JavaScript+CSS多级树形展开菜单的代码，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。
演示：
<!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>JavaScript+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(/uploads/allimg/1209/treeico.gif) -4px -31px no-repeat;}#root .ren{background:url(/uploads/allimg/1209/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;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]);elselabels[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;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]);elsethis.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><div style="text-align:center;margin:30px 0 0 0;"><hr style="color:#999;height:1px;">如不能显示效果，请按Ctrl+F5刷新本页，更多网页代码：<a href='http://www.wfuyu.com/' target='_blank'>http://www.wfuyu.com/</a></div>提示：可修改后代码再运行!
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