js控制5秒返回指定界面，或上一个界面

js控制5秒返回指定界面，代码如下

<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<script type="text/javascript">
function countDown(secs,surl){
 //alert(surl);
 var jumpTo = document.getElementById('jumpTo');
 jumpTo.innerHTML=secs;
 if(--secs>0){
     setTimeout("countDown("+secs+",'"+surl+"')",1000);
     }
 else{
     location.href=surl;
     }
 }
</script>
</head>

<body><span id="jumpTo">5</span>秒后自动跳转到http://www.baidu.com/
<script type="text/javascript">countDown(5,'http://www.baidu.com/');</script>
</body>
</html>

5秒返回上一个界面，代码如下：

<!DOCTYPE html>

<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>没有权限</title>
@Styles.Render("~/Content/bootstrap3/css")
@Scripts.Render("~/s/jqbs")
</head>
<body>
<div>
<p style="text-align:center;margin-top:200px;font-size:larger;">
<img src="~/Content/images/404.png" />
Sorry！您没有访问该页面的权限！<span id="jumpTo">5</span>秒后返回上一个页面。
<button type="button" class="btn btn-primary"onclick="up()">返回上一个页面</button>
</p>

</div>
</body>

</html>
<script type="text/javascript">
countDown(5);
function up() {
window.history.back();
}
function countDown(secs) {
var jumpTo = document.getElementById('jumpTo');
jumpTo.innerHTML = secs;
if (--secs > 0) {
setTimeout("countDown(" + secs + ")", 1000);
}
else {
window.history.back();
}
}
</script>