<html><head>
<script type="text/javascript">
var num=0;
var t;function start()
{
document.getElementById('123').value=num;
num++;
t=setTimeout("start()",1000);
}function paste()
{
clearTimeout(t);
}
</script>
</head><body>
<input type="button" value="单击开始" onclick="start()" />
<input type="text" id=123 />
<input type="button" value="单击结束" onclick="paste()" />
</body></html>
http://msdn.microsoft.com/en-us/library/ms536782%28VS.85%29.aspx
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=gb2312"/>
<script type="text/javascript">
var num=0;
var t;
function starts()
{
document.getElementById('123').value=num;
num++;
t=setTimeout("starts()",1000);
}
function paste()
{
clearTimeout(t);
}
</script>
</head>
<body>
<input type="button" value="单击开始" onclick="starts()" />
<input type="text" id=123 />
<input type="button" value="单击结束" onclick="paste()" />
</body>
</html>