//加够了后利用这个停止
//window.clearInterval(k)
<html><head>
<title>reduce</title>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
$(function (){
reduceTime()
})
function reduceTime() {
var reduce = $("#tt").html()
if(reduce == 0){
return
}else{
$("#tt").html(--reduce)
setTimeout(reduceTime,1000)
}
}
</script>
</head>
<body>
<span id="tt">6</span>
</body>
</html>