<html>
<head>
<script type="text/javascript">
var c=0
var t
function timedCount()
{
document.getElementById('txt').value=c
c=c+1
t=setTimeout("timedCount()",1000)
}
function stopCount()
{
c=0;
setTimeout("document.getElementById('txt').value=0",0);
clearTimeout(t);
}
</script>
</head>
<body>
<form>
<input type="button" value="开始计时！" onClick="timedCount()">
<input type="text" id="txt">
<input type="button" value="停止计时！" onClick="stopCount()">
</form>
<p>请点击上面的“开始计时”按钮来启动计时器。输入框会一直进行计时，从 0 开始。点击“停止计时”按钮可以终止计时，并将计数重置为 0。</p>
</body>
</html>