react-dates/esm/utils/getCalendarMonthWeeks.js

A responsive and accessible date range picker component built with React

import moment from 'moment';
import { WEEKDAYS } from '../constants';
export default function getCalendarMonthWeeks(month, enableOutsideDays) {
  var firstDayOfWeek = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : moment.localeData().firstDayOfWeek();

  if (!moment.isMoment(month) || !month.isValid()) {
    throw new TypeError('`month` must be a valid moment object');
  }

  if (WEEKDAYS.indexOf(firstDayOfWeek) === -1) {
    throw new TypeError('`firstDayOfWeek` must be an integer between 0 and 6');
  } // set utc offset to get correct dates in future (when timezone changes)


  var firstOfMonth = month.clone().startOf('month').hour(12);
  var lastOfMonth = month.clone().endOf('month').hour(12); // calculate the exact first and last days to fill the entire matrix
  // (considering days outside month)

  var prevDays = (firstOfMonth.day() + 7 - firstDayOfWeek) % 7;
  var nextDays = (firstDayOfWeek + 6 - lastOfMonth.day()) % 7;
  var firstDay = firstOfMonth.clone().subtract(prevDays, 'day');
  var lastDay = lastOfMonth.clone().add(nextDays, 'day');
  var totalDays = lastDay.diff(firstDay, 'days') + 1;
  var currentDay = firstDay.clone();
  var weeksInMonth = [];

  for (var i = 0; i < totalDays; i += 1) {
    if (i % 7 === 0) {
      weeksInMonth.push([]);
    }

    var day = null;

    if (i >= prevDays && i < totalDays - nextDays || enableOutsideDays) {
      day = currentDay.clone();
    }

    weeksInMonth[weeksInMonth.length - 1].push(day);
    currentDay.add(1, 'day');
  }

  return weeksInMonth;
}