为什么没有显示倒计时，但是5秒以后会实现页面的跳转
<body>
<h3>操作完成</h3>
<p><span id="s">5</span>秒后将会跳转页面<a href="#" onclick="fanhui()">返回</a></p>
<script>
var e = document.getElementById("s").innerText;
var s = parseInt(e);
var intervalld;
intervalld = window.setInterval("showS()",1000);
function showS()
{
s--;
if(s<1)
{
window.clearInterval(intervalld);
window.location.href = "http://www.imooc.com";
}
e = s;
}
function fanhui(){
if(window.history.length>0)
{
window.history.go(1);
}
}
</script>
</body>
