<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>自动跳转首页</title>
<style>
 p{
	text-align : center;
 }
 
 span{
	color:red;
 }
</style>
</head>
<body>
    <p>
        <span id="time">5</span>秒之后,自动跳转首页...
    </p>

<script>
    //获取倒计时秒数
    var time = document.getElementById("time");
    var second = 5;
    function showTime(){
		second -- ;
        if(second <= 0){
            //时间到了，跳转首页
            location.href = "https://www.baidu.com";
        }
        time.innerHTML = second;
    }
    setInterval(showTime,1000);
</script>
</body>
</html>