jquery实现下拉菜单的手风琴效果

<div class="site-nav">  <ul class="site-accordion">    <li>      <div class="tab-head">学科领域</div>      <ul class="tabs-list">        <li>机械电子</li>        <li>生物工程</li>        <li>能源环保</li>        <li>化学化工</li>      </ul>    </li>    <li>      <div class="tab-head">省份地区</div>      <ul class="tabs-list">        <li>陕西省</li>        <li>江苏省</li>        <li>山东省</li>        <li>河南省</li>      </ul>    </li>    <li>      <div class="tab-head">经费范围</div>      <ul class="tabs-list">        <li>50万~100万</li>        <li>100万~200万</li>        <li>200万~500万</li>        <li>500万以上</li>      </ul>    </li>    <li>      <div class="tab-head">需求状态</div>      <ul class="tabs-list">        <li>状态1</li>        <li>状态2</li>      </ul>    </li>  </ul></div>

.site-accordion>li{  margin-top: 13px;}.site-accordion>li .tab-head{  width: 160px;  height: 40px;  line-height: 40px;  text-align: center;  color: #9c9c9c;  font-size: 16px;  background: #f2f2f2;}.site-accordion>li .tab-head:hover{  background: #292d48;}.site-accordion>li .tab-head:after{  content: '';  border: 5px solid #4F5160;  border-color: #4F5160 transparent transparent transparent;  margin-top: 20px;  position: relative;  top: 10px;  left: 5px;}.site-accordion>li .tabs-list{  display: none;}.site-accordion>li .tabs-list li{  width: 160px;  height: 40px;  line-height: 40px;  text-align: center;  color: #9c9c9c;.site-accordion>li .tabs-list li:hover{  background: #f2f2f2;} 

$('.tab-head').click(function(){          $(this).next().slideToggle();          $('.tab-head').css('background','#FFFFFF');          $(this).css('background','#292d48');        })