jsは無限ツリーナビゲーションリストエフェクトコード_javascriptスキルを実装します

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<style type="text/css"> 
 *{ margin:0; padding:0; list-style:none;} 
 body { margin:20px;} 
 h2 { font-family:"黑体"; font-size:24px; text-align:center; line-height:32px;} 
 h5 { font-size:12px; text-align:center; font-weight:normal; color:#666; line-height:28px;} 
 #nav a { text-decoration:underline;color:#06c; font-size:14px; line-height:24px;} 
 #nav ul{ margin-bottom:5px;} 
 #nav strong{ color:#696;} 
 #nav.dyn li ul{ display:none;} 
 #nav.dyn li ul.show{ display:block;} 
 #nav.dyn li{ padding-left:15px;} 
 #nav.dyn li.parent{ background:url(images/user_23.gif) 5px 10px no-repeat;} 
 #nav.dyn li.open{ background:url(images/user_23.gif) 5px -34px no-repeat;} 
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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>