显示毫秒的时钟

[html]
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script type="text/javascript">

var t www.zzzyk.com
function timedCount()
{
startTime();
}

function startTime()
{
var today=new Date()
var h=today.getHours()
var m=today.getMinutes()
var s=today.getSeconds()
var ms=today.getMilliseconds()
// add a zero in front of numbers<10
m=checkTime(m)
s=checkTime(s)
ms=Math.floor(checkTime(ms)/100)
document.getElementById('txt').value=h+":"+m+":"+s+":"+ms
t=setTimeout('startTime()',100)
}

function checkTime(i)
{
if (i<10)
{i="0" + i}
return i
}

function stopCount()
{
clearTimeout(t)
}

function isKeyPressed(event)
{
if (event.ctrlKey==1)
    {

   startTime();
    }
if(event.shiftKey==1)
    {

   stopCount()
    }
}
</script>
</head>

<body onkeydown="isKeyPressed(event)">
<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。输入框会从 0 开始一直进行计时。点击"停止计时"可停止计时。
</p>

</body>

</html>

补充：web前端 , JavaScript ,