                        課程
                    
                        /前端開發(fā)
                        
                            /JavaScript
                        
                        /DOM事件探秘

我的代碼哪里的問題

<!DOCTYPE?html>
<html>
<head?lang="en">
????<meta?charset="UTF-8">
????<title>事件流</title>
</head>
<body>
??<div?id="box">

??????<input?type="button"?value="按鈕"?id="btn"?onclick="show()">
??????<input?type="button"?value="按鈕2"?id="btn2"?>
??????<input?type="button"?value="按鈕3"?id="btn3"?>
??</div>
<script>
????//使用Html事件處理程序
?function?show()
????{
????????alert("hello");
????}

????//使用DOM0級事件處理程序
?function?show2(){
????????alert("使用DOM0級事件處理程序");
????????alert(this.value);
????}
????/*var?b2;
????b2?=?document.getElementById("btn2");
????b2.onclick=show2();

????//使用DOM2級事件處理程序??第一個參數(shù)中開頭的ON?去掉
????var?b3;
????b3?=?document.getElementById("btn3");

????b3.addEventListener('click',show2,false);*/

???/*?b2?=?document.getElementById("btn2");
????//IE中添加DOM2級事件處理程序
????b2.attachEvent('onclick',show2);
????b2.detachEvent('onclick',show2);*/
?var?EventUtil=?{
????????addHandler:?function?(element,?type,?handler)?{
????????????if?(element.addEventListener())?{
????????????????element.addEventListener(type,?handler,?false);

????????????}?else?if?(element.attachEvent())?{
????????????????element.attachEvent('on'?+?type,?handler);

????????????}?else?{
????????????????element['on'?+?type]?=?handler;
????????????}
????????},
????????//刪除句柄
?deleteHandler:?function?(element,?type,?handler)?{
????????????if?(element.removeEventListener())?{
????????????????element.removeEventListener(type,?handler,?false);

????????????}?else?if?(element.detachEvent())?{
????????????????element.detachEvent('on'?+?type,?handler);

????????????}?else?{
????????????????element['on'?+?type]?=?null;
????????????}
????????}
????}
????var?btn3=document.getElementById("btn3");
????EventUtil.addEventListener(btn3,'click',show2());
</script>
</body>
</html>