无法执行执行clearTimeout？
代码如下，无法执行clearTimeout，通过console.log()可以看到startCount()一直在运行，请问为什么？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>计时器</title>
</head>
</head>
<body>
<form>
<input type="text" id="count" />
</form>
<script type="text/javascript">
var num=0,i;
function startCount() {
console.log(num);
if(num==5){
stopCount();
}
document.getElementById('count').value=num;
num=num+1;
i=setTimeout("startCount()",1000);
}
function stopCount(){
clearTimeout(i);
}
startCount()
</script>
</body>
</html>
