Get all the weeks in a given month and year using Moment.js

weeks_in_month.coffee

# year and month are variables
year = 2015
month = 7 # August (0 indexed)
startDate = moment([year, month])

# Get the first and last day of the month
firstDay = moment(startDate).startOf('month')
endDay = moment(startDate).endOf('month')

# Create a range for the month we can iterate through
monthRange = moment.range(firstDay, endDay)

# Get all the weeks during the current month
weeks = []
monthRange.by('days', (moment)->
    if moment.week() not in weeks
        weeks.push(moment.week())
)

# Create a range for each week
calendar = []
for week in weeks
    # Create a range for that week between 1st and 7th day
    firstWeekDay = moment().week(week).day(1)
    lastWeekDay = moment().week(week).day(7)
    weekRange = moment.range(firstWeekDay, lastWeekDay)
    
    # Add to the calendar
    calendar.push(weekRange)

console.log calendar

range function does not even exist, right?

You need https://github.com/rotaready/moment-range

In line 24 and 25 the initial parameters for the date are missing.

translated to javascript:
npm install moment moment-range

import * as Moment from 'moment';
import { extendMoment } from 'moment-range';

export const getDaysInAMonth = (year = +Moment().format("YYYY"), month = +Moment().format("MM") - 1) => {
    const moment = extendMoment(Moment);
    const startDate = moment([year, month]);

    const firstDay = moment(startDate).startOf('month')
    const endDay = moment(startDate).endOf('month')

    const monthRange = moment.range(firstDay, endDay)
    const weeks = [];
    const days = Array.from(monthRange.by('day'));
    days.forEach(it => {
        if (!weeks.includes(it.week())) {
            weeks.push(it.week());
        }
    })

    const calendar = []
    weeks.forEach(week => {
        const firstWeekDay = moment([year, month]).week(week).day(1)
        const lastWeekDay = moment([year, month]).week(week).day(7)
        const weekRange = moment.range(firstWeekDay, lastWeekDay)
        calendar.push(Array.from(weekRange.by('day')));
    })

    return calendar;
}

thanks for your code! :)

Good observation, would default to current year otherwise.

I found a problem, February 2021 returns March 1-7 as a week (instead of stopping at February 22-28)

Ok, changing firstWeekDay to 0 and lastWeekDay to 6 (week starts at Sunday) fixes the problem:

const firstWeekDay = moment([year, month]).week(week).day(0);
const lastWeekDay = moment([year, month]).week(week).day(6);