大家重點(diǎn)看一下JS語(yǔ)句。報(bào)錯(cuò)是Uncaught TypeError: Cannot read property 'style' of undefined。但是我要是用onclick來(lái)觸發(fā)確是可以得，好奇怪?。?lt;!doctype?html>
<html>
<head>
????<meta?charset="UTF-8">
<title>Document</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(){
var?menu?=?document.getElementById('menu'),
????????ps?=menu.getElementsByTagName('p'),
????????uls?=?menu.getElementsByTagName('ul');
????????
??????//?將所有點(diǎn)擊的標(biāo)題和要顯示隱藏的列表取出來(lái)
????????for(i=0;i<ps.length;i++){
????????var?u=uls[this.id];
??????????ps[i].onmouseover=?function(){
????????if?(u.style.display?==?'block')?{
u.style.display='none';
}
}
????????ps[i].onmouseout=?function()?{
????????if?(u.style.display?==?'none')?{
u.style.display='block';
}
}
}
}
</script>
</head>
<body>
<div?id="menu">
<div>
<p?id="0">Web前端</p>
<ul?style="display:block">
<li>JavaScript</li>
<li>DIV+CSS</li>
<li>jQuery</li>
</ul>
</div>
<div>
<p?id="1">后臺(tái)腳本</p>
<ul>
<li>PHP</li>
<li>ASP.net</li>
<li>JSP</li>
</ul>
</div>
<div>
<p?id="2">前端框架</p>
<ul>
<li>Extjs</li>
<li>Esspress</li>
<li>YUI</li>
</ul>
</div>
</div>
</body>
</html>
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