Moment js按周获取一个月中的特定日期和星期几

Question

如何使用 moment js 获取给定月份的第二个星期二或给定月份的第三个星期四。

我尝试寻找解决方案，但没有成功。我自己写了它并在下面发布了答案，如果您有更好的解决方案，您可以回答您的实现。

Answer 1

这是我在评论中链接的答案的更新版本。我曾经weekday使用区域设置感知的一周中的某一天，day如果您总是希望星期日为 0 和星期六为 6 ，则可以使用。

var getGivenDateOfMonth = function (startDate, dayOfWeek, weekNumber) {
  // Start of the month of the given startDate
  var myMonth = moment(startDate).startOf('month');
  // dayOfWeek of the first week of the month
  var firstDayOfWeek = myMonth.clone().weekday(dayOfWeek);
  // Check if first firstDayOfWeek is in the given month
  if( firstDayOfWeek.month() != myMonth.month() ){
      weekNumber++;
  }
  // Return result
  return firstDayOfWeek.add(weekNumber-1, 'weeks');
}

// Examples
var secondMondayOfJuly = getGivenDateOfMonth('2017-07-10', 1, 2);
console.log(secondMondayOfJuly.format());
var thirdFridayOfJuly = getGivenDateOfMonth('2017-07-10', 5, 3);
console.log(thirdFridayOfJuly.format());

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>

Answer 2

//get a preferred day of a month
var getGivenDateOfMonth = function (startDate, dayOfWeek, weekNumber) {
            var startOfMonth = moment(startDate).utc().startOf('month').startOf('isoweek');
            var dayOne = moment((moment(startDate, "YYYY-MM-DD").format("YYYY-MM") + "-01"),"YYYY-MM-DD");
            var studyDate;
            if (dayOne.isoWeekday() === 1) {
                studyDate = moment(startDate).utc().startOf('month').startOf('isoweek').add(dayOfWeek - 1, 'days')
                    .add(weekNumber, 'w');
            }
            else if (dayOne.isoWeekday() <= dayOfWeek) {
                studyDate = moment(startDate).utc().startOf('month').startOf('isoweek').add(dayOfWeek - 1, 'days')
                    .add(weekNumber - 1, 'w');
            } else {
                studyDate = moment(startDate).utc().startOf('month').startOf('isoweek').add(dayOfWeek - 1, 'days')
                    .add(weekNumber, 'w');
            }
            if (studyDate.month() == startOfMonth.month()) {
                studyDate = studyDate.subtract(1, 'w');
            }
            return studyDate;
        };

startDate是给定月份中的日期。
dayOfWeek是 js ISO 星期几，
weeknumber是你想要的周数（1,2,3,4）