運行結果： 前一個節點出不來
<!DOCTYPE?html>
<html?lang="en">
<head>
????<meta?charset="UTF-8">
????<title>兄弟節點</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;
????}
????function?get_previousSibling(n)?{
????????var?a=n.previousSibling;
????????while(a&&a.nodeType!=1){
????????????a=a.previousSibling;
????????}
????????return?b;
????}
????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+"<br??/><br??/>");
????}else{
????????document.write("<br>已經是最后一個節點"+"<br?/><br??/>");
????}
????var?a=document.getElementsByTagName("li")[2];
????document.write("</br>"+a.nodeName);
????document.write("=");
????document.write(a.innerHTML);
????var?b=get_previousSibling(a);
????if(b!=null){
????????document.write("</br>previousSibling");
????????document.write(b.nodeName);
????????document.write("=");
????????document.write(b.innerHTML+"</br>")
????}else{
????????document.write("這是第一個節點")
????}
</script>
</body>
</html>運行結果： ?前一個節點出不來
javascript
jquery
html
css3
php
java
LI = javascript
nextSibling: LI = jquery
LI=html這是第一個節點
2019-09-18
function?get_previousSibling(n)?{ ????????var?a=n.previousSibling; ????????while(a&&a.nodeType!=1){ ????????????a=a.previousSibling; ????????} ????????return?b; ????}你的這個函數里沒有b這個變量，你return b干嘛，改成a試一下咯