倒计时跳转

Question

页面上显示：还有3秒中页面跳转...
3是按照时间变化的3 2 1 0 到0的时候页面跳转到一个指定的页面，
比如a.jsp
这个功能如何实现

Answer 1

    页面没有找到 <span id="time"></span>后自动跳转动主页    <script language="javascript" type="text/javascript">
(function()
{
        var count = 3;
        var time = document.getElementById("time");
        var timer;
        time.innerHTML = count
        function lessTime()
        {
                time.innerHTML = --count;
                if(!count)
                {
                        window.clearInterval(timer);
                        window.location.href = "../Index.aspx";
                }
        }
        timer = window.setInterval(lessTime,1000);
})()
    </script>

Answer 2

<span id="counter"></span>
<script type="text/javascript">
var t = 3;
function countDown() {
document.getElementById('counter').innerHTML = t;
t --;
if (t <= 0) window.location = 'a.jsp';
else setTimeout('countDown()',1000);
}
countDown();
</script>