明明有上一個節點的，結果卻是“已經是第一個節點了”
<!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?get_nextSibling(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);
????document.write("?=?");
????document.write(x.innerHTML);
????
????var?y=get_nextSibling(x);
????
????if(y!=null){
????????document.write("<br?/>nextsibling:?");
????????document.write(y.nodeName);
????????document.write("?=?");
????????document.write(y.innerHTML);
????}else{
??????document.write("<br>已經是最后一個節點");??????
????}
????
????//?獲取上一個節點代碼開始
????function?get_previousSibling(n){
????????var?x=n.previousSibling;
????????while?(x?&&?x.nodeType?!=?1){
????????????x=x.previousSibling;
????????}
????????return?x;
????}
????var?li5?=?document.getElementsByTagName("li")[4];
????document.write("<br/><br/>"?+?li5.nodeName);
????document.write("?=?");
????document.write(li5.innerHTML);
????var?node?=?get_previousSibling(a);
????if(node?!=?null){
????????document.write("<br/>previousSibling：");
????????document.write(node.nodeName);
????????document.write("?=?");
????????document.write(node.innerHTML);
????}else{
????????document.write("<br/>已經是第一個節點了");
????}
????
</script>
</body>
</html>為什么明明上一個節點是css的，結果卻是“已經是第一個節點了”？問題出在哪里？請大神指教
2014-12-25
為什么第7行要返回 li5啊
2014-12-06
暈，原來是自己傳參傳錯了，正確的代碼應該是這樣的：
//?獲取上一個節點代碼開始 ????function?get_previousSibling(n){ ????????var?li5=n.previousSibling; ????????while?(li5?&&?li5.nodeType?!=?1){ ????????????li5=li5.previousSibling; ????????} ????????return?li5; ????} ????var?li5?=?document.getElementsByTagName("li")[4]; ????document.write("<br/><br/>"?+?li5.nodeName); ????document.write("?=?"); ????document.write(li5.innerHTML); ????var?node?=?get_previousSibling(li5); ????if(node?!=?null){ ????????document.write("<br/>previousSibling："); ????????document.write(node.nodeName); ????????document.write("?=?"); ????????document.write(node.innerHTML); ????}else{ ????????document.write("<br/>已經是第一個節點了"); ????}