功能：显示时钟
<html>
<head>
<title>test</title>
</head>
<body onload="startTime();">
<div id="txt"></div>
</body>
</html>
<script type="text/javascript">
function startTime() {
var today = new Date()
var y = today.getFullYear();
var M = today.getMonth() + 1
var d = today.getDate();
var h = today.getHours()
var m = today.getMinutes()
var s = today.getSeconds()
// add a zero in front of numbers<10
m = checkTime(m)
s = checkTime(s)
document.getElementById('txt').innerHTML = y + "-" + M + "-" + d + " " + h + ":" + m + ":" + s;
t = setTimeout('startTime()', 500) //定时器，500ms执行递归一次
}
function checkTime(i) {
if (i < 10)
{ i = "0" + i }
return i
}
</script>