下面是我的代码，输出的结果是“P null 1 H5 null 1”，看不出啥错呀
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<div id="con"><p>javascript</p><div>jQuery</div><h5>PHP</h5></div>
<script type="text/javascript">
var x=document.getElementById("con");
document.write(x.firstChild.nodeName+" "+x.firstChild.nodeValue+" "+x.firstChild.nodeType+"<br />");
document.write(x.lastChild.nodeName+" "+x.lastChild.nodeValue+" "+x.lastChild.nodeType+"<br />");
</script>
</body>
</html>
