本例是應用別人的例子，原來那位老兄是用一般方法寫成的無限級折疊菜單，在此先感謝他！后來我就通過了一些簡化修改，將原來的例子改成了面向對象的方式，實例中的展開與閉合的小圖標可以自己重新添加，從而更好的查看效果。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>很實用的JS+CSS多級樹形展開菜單</title> <style type="text/css"> body{margin:0;padding:0;font:12px/1.5 Tahoma,Helvetica,Arial,sans-serif;} ul,li,{margin:0;padding:0;} ul{list-style:none;} a{text-decoration: none;} #root{margin:10px;width:200px;overflow:hidden;} #root li{line-height:25px;} #root .rem{padding-left:16px;} #root .add{background:url(treeico.gif) -4px -31px no-repeat;} #root .ren{background:url(treeico.gif) -4px -7px no-repeat;} #root li a{color:#666666;padding-left:5px;outline:none;blr:expression(this.onFocus=this.blur());} #root .two{padding-left:20px;display:none;} </style> </head> <body> <ul id="root"> <li> <label><a href="javascript:;">校訊通</a></label> <ul class="two"> <li> <label><a href="javascript:;">沈陽市</a></label> <ul class="two"> <li> <label><a href="javascript:;">二小</a></label> <ul class="two"> <li><label><a href="javascript:;">二年級</a></label></li> <li> <label><a href="javascript:;">三年級</a></label> <ul class="two"> <li> <label><a href="javascript:;">一班</a></label> <ul class="two"> <li><label><a href="javascript:;">張三</a></label></li> <li> <label><a href="javascript:;">王五</a></label> <ul class="two"> <li><label><a href="javascript:;">班長</a></label></li> <li><label><a href="javascript:;">學習委員</a></label></li> </ul> </li> </ul> </li> <li><label><a href="javascript:;">實驗班</a></label></li> </ul> </li> </ul> </li> </ul> </li> <li> <label><a href="javascript:;">撫順市</a></label> <ul class="two"> <li><label><a href="javascript:;">二小</a></label></li> <li><label><a href="javascript:;">一中</a></label></li> </ul> </li> </ul> </li> </ul> <script type="text/javascript" > /**一般JS方法 function addEvent(el,name,fn){//綁定事件 if(el.addEventListener) return el.addEventListener(name,fn,false); return el.attachEvent('on'+name,fn); } function nextnode(node){//尋找下一個兄弟並剔除空的文本節點 if(!node)return ; if(node.nodeType == 1) return node; if(node.nextSibling) return nextnode(node.nextSibling); } function prevnode(node){//尋找上一個兄弟並剔除空的文本節點 if(!node)return ; if(node.nodeType == 1) return node; if(node.previousSibling) return prevnode(node.previousSibling); } addEvent(document.getElementById('root'),'click',function(e){//綁定點擊事件，使用root根元素代理 e = e||window.event; var target = e.target||e.srcElement; var tp = nextnode(target.parentNode.nextSibling); switch(target.nodeName){ case 'A'://點擊A標簽展開和收縮樹形目錄，並改變其樣式 if(tp&&tp.nodeName == 'UL'){ if(tp.style.display != 'block' ){ tp.style.display = 'block'; prevnode(target.parentNode.previousSibling).className = 'ren' }else{ tp.style.display = 'none'; prevnode(target.parentNode.previousSibling).className = 'add' } } break; case 'SPAN'://點擊圖標只展開或者收縮 var ap = nextnode(nextnode(target.nextSibling).nextSibling); if(ap.style.display != 'block' ){ ap.style.display = 'block'; target.className = 'ren' }else{ ap.style.display = 'none'; target.className = 'add' } break; } }); window.onload = function(){//頁面加載時給有孩子結點的元素動態添加圖標 var labels = document.getElementById('root').getElementsByTagName('label'); for(var i=0;i<labels.length;i++){ var span = document.createElement('span'); span.style.cssText ='display:inline-block;height:18px;vertical-align:middle;width:16px;cursor:pointer;'; span.innerHTML = ' ' span.className = 'add'; if(nextnode(labels[i].nextSibling)&&nextnode(labels[i].nextSibling).nodeName == 'UL') labels[i].parentNode.insertBefore(span,labels[i]); else labels[i].className = 'rem' } } **/ //面向對象方法 var Tree = function(o){ this.root = document.getElementById(o); this.labels = this.root.getElementsByTagName('label'); var that = this; this.int(); Tree.prototype.addEvent(this.root,'click',function(e){that.treeshow(e)}); } Tree.prototype = { int:function(){//初始化頁面，加載時給有孩子結點的元素動態添加圖標 for(var i=0;i<this.labels.length;i++){ var span = document.createElement('span'); span.style.cssText ='display:inline-block;height:18px;vertical-align:middle;width:16px;cursor:pointer;'; span.innerHTML = ' ' span.className = 'add'; if(this.nextnode(this.labels[i].nextSibling)&&this.nextnode(this.labels[i].nextSibling).nodeName == 'UL') this.labels[i].parentNode.insertBefore(span,this.labels[i]); else this.labels[i].className = 'rem' } }, treeshow:function(e){ e = e||window.event; var target = e.target||e.srcElement; var tp = this.nextnode(target.parentNode.nextSibling); switch(target.nodeName){ case 'A'://點擊A標簽展開和收縮樹形目錄，並改變其樣式 if(tp&&tp.nodeName == 'UL'){ if(tp.style.display != 'block' ){ tp.style.display = 'block'; this.prevnode(target.parentNode.previousSibling).className = 'ren' }else{ tp.style.display = 'none'; this.prevnode(target.parentNode.previousSibling).className = 'add' } } break; case 'SPAN'://點擊圖標只展開或者收縮 var ap = this.nextnode(this.nextnode(target.nextSibling).nextSibling); if(ap.style.display != 'block' ){ ap.style.display = 'block'; target.className = 'ren' }else{ ap.style.display = 'none'; target.className = 'add' } break; } }, addEvent:function(el,name,fn){//綁定事件 if(el.addEventListener) return el.addEventListener(name,fn,false); return el.attachEvent('on'+name,fn); }, nextnode:function(node){//尋找下一個兄弟並剔除空的文本節點 if(!node)return ; if(node.nodeType == 1) return node; if(node.nextSibling) return this.nextnode(node.nextSibling); }, prevnode:function(node){//尋找上一個兄弟並剔除空的文本節點 if(!node)return ; if(node.nodeType == 1) return node; if(node.previousSibling) return prevnode(node.previousSibling); } } tree = new Tree("root");//實例化應用 </script> </body> </html>