使用js实现倒数和跳转页面

<script type="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>
 <div id='show_sec_div'></div>