看如下代码,为什么 要输入两个 setTimeout("startCount()",500)
<script type="text/javascript">
var num=0;
function startCount() {
document.getElementById('count').value=num;
num=num+1;
setTimeout("startCount()",500)
}
setTimeout("startCount()",500)
</script>
</head>
<body>
<form>
<input type="text" id="count" />
</form>
</body>