一个倒计时的小程序，模拟了leftPad函数

<div id="divTimeRemains">xxxx</div>

<script language="JavaScript" type="text/javascript">
String.prototype.leftPad = function(n, s) {
	s = s || " ";
	if (this.length < n) {
		var ts = new Array(n - 1);
		ts[n - 1] = this;
		for (var i = 0; i < n - this.length; i++) {
			ts[i] = s;
		}
		return ts.join("");
	} else {
		return this;
	}
}

Date.prototype.format = function(style) {
	var o = {
		"M+" : this.getMonth() + 1, //month
		"d+" : this.getDate(),      //day
		"h+" : this.getHours(),     //hour
		"m+" : this.getMinutes(),   //minute
		"s+" : this.getSeconds(),   //second
		"w+" : "\u65e5\u4e00\u4e8c\u4e09\u56db\u4e94\u516d".charAt(this.getDay()),   //week
		"q+" : Math.floor((this.getMonth() + 3) / 3),  //quarter
		"S"  : this.getMilliseconds() //millisecond
	}
	if (/(y+)/.test(style)) {
		style = style.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
	}
	for(var k in o){
		if (new RegExp("("+ k +")").test(style)){
			style = style.replace(RegExp.$1, RegExp.$1.length == 1 ? o[k] : ("00" + o[k]).substr(("" + o[k]).length));
		}
	}
	return style;
};

//script's begin...
var timeEnd = new Date(2012, 3, 27, 9, 0, 0);

function showRemainsTime(){
	var timeNow = new Date();
	var timeRemains = timeEnd - timeNow;

	var rs = [];
	rs[rs.length] = "距离";
	rs[rs.length] = timeEnd.format("yyyy年MM月dd日h时m分s秒还有：");
	rs[rs.length] = Math.floor(timeRemains/(1000 * 60 * 60 * 24));
	rs[rs.length] = "天";
	rs[rs.length] = (Math.floor(timeRemains/(1000 * 60 * 60)) % 24).toString().leftPad(2, "0");
	rs[rs.length] = "小时";
	rs[rs.length] = (Math.floor(timeRemains/(1000 * 60)) % 60).toString().leftPad(2, "0");
	rs[rs.length] = "分";
	rs[rs.length] = (Math.floor(timeRemains/1000) % 60).toString().leftPad(2, "0");
	rs[rs.length] = "秒";

	document.getElementById("divTimeRemains").innerHTML = rs.join("");
	setTimeout("showRemainsTime()",1000);
}
showRemainsTime();
//script's end...
</script>

原文链接： http://blog.csdn.net/kimsoft/article/details/6783836