JS格式化日期和格式化日期的字符串转日期

js把日期对象格式化为字符串：

//完整的格式化js方法  var time2 = new Date().format("yyyy-MM-dd HH:mm:ss");
//c#后台的格式化方法 now.Date.ToString("yyyy-MM-dd HH:mm:ss")

//完整的格式化  var time2 = new Date().format("yyyy-MM-dd HH:mm:ss");
Date.prototype.format = function (fmt) {
	var o = {
		"M+": this.getMonth() + 1, //月份
		"d+": this.getDate(), //日
		"h+": this.getHours(), //小时
		"m+": this.getMinutes(), //分
		"s+": this.getSeconds(), //秒
		"q+": Math.floor((this.getMonth() + 3) / 3), //季度
		"S": this.getMilliseconds() //毫秒
	};
	//处理年份
	var reYear = /(y+)/;
	var resultYear = reYear.exec(fmt);
	if (resultYear) {
		var yearformatPart = resultYear[0]; //匹配到的格式化字符
		var yearVal = (this.getFullYear() + "").substr(4 - yearformatPart.length);
		fmt = fmt.replace(yearformatPart, yearVal);
	}
	for (var k in o) {
		var re = new RegExp("(" + k + ")");
		var res = re.exec(fmt);
		if (res) {
			var Val = "" + o[k]; //本次需要替换的数据
			var formatPart = res[0]; //匹配到的格式化字符
			var replaceVal = (formatPart.length == 1) ? (Val) : (("00" + Val).substr(Val.length));
			fmt = fmt.replace(formatPart, replaceVal);
		}
	}
	return fmt;
}
Date.prototype.AddDays = function (days) {
	var olddays = this.getDate();
	var newdays = olddays + days;
	this.setDate(newdays);
	return this;
}

把上边格式化好的字符串转为日期对象：

/*获取到年月日，时分秒，毫秒几个值，然后生成日期
第一个参数为格式化的日期字符串，格式化的字符串
测试代码
var data=new Date();
var  format ="yyyy-MM-dd HH:mm:ss";
var text=data.format(format);
alert(text);
var data2=parserToDate(text,format);
alert(data2.format(format));
 */
function parserToDate(dateText, format) {
	if (!dateText) { //空值
		return new Date();
	}	
	//定义默认值，默认值根据当前时间生成
	var defaultVal = new Date();
	var year = defaultVal.getFullYear();
	var month = defaultVal.getMonth() + 1;
	var day = defaultVal.getDate();
	var hours = defaultVal.getHours();
	var minutes = defaultVal.getMinutes();
	var seconds = defaultVal.getSeconds();
	var milliseconds = defaultVal.getMilliseconds();
	//定义正则
	var o = [{
			reg: "y+"
		}, //年份
		{
			reg: "M+"
		}, //月份
		{
			reg: "d+"
		}, //日
		{
			reg: "H+"
		}, //小时
		{
			reg: "m+"
		}, //分
		{
			reg: "s+"
		}, //秒
		{
			reg: "S"
		} //毫秒
	];
	//获取到年月日，时分秒，毫秒几个值在字符串中的先后位置
	var index = 1;
	for (var j = 0; j < format.length; j++) {
		var onechar = format[j];
		for (var i = 0; i < o.length; i++) {
			var onepart = o[i]
				var onepartReg = onepart.reg;
			if (onepartReg[0] == onechar) {
				if (!onepart.index) {
					onepart.index = index; //获取到年月日，时分秒，毫秒几个值在字符串中的先后位置
					index++;
				}
				break;
			}
		}

	}
	//生成匹配的正则表达式
	for (var i = 0; i < o.length; i++) {
		var onepart = o[i]
			var onepartReg = onepart.reg;
		var re = new RegExp("(" + onepartReg + ")");
		var res = re.exec(format);
		if (res) {
			var formatPart = res[0]; //匹配到的格式化字符
			var replaceVal = "([0-9]{" + formatPart.length + "})"; //不能使用/d匹配,会和日期的d冲突
			format = format.replace(formatPart, replaceVal);
		}
	}
	//保存获取到的各个部分和位置
	var dataInfo = {};
	var re = new RegExp(format);
	var res = re.exec(dateText);
	//去掉第一个匹配，记录匹配到的数据
	if (res) {
		for (var i = 1; i < res.length; i++) {
			dataInfo[i] = res[i]; //记录年月日，时分秒，毫秒几个值在字符串中的位置和对应的值
		}
	} else {
		alert(dateText + "格式不匹配" + oldformat);
	}
	if (o[0].index) //年份存在
	{
		var index = o[0].index;
		year = dataInfo[index];
	}
	if (o[1].index) //月份存在
	{
		var index = o[1].index;
		month = dataInfo[index]; 
	}
	if (o[2].index) //日存在
	{
		var index = o[2].index;
		day = dataInfo[index];
	}
	if (o[3].index) //小时存在
	{
		var index = o[3].index;
		hours = dataInfo[index];
	}
	if (o[4].index) //分存在
	{
		var index = o[4].index;
		minutes = dataInfo[index];
	}
	if (o[5].index) //秒存在
	{
		var index = o[5].index;
		seconds = dataInfo[index];
	}
	if (o[6].index) //毫秒存在
	{
		var index = o[6].index;
		milliseconds = dataInfo[index];
	}
	//月份是从0开始的
	return new Date(year, month - 1, day, hours, minutes, seconds, milliseconds);
}

还有比上边更简单的方法，可惜IE不支持

/*获取到年月日，时分秒，毫秒几个值，然后生成日期
第一个参数为格式化的日期字符串，格式化的字符串
测试代码
var data=new Date();
var  format ="yyyy-MM-dd HH:mm:ss";
var text=data.format(format);
alert(text);
var data2=parserToDate(text,format);
alert(data2.format(format));
 */
function parserToDate(dateText, format) {
	if (!dateText) { //空值
		return new Date();
	}
  //定义默认值，默认值根据当前时间生成	
	var defaultVal = new Date();
	var year = defaultVal.getFullYear();
	var month = defaultVal.getMonth() + 1;
	var day = defaultVal.getDate();
	var hours = defaultVal.getHours();
	var minutes = defaultVal.getMinutes();
	var seconds = defaultVal.getSeconds();
	var milliseconds = defaultVal.getMilliseconds();

	//定义正则和对应的默认值，默认值根据当前时间生成
	var o = [{
			reg: "y+",
			regNew: "(?[0-9]{length})"
		}, //年份
		{
			reg: "M+",
			regNew: "(?[0-9]{length})"
		}, //月份
		{
			reg: "d+",
			regNew: "(?[0-9]{length})"
		}, //日
		{
			reg: "H+",
			regNew: "(?[0-9]{length})"
		}, //小时
		{
			reg: "m+",
			regNew: "(?[0-9]{length})"
		}, //分
		{
			reg: "s+",
			regNew: "(?[0-9]{length})"
		}, //秒
		{
			reg: "S",
			regNew: "(?[0-9]{length})"
		} //毫秒
	];
	//生成匹配的正则表达式
	for (var i = 0; i < o.length; i++) {
		var onepart = o[i]
			var onepartReg = onepart.reg;
		var re = new RegExp("(" + onepartReg + ")");
		var res = re.exec(format);
		if (res) {
			var formatPart = res[0]; //匹配到的格式化字符
			var regNew = onepart.regNew;
			var replaceVal = regNew.replace("length", formatPart.length);
			format = format.replace(formatPart, replaceVal);
		}
	}	
	var re = new RegExp(format);
	var res = re.exec(dateText);
	//去掉第一个匹配，记录匹配到的数据
	if (res.groups) {
		var A1 = res.groups["A1"];
		if (A1) {
			year = A1;
		}
		var A2 = res.groups["A2"];
		if (A2) {
			month = A2;
		}
		var A3 = res.groups["A3"];
		if (A3) {
			day = A3;
		}
		var A4 = res.groups["A4"];
		if (A4) {
			hours = A4;
		}
		var A5 = res.groups["A5"];
		if (A5) {
			minutes = A5;
		}
		var A6 = res.groups["A6"];
		if (A6) {
			seconds = A6;
		}
		var A7 = res.groups["A7"];
		if (A7) {
			milliseconds = A7;
		}
	} else {
		alert(dateText + "格式不匹配" + oldformat);
	}

	return new Date(year, month - 1, day, hours, minutes, seconds, milliseconds);
}