.cancelBubble = false;
		}
	}
}