//---------------------------------------------------
// 判断闰年
//---------------------------------------------------
Date.prototype.isLeapYear = function()
{
	return (0==this.getYear()%4&&((this.getYear()%100!=0)||(this.getYear()%400==0)));
};

//---------------------------------------------------
// 日期格式化
// 格式 YYYY/yyyy/YY/yy 表示年份
// MM/M 月份
// W/w 星期
// dd/DD/d/D 日期
// hh/HH/h/H 时间
// mm/m 分钟
// ss/SS/s/S 秒
//---------------------------------------------------

Date.prototype.Format = function(formatStr)
{
	var str = formatStr;
	var Week = ['日','一','二','三','四','五','六'];
	str=str.replace(/yyyy|YYYY/,this.getFullYear());
	str=str.replace(/yy|YY/,(this.getYear() % 100)>9?(this.getYear() % 100).toString():'0' + (this.getYear() % 100));
	str=str.replace(/MM/,(this.getMonth() + 1)>9?(this.getMonth() + 1).toString():'0' + (this.getMonth() + 1));
	str=str.replace(/M/g,this.getMonth() + 1);
	str=str.replace(/w|W/g,Week[this.getDay()]);
	str=str.replace(/dd|DD/,this.getDate()>9?this.getDate().toString():'0' + this.getDate());
	str=str.replace(/d|D/g,this.getDate());
	str=str.replace(/hh|HH/,this.getHours()>9?this.getHours().toString():'0' + this.getHours());
	str=str.replace(/h|H/g,this.getHours());
	str=str.replace(/mm/,this.getMinutes()>9?this.getMinutes().toString():'0' + this.getMinutes());
	str=str.replace(/m/g,this.getMinutes());
	str=str.replace(/ss|SS/,this.getSeconds()>9?this.getSeconds().toString():'0' + this.getSeconds());
	str=str.replace(/s|S/g,this.getSeconds());
	return str;
};

//+---------------------------------------------------
//| 求两个时间的天数差 日期格式为 YYYY-MM-dd
//+---------------------------------------------------
function daysBetween(DateOne,DateTwo)
{
	var OneMonth = DateOne.substring(5,DateOne.lastIndexOf('-'));
	var OneDay = DateOne.substring(DateOne.length,DateOne.lastIndexOf('-')+1);
	var OneYear = DateOne.substring(0,DateOne.indexOf('-'));
	var TwoMonth = DateTwo.substring(5,DateTwo.lastIndexOf('-'));
	var TwoDay = DateTwo.substring(DateTwo.length,DateTwo.lastIndexOf('-')+1);
	var TwoYear = DateTwo.substring(0,DateTwo.indexOf('-'));
	var cha=((Date.parse(OneMonth+'/'+OneDay+'/'+OneYear)- Date.parse(TwoMonth+'/'+TwoDay+'/'+TwoYear))/86400000);
	return Math.abs(cha);
}

//+---------------------------------------------------
//| 日期计算
//+---------------------------------------------------
Date.prototype.DateAdd = function(strInterval, number) {
	var dtTmp = this;
	switch (strInterval) {
	case 's' :return new Date(Date.parse(dtTmp.toGMTString()) + (1000 * number));
	case 'n' :return new Date(Date.parse(dtTmp.toGMTString()) + (60000 * number));
	case 'h' :return new Date(Date.parse(dtTmp.toGMTString()) + (3600000 * number));
	case 'd' :return new Date(Date.parse(dtTmp.toGMTString()) + (86400000 * number));
	case 'w' :return new Date(Date.parse(dtTmp.toGMTString()) + ((86400000 * 7) * number));
	//FIXME 以下两种对跨年的增加有异常
//	case 'q' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number*3, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());
//	case 'm' :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());
	case 'y' :return new Date((dtTmp.getFullYear() + number), dtTmp.getMonth(), dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());
	}
};

//+---------------------------------------------------
//| 比较日期差 dtEnd 格式为日期型或者 有效日期格式字符串
//+---------------------------------------------------
Date.prototype.DateDiff = function(strInterval, dtEnd) {
	var dtStart = this;
	if (typeof dtEnd == 'string' )//如果是字符串转换为日期型
	{
	dtEnd = StringToDate(dtEnd);
	}
	switch (strInterval) {
	case 's' :return parseInt((dtEnd - dtStart) / 1000);
	case 'n' :return parseInt((dtEnd - dtStart) / 60000);
	case 'h' :return parseInt((dtEnd - dtStart) / 3600000);
	case 'd' :return parseInt((dtEnd - dtStart) / 86400000);
	case 'w' :return parseInt((dtEnd - dtStart) / (86400000 * 7));
	case 'm' :return (dtEnd.getMonth()+1)+((dtEnd.getFullYear()-dtStart.getFullYear())*12) - (dtStart.getMonth()+1);
	case 'y' :return dtEnd.getFullYear() - dtStart.getFullYear();
	}
};

//+---------------------------------------------------
//| 日期输出字符串，重载了系统的toString方法
//+---------------------------------------------------
Date.prototype.toString = function(showWeek)
{
	var myDate= this;
	var str = myDate.toLocaleDateString();
	if (showWeek)
	{
	var Week = ['日','一','二','三','四','五','六'];
	str += ' 星期' + Week[myDate.getDay()];
	}
	return str;
};

2.调用格式

//格式化日期
var date=new Date();
var res=date.Format("yyyy-MM-dd HH:mm:ss  星期W");
console.info(res);
var date1=new  Date();
//增加2个星期
var date2=date1.DateAdd('w',2);
//求日期差
var dif=daysBetween(date1.Format("yyyy-MM-dd"),date2.Format("yyyy-MM-dd"))
console.info(dif);
//比较日期差
var dateDiff=date1.DateDiff('d',date2);
console.info(dateDiff);
//toString
console.info(date1.toString())
//判断是否是闰年
console.info(date1.isLeapYear())

3.结果

2014-10-08 10:13:25  星期三
14
13
2014/10/8
false