                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /JavaScript進階篇

無法輸出y.nodeName怎么回事

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>nextSibling</title>
</head>
<body>
<ul id="u1">??
??????????? <li id="a">javascript</li>??
??????????? <li id="b">jquery</li>??
??????????? <li id="c">html</li>??
??????? </ul>??
??????? <ul id="u2">??
??????????? <li id="d">css3</li>??
??????????? <li id="e">php</li>??
??????????? <li id="f">java</li>??
??????? </ul>??
<script type="text/javascript">
??? function getnext(n){
??????? var x=n.nextSibling;
??????? while(x && x.nodeType!=1)
??????? {
??????????? x=x.nextSibling;
??????? }
??????????? return x;
??? }
??? var x=document.getElementsByTagName("li")[0];
??????? document.write(x.nodeName+"="+x.innerHTML+"<br/");
??? var y=getnext(x);
??? if(y!=null){
??????? document.write(y.nodeName+"="+y.innerHTML);
?????? }
???? else{
??????? document.write("已經是最后一個節點")
???? }
</script>
</body>
</html>