JS n秒后自动跳转实例

<p><a href="<?php echo base_url();?>usercenter/index" id="message"></a> </p> 

<script type="text/javascript">
var time = 0;
var forward_url ="<?php echo base_url();?>usercenter/index";//某页网址
function forward_to(){
     time ++;
     if(time == 5){
         document.location.href = forward_url;
     }
     document.getElementById("message").innerHTML = (5-time) + "秒后自动跳转到某页";
}
window.setInterval("forward_to()",1000);

</script>