<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()
{
clearTimeout(t)
}
function cs()
{
c=0
document.getElementById('txt').value= 0
}
</script>
</head>
<body>
<form>
<input type="button" value="开始!" id="start" onClick="timedCount()">
<input type="text" id="txt">
<input type="button" value="停止!" id="end" onClick="stopCount()">
<input type="button" value="清零！" id="ss" onClick="cs()">
</form>
</body>
</html>
