js实现无限级树形导航列表效果代码

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<h2>js实现无限级树形导航列表</h2>
<ul id="nav"> 
 <li><a href="#">主页</a></li> 
 <li><a href="#">产品</a> 
 <ul> 
  <li><a href="#">大类别一</a> 
  <ul> 
   <li><a href="#">小类别一</a> 
   <ul> 
    <li><a href="#">次类别一</a></li> 
    <li><a href="#">次类别二</a></li> 
   </ul> 
   </li> 
   <li><a href="#">小类别二</a></li> 
  </ul> 
  </li> 
  <li><a href="#">大类别二</a></li> 
  <li><a href="#">大类别三</a> 
  <ul> 
   <li><a href="#">小类别一</a></li> 
   <li><a href="#">小类别二</a></li> 
  </ul> 
  </li> 
 </ul> 
 </li> 
 <li><a href="#">服务</a> 
 <ul> 
  <li><a href="#">大类别一</a></li> 
  <li><a href="#">大类别二</a></li> 
  <li><a href="#">大类别三</a></li> 
 </ul> 
 </li> 
 <li><a href="#">合作</a></li> 
 <li><a href="#">关于我们</a> 
 <ul> 
  <li><a href="#">大类别一</a> 
  <ul> 
   <li><a href="#">小类别一</a></li> 
   <li><a href="#">小类别二</a></li> 
  </ul> 
  </li> 
  <li><a href="#">大类别二</a> 
  <ul> 
   <li><a href="#">小类别一</a></li> 
   <li><a href="#">小类别二</a></li> 
  </ul> 
  </li> 
  <li><a href="#">大类别三</a> 
  <ul> 
   <li><a href="#">小类别一</a></li> 
   <li><a href="#">小类别二</a></li> 
  </ul> 
  </li> 
  <li><a href="#">大类别四</a></li> 
 </ul> 
 </li> 
 <li><a href="#">联系我们</a> 
 <ul> 
  <li><a href="#">大类别一</a></li> 
  <li><a href="#">大类别二</a></li> 
 </ul> 
 </li> 
</ul>