Question

我每周（例如星期五）生成报告，我需要每个月的结束日期。如果是新月，则返回该月的最后日期。我在这里第一次约会：-

var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);

但无法继续。

Answer 1

JavaScript并没有直接提供获取此类信息的功能，但是您可以自行计算，例如，计算每月的最后一个星期五，例如

function lastFridayOfMonth(year, month) {
    // if month will start from one not from 0  then we will have month + 1
    var lastDay = new Date(year, month + 2, 0); 
    var lastDayNumber = 5;
    if(lastDay.getDay() < lastDayNumber) {
        lastDay.setDate(lastDay.getDate() - 7);
    }
    lastDay.setDate(lastDay.getDate() - (lastDay.getDay() - lastDayNumber));
    return lastDay;
}

Answer 2

尝试使用以下功能。

function getWeekEndDates(date) {
  let year = date.getFullYear();
  let month = date.getMonth();
  let firstDay = new Date(year, month, 1);
  let lastDay = new Date(year, month + 1, 0);
  let weekEnds = [];

  let dateFriday = firstDay;
  if (firstDay.getDay() !== 5) {
    dateFriday = new Date(year, month, 1 + ((12 - firstDay.getDay()) % 7));
    weekEnds.push(firstDay);
  }

  while (dateFriday.getMonth() === month) {
    weekEnds.push(dateFriday);
    dateFriday = new Date(year, month, dateFriday.getDate() + 7);
  }

  if (lastDay.getDay() !== 5) {
    weekEnds.push(lastDay);
  }

  return weekEnds;
}

getWeekEndDates(new Date()).forEach(x => console.log(x.toDateString()));
getWeekEndDates(new Date(2020, 0, 1)).forEach(x => console.log(x.toDateString()));
getWeekEndDates(new Date(2021, 0, 1)).forEach(x => console.log(x.toDateString()));

Answer 3

签出RRule软件包。它为您提供了日期和时间间隔的多种可能性。它适用于日历等规则。

根据您的情况。每个星期五：

import { RRule } from 'rrule'

const rule = new RRule({
  freq: RRule.WEEKLY,
  interval: 1,
  byweekday: [RRule.FR],
})

// fridays in interval, you will got an array of dates
rule.between(new Date(Date.UTC(2012, 7, 1)), new Date(Date.UTC(2012, 8, 1)))

当前月份的一周的结束日期

3 个答案: