JS——覆盖显示，点击显示三层

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
*
{
    margin:0px;
    padding:0px;
    }

.all
{
    width:310px;
    height:50px;
    border:#03F 1px solid;
    }
.left
{
    width:250px;
    height:50px;
    border:#F00 1px solid;
    }
.right
{
    width:50px;
    height:50px;
    border:#0F3 1px solid;
    background-color:#CCC;
    margin-left:255px;
    }    
.yincang
{
    height:200px;
    width:200px;
    border:#30F 1px solid;
    background-color:#06F;
    margin-top:30px;
    visibility:hidden;

    }                            
</style>
</head>

<body>
<div class="all"> 
   <div class="left">
     <div class="right" onmouseover="xianshi()" onmouseout="yincang()">>><div class="yincang"  id="right"></div>
     </div>
        
   </div>

</div>

</body>
</html>
<script type="text/javascript">
function xianshi()
{
    var a =document.getElementById("right");
    
    if(a.style.visibility="hidden")
    {
        a.style.visibility="visible";
    }

    }
function yincang()
{
    var b =document.getElementById("right");
    
    if(b.style.visibility="visible")
    {
        b.style.visibility="hidden";
        
        }
    
    
    }

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
*
{
    margin:0px;
    padding:0px;
    }
.diyiceng
{
    width:500px;
    height:300px; 
    border:#9C6 1px solid; 
    margin:-300px 0px 0px 100px; 
    background-color:yellow;
    visibility:visible;
    }
.dierceng
{
    width:500px;
    height:300px; 
    border:#9C6 1px solid;
    background-color:green;
    visibility:hidden;
    margin-left:100px;
    }
.disanceng
{
    width:500px;
    height:300px; 
    border:#9C6 1px solid;
    margin-top:-300px;
    margin-left:200px;
    background-color:blue;
    visibility:hidden;
    }                
</style>
</head>

<body>
<div style="600px; height:300px; border:#00F 1px solid">
<div style="100px; height:300px; border:#F00 1px solid">
<input type="button" value="第一层"  onclick="xianshiyi()"/><br />
<input type="button" value="第二层"  onclick="xianshier()"/><br />
<input type="button" value="第三层"  onclick="xianshisan()"/>


</div>
  <!--第一层为黄色 第二层为绿色 第三层为蓝色-->
     <div class="diyiceng" id="diyiceng">
         <div class="dierceng" id="dierceng"></div>
              <div class="disanceng" id="disanceng"></div>

     </div>


</div>

</body>
</html>
<script type="text/javascript">
function xianshiyi()
  {
       var a = document.getElementById("dierceng");
       var b = document.getElementById("disanceng");
       var c = document.getElementById("diyiceng");
       
       if(c.style.visibility="hidden")
       {
           c.style.visibility="visible";
           a.style.visibility="hidden";
           b.style.visibility="hidden";
           
           }
      
      
      }      
  function xianshier()
  {
      var a = document.getElementById("dierceng");
      var b = document.getElementById("disanceng");
       if(a.style.visibility="hidden")
       {
           
           a.style.visibility="visible";
           b.style.visibility="hidden";
           }
  }
  function xianshisan()
  {
         var b=document.getElementById("disanceng");
         if(b.style.visibility="hidden")
        {
             b.style.visibility="visible";
        }
                 
  }
      
  
    


</script>

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原文地址：https://www.cnblogs.com/Chenshuai7/p/5252994.html