http://blog.csdn.net/yzy0612/archive/2007/08/07/1730732.aspx 

<html> 
<head>
<title> test </title> 
<script language="javascript">   
	
	function test() {
		var testDate = new Date();
		alert(testDate);
		var testStr = testDate.format("yyyy-MM-dd hh:mm:ss");
		alert(testStr);
	}

	Date.prototype.format = function(format){
		var o = {
				"M+" :  this.getMonth()+1,  //month
				"d+" :  this.getDate(),     //day
				"h+" :  this.getHours(),    //hour
				"m+" :  this.getMinutes(),  //minute
				"s+" :  this.getSeconds(), //second
				"q+" :  Math.floor((this.getMonth()+3)/3),  //quarter
				"S"  :  this.getMilliseconds() //millisecond
			}
			if(/(y+)/.test(format)) {
				format = format.replace(RegExp.$1, (this.getFullYear()+"").substr(4 - RegExp.$1.length));
			}
			for(var k in o) {
				if(new RegExp("("+ k +")").test(format)) {
					format = format.replace(RegExp.$1, RegExp.$1.length==1 ? o[k] : ("00"+ o[k]).substr((""+ o[k]).length));
				}
			}
		return format;
	}
</script> 
</head> 
<body>   
<a href="#">test</a>
</body> 
</html>