                        課程
                    
                        /前端開發(fā)
                        
                            /JavaScript
                        
                        /Tab選項卡切換效果

急，有木有大神幫忙看看我這個為什么隱藏的無法顯示

<!DOCTYPE?html>
<html>
<head>
<meta?charset="UTF-8">
<title>tab</title>
<style?type="text/css">
????*{margin:0;
?????padding:0;
?????font-size:13px;
?????list-style:none;}

.menu{width:210px;
??????margin:50px?auto;
??????border:1px?solid?#ccc;}

.menu?p{height:25px;
????????line-height:25px;
????????font-weight:bold;
????????background:#eee;
????????border-bottom:1px?solid?#ccc;
????????cursor:pointer;
????????padding-left:5px;}

.menu?div?ul{display:none;}

.menu?li{height:24px;
?????????line-height:24px;
?????????padding-left:5px;}
</style>
<script?type="text/javascript">
window.onload=function(){
??????//?將所有點擊的標題和要顯示隱藏的列表取出來
??????var?title=document.getElementsByTagName('p');
?var?ul=document.getElementsByTagName('ul');
?????//?遍歷所有要點擊的標題且給它們添加索引及綁定事件
??????if(title.length==ul.length){?????
???????for?(i?=?0;?i?<?title.length;?i++)?{??????
????????title[i].id=i;
???????title[i].onclick=function?()?{
?????//?獲取點擊的標題上的索引屬性，根據該索引找到對應的列表
???????if?(ul[this.id].style.display='block')?{
???????ul[this.id].style.display='none'
???????}else{?
????????????????ul[this.id].style.display='block'
???????}

??????};
}}
?????//?判斷該列表，如果是顯示的則將其隱藏，如果是隱藏的則將其顯示出來

}
</script>
</head>
<body>
<div?id="menu">
<div>
<p>Web前端</p>
<ul?style="display:block">
<li>JavaScript</li>
<li>DIV+CSS</li>
<li>jQuery</li>
</ul>
</div>
<div>
<p>后臺腳本</p>
<ul>
<li>PHP</li>
<li>ASP.net</li>
<li>JSP</li>
</ul>
</div>
<div>
<p>前端框架</p>
<ul>
<li>Extjs</li>
<li>Esspress</li>
<li>YUI</li>
</ul>
</div>
</div>
</body>
</html>