获取某个时间开始 之后的 N次[周几,周几]

废话不多说，直接上菜！

                        //PS :这里需要注意的是 周日 是 0 ！！！！！

                        console.log(getBeforeDate(-10000)) //一万天之后的日期

			console.log(getWeek('2019-07-03',[2,3],20))//从'2019-07-03' 开始获取之后 20 个 周二、周三的日期

/**

 * 获取某个时间开始 之后的 N次[周几,周几]

 * @param {Object} begin 开始时间

 * @param {Object} week_arr 需要获取的周几数组

 * @param {Object} Max 需要获取数组最大长度

 */

 function getWeek (begin, week_arr,Max){

     var dateArr = new Array();

     var stimeArr = begin.split("-");//=>["2018", "01", "01"]

     var etimeArr = getBeforeDate(-10000).split("-");//=>["2018", "01", "30"] 这里我给了一个10000天后的一起可更具需求更改

     var stoday = new Date();

     stoday.setUTCFullYear(stimeArr[0], stimeArr[1]-1, stimeArr[2]);

     var etoday = new Date();

     etoday.setUTCFullYear(etimeArr[0], etimeArr[1]-1, etimeArr[2]);

     var unixDb = stoday.getTime();//开始时间的毫秒数

     var unixDe = etoday.getTime();//结束时间的毫秒数

     for (var k = unixDb; k <= unixDe;) {

     	//达到最大次数时,结束循环

     	if(dateArr.length==Max){

     		break;

     	}else{

     		let needJudgeDate = msToDate(parseInt(k)).withoutTime;

	        //不加这个if判断直接push的话就是已知时间段内的所有日期

	        $.each(week_arr, function(i,o) {

	        	if (new Date(needJudgeDate).getDay() === o) {

		            dateArr.push(needJudgeDate);

		        }

	        })

	         k = k + 24*60*60*1000;

     	}

     }

     return dateArr;

 }

//根据毫秒数获取日期

function msToDate (msec) {

    let datetime = new Date(msec);

    let year = datetime.getFullYear();

    let month = datetime.getMonth();

    let date = datetime.getDate();

    let hour = datetime.getHours();

    let minute = datetime.getMinutes();

    let second = datetime.getSeconds();

    let result1 = year +

                 '-' +

                 ((month + 1) >= 10 ? (month + 1) : '0' + (month + 1)) +

                 '-' +

                 ((date + 1) < 10 ? '0' + date : date) +

                 ' ' +

                 ((hour + 1) < 10 ? '0' + hour : hour) +

                 ':' +

                 ((minute + 1) < 10 ? '0' + minute : minute) +

                 ':' +

                 ((second + 1) < 10 ? '0' + second : second);

    let result2 = year +

                 '-' +

                 ((month + 1) >= 10 ? (month + 1) : '0' + (month + 1)) +

                 '-' +

                 ((date + 1) < 11 ? '0' + date : date);

    let result = {

        hasTime: result1,

        withoutTime: result2

    };

    return result;

}

//-----[获取前n天的日期]

function getBeforeDate(n) {

	var n = n;

	var d = new Date();

	var year = d.getFullYear();

	var mon = d.getMonth() + 1;

	var day = d.getDate();

	if(day <= n) {

		if(mon > 1) {

			mon = mon - 1;

		} else {

			year = year - 1;

			mon = 12;

		}

	}

	d.setDate(d.getDate() - n);

	year = d.getFullYear();

	mon = d.getMonth() + 1;

	day = d.getDate();

	s = year + "-" + (mon < 10 ? ('0' + mon) : mon) + "-" + (day < 10 ? ('0' + day) : day);

	return s;

}

//-----[获取前n天的日期END]