js获取选中日期的当周的周一和周日

js获取选中日期的当周的周一和周日

第一种方法（推荐）：

 　　function getWeekStr(str) {
         // 将字符串转为标准时间格式
         str2 = Date.parse(str);
         let date = new Date(str2);
         let month = date.getMonth() + 1;
         let week = getWeekFromDate(date);
         if (week === 0) {//第0周归于上月的最后一周
             month = date.getMonth();
             let dateLast = new Date();
             let dayLast = new Date(dateLast.getFullYear(), dateLast.getMonth(), 0).getDate();
             let timestamp = new Date(new Date().getFullYear(), new Date().getMonth() - 1, dayLast);
             week = getWeekFromDate(new Date(timestamp));
         }
         let time = month + "月第" + week + "周";
         return time;
     }

     function getWeekFromDate(date) {
         // 将字符串转为标准时间格式
         let w = date.getDay();//周几
         if (w === 0) {
             w = 7;
         }
         let week = Math.ceil((date.getDate() + 6 - w) / 7) - 1;
         return week;
     }

     console.log("2018-02-3---" + getWeekStr("2018-02-3"));
     console.log("2018-02-4---" + getWeekStr("2018-02-4"));
     console.log("2018-02-5---" + getWeekStr("2018-02-5"));
     console.log("2018-02-12---" + getWeekStr("2018-02-12"));
     console.log("2018-02-19---" + getWeekStr("2018-02-19"));
     console.log("2018-02-28---" + getWeekStr("2018-02-28"));
     console.log("2018-03-1---" + getWeekStr("2018-03-1"));
     console.log("2018-03-5---" + getWeekStr("2018-11-1"));
     console.log("2018-08-27---" + getWeekStr("2018-12-01"));

第二种方法（比较复杂）：　　

 console.log(getNowDateAndNowWeek(1539187200000));

     /**
      * 获取当月的第几周
      * a = d = 当前日期
      * b = 6 - w = 当前周的还有几天过完(不算今天)
      * a + b 的和在除以7 就是当天是当前月份的第几周
     */
     function getMonthWeek(a, b, c) {

         var date = new Date(a, parseInt(b) - 1, c), w = date.getDay(), d = date.getDate();
         return Math.ceil(
             (d + 6 - w) / 7
         );
     };

     /**
      * 获取选择当前的第几周，当前的周一、周日
      * time 选择日期的时间戳
      */
     function getNowDateAndNowWeek(time) {
         //选中的时间戳
         var timestamp = time;
         var serverDate = new Date(time);

         //本周周日的的时间
         var sundayTiem = timestamp + ((7 - serverDate.getDay()) * 24 * 60 * 60 * 1000)
         var SundayData = new Date(sundayTiem);
         //年
         var tomorrowY = SundayData.getFullYear();
         //月
         var tomorrowM = (SundayData.getMonth() + 1 < 10 ? '0' + (SundayData.getMonth() + 1) : SundayData.getMonth() + 1);
         //日
         var tomorrowD = SundayData.getDate() < 10 ? '0' + SundayData.getDate() : SundayData.getDate();
         console.log('周日：  ' + tomorrowY + '-' + tomorrowM + '-' + tomorrowD);

         // 本周周一的时间
         var mondayTime = timestamp - ((serverDate.getDay() - 1) * 24 * 60 * 60 * 1000)
         var mondayData = new Date(mondayTime);
         //年
         var mondayY = mondayData.getFullYear();
         //月
         var mondayM = (mondayData.getMonth() + 1 < 10 ? '0' + (mondayData.getMonth() + 1) : mondayData.getMonth() + 1);
         //日
         var mondayD = mondayData.getDate() < 10 ? '0' + mondayData.getDate() : mondayData.getDate();
         var nowWeek = getMonthWeek(tomorrowY, tomorrowM, tomorrowD);
         //输出值
         var config = {
             SunDay: tomorrowY + '/' + tomorrowM + '/' + tomorrowD,
             Monday: mondayY + '/' + mondayM + '/' + mondayD,
             nowWeek: nowWeek
         }
         return config;
     }