js实现带三角符的手风琴效果

效果图：

图（1）初始图

图（2）点击展开图

代码如下：

<!DOCTYPE html>
<html>
 <head>
 <meta charset="UTF-8">
 <title></title>
 <style>
  *{
  margin: 0;
  padding: 0;
  }
  li{
  list-style: none;
  }
  #list{
  width: 240px;
  border: 1px solid #666;
  margin: 20px auto;
  }
  #list .lis{
  }
  #list h2{
  height: 30px;
  line-height: 30px;
  overflow: hidden;
  background: lightsalmon;
  color: #f1f1f1;
  }
  #list h2.active{
  background: pink;
  height: 30px;
  line-height: 30px;
  overflow: hidden;
  color: #666;
  }
  #list h2.active div{
  display: inline-block;
  width: 0;
  height: 0;
  border-left: 8px solid transparent;
  border-top: 12px solid #666;
  border-right:8px solid transparent;
  border-bottom:2px solid transparent;
  margin-right: 4px;
  }
  #list h2 div{
  display: inline-block;
  width: 0;
  height: 0;
  border-left: 12px solid #f1f1f1;
  border-right: 6px solid transparent;
  border-bottom: 9px solid transparent;
  border-top:9px solid transparent;
  /*margin-right: 3px;*/
  }
  #list .lis ul{
  display: none;
  }
  #list .lis ul li{
  line-height: 24px;
  border-bottom: 1px solid #666;
  text-indent: 15px;
  }
  #list .lis ul li.hover{
  background: lightgreen;
  color: #F8F8F8;
  }
  #list .lis ul li:first-of-type{
  border-top: 1px solid #ccc;
  }
  #list .lis:last-of-type ul li:last-of-type{
  border-bottom:none;
  }
 </style>
 <script>
  window.onload=function(){
  var oUl=document.getElementById('list');
  var aH2=oUl.getElementsByTagName('h2');
  var aUl=oUl.getElementsByTagName('ul');
  var h2Len=aH2.length;
  var aLi=null;
  var arrLi=[];
  var aUlLen=aUl.length;
  for(var i=0;i<h2Len;i++){
   aH2[i].index=i;
   aH2[i].onclick=function(){
   if(this.className=='')
   {
    aUl[this.index].style.display='block';
    this.className='active';
   }
   else{
    aUl[this.index].style.display='none';
    this.className='';
   }
   }
  }
  for(var i=0;i<aUlLen;i++){
   aLi=aUl[i].getElementsByTagName('li');
   for(var j=0;j<aLi.length;j++){
   arrLi.push(aLi[j]);
   }
  }
  for(var i=0;i<arrLi.length;i++){
   arrLi[i].onclick=function(){
   for(var i=0;i<arrLi.length;i++){
    arrLi[i].className='';
   }
   this.className='hover';
   }
  }
  }
 </script>
 </head>
 <body>
 <ul id="list">
  <li class="lis">
  <h2><div></div>大学同学</h2>
  <ul>
   <li>张三</li>
   <li>张三</li>
   <li>张三</li>
   <li>张三</li>
  </ul>
  </li>
  <li class="lis">
  <h2><div></div>高中同学</h2>
  <ul>
   <li>李四</li>
   <li>李四</li>
   <li>李四</li>
   <li>李四</li>
  </ul>
  </li>
  <li class="lis">
  <h2><div></div>初中同学</h2>
  <ul>
   <li>王五</li>
   <li>王五</li>
   <li>王五</li>
   <li>王五</li>
  </ul>
  </li>
 </ul>
 </body>
</html>

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