为什么停止不了啊？求大神帮忙看看原因！
<script type="text/javascript">
function clock(){
var time=new Date();
document.getElementById("clock").value = time;
}
var id = setInterval(clock,100);
</script>
</head>
<body>
<form>
<input type="text" id="clock" size="50" />
<input type="button" value="Stop" onclick="clearInterval(id)"/>
</form>
</body>
