为什么用document.getElementsByTagName()获取的元素节点不能用呢？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>节点属性</title>
</head>
<body>
<ul id="tt">
<li>javascript</li>
</ul>
<script type="text/javascript">
var lii = document.getElementsByTagName("li");
document.write(lii.nodeName+"<br/>");
document.write(lii.nodeValue+"<br/>");
document.write(lii.nodeType+"<br/>");
</script>
</body>
</html>
