JavaScript实现防刷新倒计时与定时任务实例

<!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=gb2312" />
<title>前端开发</title>
</head>
<body>
<SCRIPT LANGUAGE="JavaScript">
var maxtime;
if(window.name=='' || window.name == '-1' || isNaN(window.name)){
maxtime = 1*60;
}else{
maxtime = window.name;
}
function CountDown(){
if(maxtime>=0){
hours = Math.floor(maxtime/3600);
minutes = Math.floor((maxtime-hours*3600)/60);
seconds = Math.floor(maxtime%60);
msg = "距离考试结束还有"+hours+"时"+minutes+"分"+seconds+"秒";
document.all["timer"].innerHTML = msg;
if(maxtime == 5*60) alert('注意，还有5分钟!');
--maxtime;
window.name = maxtime;
}
else{
clearInterval(timer);
alert("考试时间到，结束!");
}
}
timer = setInterval("CountDown()",1000);
</SCRIPT>
<div id="timer" style="color:red"></div>
</body>
</html>

//后台查询执行请求 1min , ajax_wx_payment 为方法名
setInterval(ajax_wx_payment,1000*60);

//延迟跳转 20min
setTimeout('ys_time_out()', 1000*60*20);