求助 !! 为什么这段是让c里面的内容都执行一次?length是怎么算的?for(a=0;a<c.length;a++)
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<ul id="con">
<li id="lesson1">javascript
<ul>
<li id="tcon"> 基础语法</li>
<li>流程控制语句</li>
<li>函数</li>
<li>事件</li>
<li>DOM</li>
</ul>
</li>
<li id="lesson2">das</li>
<li id="lesson3">dadf</li>
<li id="lesson4">HTML/CSS
<ul>
<li>文字</li>
<li>段落</li>
<li>表单</li>
<li>表格</li>
</ul>
</li></ul>
<script type="text/javascript">
var mylist = document.getElementById("tcon");
var p = mylist.parentNode.parentNode.parentNode;
var c = p.childrenNode;
for(a=0;a<c.length;a++) {
if(c[i].getAttribute("id").NodeType=="lesson4"){
var inner = c[i].childNode;
for(z=0;z<inner.length;z++) {
document.write(inner[z].innerHTML+" ");
}
}
}
</script>
</body>
</html>
