js使用Date()获取本周，本月，本季度，本年的开始结束日期 输出yyyy-MM-dd HH:MM:SS 到 yyyy-MM-dd HH:MM:SS 格式

    //处理日期 
    choseDate(val) {
      var params;
      // var date = new Date();
      var now = new Date(); //当前日期
      var nowDayOfWeek = now.getDay(); //今天本周的第几天
      var nowDay = now.getDate(); //当前日
      var nowMonth = now.getMonth(); //当前月
      var nowYear = now.getYear(); //当前年
      nowYear += nowYear < 2000 ? 1900 : 0; //
      var lastMonthDate = new Date(); //上月日期
      lastMonthDate.setDate(1);
      lastMonthDate.setMonth(lastMonthDate.getMonth() - 1);
      var lastYear = lastMonthDate.getYear();
      var lastMonth = lastMonthDate.getMonth();
      //格式化日期：yyyy-MM-dd
      function formatDate(date) {
        var myyear = date.getFullYear();
        var mymonth = date.getMonth() + 1;
        var myweekday = date.getDate();
        if (mymonth < 10) {
          mymonth = "0" + mymonth;
        }
        if (myweekday < 10) {
          myweekday = "0" + myweekday;
        }
        return myyear + "-" + mymonth + "-" + myweekday;
      }
      function getMonthDays(myMonth) {
        var monthStartDate = new Date(nowYear, myMonth, 1);
        var monthEndDate = new Date(nowYear, myMonth + 1, 1);
        var days = (monthEndDate - monthStartDate) / (1000 * 60 * 60 * 24);
        return days;
      }
      //获得本季度的开始月份
      function getQuarterStartMonth() {
        var quarterStartMonth = 0;
        if (nowMonth < 3) {
          quarterStartMonth = 0;
        }
        if (2 < nowMonth && nowMonth < 6) {
          quarterStartMonth = 3;
        }
        if (5 < nowMonth && nowMonth < 9) {
          quarterStartMonth = 6;
        }
        if (nowMonth > 8) {
          quarterStartMonth = 9;
        }
        return quarterStartMonth;
      }

      function getDay(day) {
        var today = new Date();
        var targetday_milliseconds =
          today.getTime() + 1000 * 60 * 60 * 24 * day;
        today.setTime(targetday_milliseconds); //注意，这行是关键代码
        var tYear = today.getFullYear();
        var tMonth = today.getMonth();
        var tDate = today.getDate();
        tMonth = doHandleMonth(tMonth + 1);
        tDate = doHandleMonth(tDate);
        return tYear + "-" + tMonth + "-" + tDate;
      }

      function doHandleMonth(month) {
        var m = month;
        if (month.toString().length == 1) {
          m = "0" + month;
        }
        return m;
      }
      // var flag = parseInt(params);
      switch (val) {
        case 1:
          // 今日
          var startStr = now.format("yyyy-MM-dd 00:00:00");
          var endStr = now.format("yyyy-MM-dd 23:59:59");
          params = {
            startDate: startStr,
            endDate: endStr
          };
          break;
        case 2:
          // 本周
          var weekStartDate = new Date(
            nowYear,
            nowMonth,
            nowDay - nowDayOfWeek + 1
          );
          var start = formatDate(weekStartDate);
          var weekEndDate = new Date(
            nowYear,
            nowMonth,
            nowDay + (6 - nowDayOfWeek)
          );
          // var end = formatDate(weekEndDate);
          var end = formatDate(new Date());
          // var start = getDay(-6);
          // var end = getDay(0);
          params = {
            startDate: start + " " + "00:00:00",
            endDate: end + " " + "23:59:59"
          };
          break;
        case 3:
          // 本月
          var monthStartDate = new Date(nowYear, nowMonth, 1);
          var start = formatDate(monthStartDate);
          var monthEndDate = new Date(
            nowYear,
            nowMonth,
            getMonthDays(nowMonth)
          );
          var end = formatDate(monthEndDate);
          params = {
            startDate: start + " " + "00:00:00",
            endDate: end + " " + "23:59:59"
          };
          break;
        case 4:
          // 本季度
          var quarterStartDate = new Date(nowYear, getQuarterStartMonth(), 1);
          var start = formatDate(quarterStartDate);
          var quarterEndMonth = getQuarterStartMonth() + 2;
          var quarterStartDate = new Date(
            nowYear,
            quarterEndMonth,
            getMonthDays(quarterEndMonth)
          );
          var end = formatDate(quarterStartDate);
          params = {
            startDate: start + " " + "00:00:00",
            endDate: end + " " + "23:59:59"
          };
          break;
        case 5:
          // 本年
          var start = now.format("yyyy-01-01 00:00:00");
          var end = now.format("yyyy-12-31 23:59:59");
          params = {
            startDate: start,
            endDate: end
          };
          break;
      }
      return params;
    },