JavaScript 背景时钟实现方法

<html>
<head>
<TITLE>背景时钟</TITLE> 
<script language=javaScript>
<!--// 
function clockon() {
thistime= new Date()
var hours=thistime.getHours()
var minutes=thistime.getMinutes()
var seconds=thistime.getSeconds()
if (eval(hours) <10) {hours="0"+hours}
if (eval(minutes) < 10) {minutes="0"+minutes}
if (seconds < 10) {seconds="0"+seconds}
thistime = hours+":"+minutes+":"+seconds
if(document.all) {
bgclocknoshade.innerHTML=thistime
bgclockshade.innerHTML=thistime
}
if(document.layers) {
document.bgclockshade.document.write('<div id="bgclockshade" style="position:absolute;visibility:visible;font-family:Verdana;color:FFAAAAA;font-size:120px;top:10px;left:152px">'+thistime+'</div>')
document.bgclocknoshade.document.write('<div id="bgclocknoshade" style="position:absolute;visibility:visible;font-family:Verdana;color:DDDDDD;font-size:120px;top:10px;left:150px">'+thistime+'</div>')
document.close()
}
var timer=setTimeout("clockon()",200)
}
//-->
</script>
<link rel="stylesheet" href="../style.css"></head>
<body onLoad="clockon()">
<div id="bgclockshade" style="position:absolute;visibility:visible;font-family:Arial;color:FF8888;font-size:120px;top:102px;left:152px"></div>
<div id="bgclocknoshade" style="position:absolute;visibility:visible;font-family:Arial;color:DDDDDD;font-size:120px;top:100px;left:150px"></div>
<div id="mainbody" style="position:absolute; visibility:visible">
</div>
</body>
</html>