用js实现倒计时（js代码）

    <script language="javascript" type="text/javascript">
        var i = 5;
        var interval;
       interval= setInterval("fun()", 1000);
       function fun() {
           if (i == 0) {
               window.location.href = "http://www.cctv.com.cn";
               clearInterval(interval);
           }
            document.getElementById("mes").innerHTML = i;
            i--;
        }
   
    </script>