JavaScript实现自动切换图片代码

<!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>
<title> new document </title>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
<meta name="author" content="" />
<meta name="keywords" content="" />
<meta name="description" content="" />
<link rel="stylesheet" type="text/css" href="" />
<style type="text/css"></style>
<script type="text/javascript">
window.onload=init;
var n=1; //图片标记数
var dingshi; //让图片动的定时器
function init(){
dingshi=window.setInterval("tupian()",1000);
}
//更换图片
function tupian(){
var obj=document.getElementById("img1");
n++;
if(n>=4){
n=1;
}
obj.src="yaj_"+n+".jpg";
}
//鼠标放上图片停止
function stoptupian(){
window.clearInterval(dingshi);
}
//鼠标离开图片动起来
function dongqilai(){
dingshi=window.setInterval("tupian()",1000);
}
</script>
</head>
<body>
<img src="yaj_1.jpg" onmouseover="stoptupian()" onmouseout="dongqilai()" id="img1"> 
</body>
</html>