本例是应用别人的例子，原来那位老兄是用一般方法写成的无限级折叠菜单，在此先感谢他！后来我就通过了一些简化修改，将原来的例子改成了面向对象的方式，实例中的展开与闭合的小图标可以自己重新添加，从而更好的查看效果。
<!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>很实用的JS+CSS多级树形展开菜单</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:;">校讯通</a></label> <ul class="two"> <li> <label><a href="javascript:;">沈阳市</a></label> <ul class="two"> <li> <label><a href="javascript:;">二小</a></label> <ul class="two"> <li><label><a href="javascript:;">二年级</a></label></li> <li> <label><a href="javascript:;">三年级</a></label> <ul class="two"> <li> <label><a href="javascript:;">一班</a></label> <ul class="two"> <li><label><a href="javascript:;">张三</a></label></li> <li> <label><a href="javascript:;">王五</a></label> <ul class="two"> <li><label><a href="javascript:;">班长</a></label></li> <li><label><a href="javascript:;">学习委员</a></label></li> </ul> </li> </ul> </li> <li><label><a href="javascript:;">实验班</a></label></li> </ul> </li> </ul> </li> </ul> </li> <li> <label><a href="javascript:;">抚顺市</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){//绑定事件 if(el.addEventListener) return el.addEventListener(name,fn,false); return el.attachEvent('on'+name,fn); } function nextnode(node){//寻找下一个兄弟并剔除空的文本节点 if(!node)return ; if(node.nodeType == 1) return node; if(node.nextSibling) return nextnode(node.nextSibling); } function prevnode(node){//寻找上一个兄弟并剔除空的文本节点 if(!node)return ; if(node.nodeType == 1) return node; if(node.previousSibling) return prevnode(node.previousSibling); } addEvent(document.getElementById('root'),'click',function(e){//绑定点击事件，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'://点击A标签展开和收缩树形目录，并改变其样式 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'://点击图标只展开或者收缩 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(){//页面加载时给有孩子结点的元素动态添加图标 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;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' } } **/ //面向对象方法 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(){//初始化页面，加载时给有孩子结点的元素动态添加图标 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;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'://点击A标签展开和收缩树形目录，并改变其样式 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'://点击图标只展开或者收缩 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){//绑定事件 if(el.addEventListener) return el.addEventListener(name,fn,false); return el.attachEvent('on'+name,fn); }, nextnode:function(node){//寻找下一个兄弟并剔除空的文本节点 if(!node)return ; if(node.nodeType == 1) return node; if(node.nextSibling) return this.nextnode(node.nextSibling); }, prevnode:function(node){//寻找上一个兄弟并剔除空的文本节点 if(!node)return ; if(node.nodeType == 1) return node; if(node.previousSibling) return prevnode(node.previousSibling); } } tree = new Tree("root");//实例化应用 </script> </body> </html>