<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
</head>
<body>
<span id="timeout">0</span>秒后返回首页
<script type="text/javascript">
var timestart = 30;
var timestep = -1;
var timeID;
function timecount() {
document.getElementById("timeout").innerHTML = timestart;
timestart += timestep;
if(timestart < 0){
alert(12)
timestart = 30;
//倒计时为0时执行xxxx方法
}
timeID=setTimeout("timecount()",1000);
}
timecount()
</script>
</body>
</html>
