<!DOCTYPE html>
<html>
<head>
<meta charset=" utf-8">
<meta name="author" content="http://www.51texiao.cn/" />
<title>蚂蚁部落</title>
<script type="text/javascript">
window.onload=function(){
var tags=document.getElementsByTagName("*"),
count=tags.length, time, ret = {}, id;
time=new Date();
for(var i = 0; i < count; i++)
{
id=tags[i].id;
if(id)
{
if(ret[id])
{
alert(id + "/n用时：" + (new Date() - time));
return;
}
else
{
ret[id]=true;
}
}
}
alert("未找到相同ID");
}
</script>
</head>
<body>
</body>
</html>原文：http://www.cnblogs.com/makan/p/4682114.html