为什么我的代码实现不了点击切换的功能，求指点
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html"; charset="UTF-8" />
<title>taobao demo</title>
<style type="text/css">
@font-face{font-family: iconfont;src:url(http://g.tbcdn.cn/tb/icon-font/1.1.5/iconfont.eot);}
src: url(http://g.tbcdn.cn/tb/icon-font/1.1.5/iconfont.eot?#iefix) format("embedded-opentype"),
url(http://g.tbcdn.cn/tb/icon-font/1.1.5/iconfont.woff) format("woff"),
url(http://g.tbcdn.cn/tb/icon-font/1.1.5/iconfont.tff) format("truetype"),
url(http://g.tbcdn.cn/tb/icon-font/1.1.5/iconfont.svg#uxiconfont) format("svg");
}
body{font-size: 12px/1.5 tahoma,arial,sans-serif; }
a{text-decoration: none;}
.search-tips{float: right;padding: 3px 0 0 15px;}
.search-tips{color: #6c6c6c;}
.search-button{float: right;}
.btn-search{background-color: #F90;color:#FFF;width: 100px;height: 45px;border: 0;cursor: pointer;font-size: 18px;}
.search-common-panel{height: 39px;background-color: #f50;overflow: hidden;padding: 3px 0 3px 77px;}
.search-common-panel input{height: 37px;line-height: 37px;width: 100%;border: 0 none;outline: 0;background-color: #FFF;}
.iconfont{font-family: iconfont;font-size: 12px;font-style: normal;}
.search-container{position: relative;}
.search-common-panel i{position: absolute;top: 14px;left: 86px;z-index: 2;color: #ccc;}
ul{list-style: none;display: block;}
ul,li{margin: 0;padding: 0;}
.search-list{position: absolute;top:3px;left: 3px;width: 72px;height: 39px;overflow: hidden;background-color: #fff;border-left: 1px solid #f6f6f6;border-right: 1px solid #e5e5e5;text-align: center;}
.search-list li{display: none;height: 39px;line-height: 39px;overflow: hidden;}
.search-list li a{color: #6c6c6c;}
.search-list .selected{background: #f6f6f6;display: block;}
.trigger-hover{height: auto;}
.trigger-hover li{display: block;}
</style>
</head>
<body>
<div class="search-container">
<div id="search_tab" class="search-list">
<ul>
<li id="tab_1" class="selected "><a href="#">宝贝</a></li>
<li id="tab_2"><a href="#">店铺</a></li>
</ul>
</div>
<div class="pannel">
<form>
<div class="search-tips">
<a href="#">高级<br>搜索</a>
</div>
<div class="search-button">
<button class="btn-search" type="submit">搜 索</button>
</div>
<div class="search-common-panel">
<input type="text" name="" x-webkit-speech="">
<i class="iconfont">ő</i>
</div>
</form>
</div>
</div>
</body>
<script>
var getDOM = function (id) {
return document.getElementById(id);
}
var addEvent = function(id,event,fn){
var el = getDOM(id)||document;
if(el.addEventListener){
el.addEventListener(event,fn,false);
}else if(el.attachEvent){
el.attachEvent('on'+event,fn);
}
}
addEvent('search_tab','mouseover',function () {
this.className+=' trigger-hover';});
addEvent('tab_1','mouseover',function () {
if(this.className.indexOf('selected')<0){
this.className+=' selected';}
});
addEvent('tab_1','mouseout',function () {
this.className='';
});
addEvent('tab_1','click',function () {
getDOM('search_tab').className='search-list';
});
addEvent('tab_2','mouseover',function () {
if(this.className.indexOf('selected')<0){
this.className+=' selected';}
});
addEvent('tab_2','mouseout',function () {
this.className='';
});
addEvent('tab_2','click',function () {
getDOM('search_tab').className='search-list';
});
</script>
</html>
