使用js实现倒数和跳转页面

<scripttype="text/javascript">
var i = 5;
var intervalid;
intervalid = setInterval("count_down()", 1000);

function count_down()
{
if (i == 0)
{
window.location.href = "http://www.google.com";
clearInterval(intervalid);
}
document.getElementByIdx_x("show_sec_div").innerHTML = i;
i--;
}
</script>
<divid='show_sec_div'></div>