JavaScript实现窗口抖动效果详解

<!DOCTYPE HTML>
<html>
<head>
<meta charset="gb2312"/>
<title>窗口登陆效果</title>
<style type="text/css">
#win
{
 position:relative;
 width:100px;
 height:100px;
 background-color:#666;
}
</style>
<script type="text/javascript"> 
var a=['top','left'];
var b=0; 
var u;
function fudu()
{ 
 win.style[a[b%2]]=(b++)%4<2?"0px":"4px"; 
 if(b>15)
 {
  clearInterval(u);
  b=0
 } 
}
function zd()
{
 clearInterval(u); 
 u=setInterval(fudu,32) 
} 
window.onload=function()
{
 var bt=document.getElementById("bt");
 var win=document.getElementById("win");
 bt.onclick=zd;
}
</script> 
</head> 
<body > 
<button id="bt">点击振动</button> 
<div id="win"></div> 
</body> 
</html>