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javascriptmomentjs
h_a86
h_a86

Reputation: 281

moment JS get number of weeks in a month

I am trying to calculate number of weeks in a month using moment js. But I am getting wrong results for some months like May 2015 and August 2015.

I am using this code.

var start = moment().startOf('month').format('DD');
var end = moment().endOf('month').format('DD');
var weeks = (end-start+1)/7;
weeks = Math.ceil(weeks);

Is there any prebuilt method in moment JS for getting number of weeks.

Upvotes: 1

Views: 26967

Answers (15)

Sylvain Gourio
Sylvain Gourio

Reputation: 31

Simply way using es6 to get an array of week numbers for a given year and month.

/**
 * Returns an array of week numbers for a given year and month, where each week
 * contains at least one day of the given month.
 *
 * @param {number} year - The year of the month (e.g., 2023)
 * @param {number} month - The month as a number (e.g., 0 for January, 11 for December)
 * @returns {number[]} An array of week numbers (e.g., [1, 2, 3, 4])
 */
const getWeeksOfMonth = (year, month) => {
  const isWeekInMonth = (month, week) => week.startOf('week').month() === month || week.endOf('week') === month
  return Array
    .from({ length: moment().year(year).weeksInYear() }, (_, i) => i + 1)
    .filter((weekNumber) => isWeekInMonth(month, moment().year(year).isoWeek(weekNumber)))
}

Upvotes: 0

Tadej Slemenšek
Tadej Slemenšek

Reputation: 112

/UPDATE/
Solution below did not take in consideration jump to the new year. Here is the improved solution.

const getNumberOfWeeksInAMonth = (currentMoment: moment.Moment) => {
    const currentMomentCopy = cloneDeep(currentMoment)
    const startOfMonth = currentMomentCopy.startOf('month')
    const startOfISOWeek = startOfMonth.startOf('isoWeek')

    let numberOfWeeks = 0;
    
    do {
        numberOfWeeks++
        MomentManager.addWeek(startOfISOWeek)
    } while (currentMoment.month() === startOfISOWeek.month())

    return numberOfWeeks;
}

I have found another solution with momentjs.

const getNumberOfWeeksInMonth = (moment: moment.Moment) => {
  const startWeek = moment.startOf('month').isoWeek()
  const endWeek = moment.endOf('month').isoWeek()
  return endWeek - startWeek + 1
}

Upvotes: 0

Gopi Linga
Gopi Linga

Reputation: 11

javaScript version here

var year = 2021
        var  month = 6 
        var  startDate = moment([year, month])

        //Get the first and last day of the month
       var firstDay = moment(startDate).startOf('month')
       var  endDay = moment(startDate).endOf('month')
     
        //Create a range for the month we can iterate through
       var  monthRange = moment.range(firstDay, endDay)
       
        //Get all the weeks during the current month
       var  weeks = []
        var indexOf = [].indexOf;

        monthRange.by('days', function (moment) {
            var ref;
            if (ref = moment.week(), indexOf.call(weeks, ref) < 0) {
                return weeks.push(moment.week());
            }
        });
      

        var calendar, firstWeekDay, i, lastWeekDay, len, week, weekRange;

        calendar = [];

        for (i = 0, len = weeks.length; i < len; i++) {
            week = weeks[i];
            // Create a range for that week between 1st and 7th day
            firstWeekDay = moment().week(week).day(0);
            lastWeekDay = moment().week(week).day(6);
            weekRange = moment.range(firstWeekDay, lastWeekDay);
         
            // Add to the calendar
            calendar.push(weekRange);
        }

Upvotes: 1

Igor Maf
Igor Maf

Reputation: 1

If you have selectedDate value that is give you opportunity to detect which month is active now:

private calculateNumberOfWeeks(): number {
    const end = moment(this.selectedDate).endOf('month');

    const startDay = moment(this.selectedDate)
      .startOf('month')
      .day();

    const endDay = end.day();
    const endDate = end.date();

    return (startDay - 1 + endDate + (endDay === 0 ? 0 : 7 - endDay)) / 7;
  }

Upvotes: 0

Thanaruby Nanthagopal
Thanaruby Nanthagopal

Reputation: 614

var month = moment().month();
var startOfMonth = month.startOf("month");
var endOfMonth = month.endOf("month");
var startWeekNumber = startOfMonth.isoWeek();
var endWeekNumber = endOfMonth.isoWeek();
var numberOfWeeks = (endWeekNumber - startWeekNumber + 1);
console.log(numberOfWeeks);

Upvotes: 0

user8310317
user8310317

Reputation:

Throwing this into the mix

import moment from "moment";
export const calcWeeksInMonth = date => {
  let weekMonthEnds = moment(date)
    .date(moment(date).daysInMonth())
    .week();
  let weekMonthStarts = moment(date)
    .date(1)
    .week();

  return weekMonthEnds < weekMonthStarts
    ? moment(date).isoWeeksInYear() - weekMonthStarts + 1
    : weekMonthEnds - weekMonthStarts + 1;
};

Upvotes: 0

Erik
Erik

Reputation: 188

Here is a simple way of doing it (based on a solution posted above):

const calcWeeksInMonth = (momentDate) => {
  const dateFirst = moment(momentDate).date(1)
  const dateLast = moment(momentDate).date(momentDate.daysInMonth())
  const startWeek = dateFirst.isoWeek()
  const endWeek = dateLast.isoWeek()

  if (endWeek < startWeek) {
    // cater to end of year (dec/jan)
    return dateFirst.weeksInYear() - startWeek + 1 + endWeek
  } else {
    return endWeek - startWeek + 1
  }
}

As far as I can tell, it works correctly for any date thrown at it, but feedback is always welcome!

Upvotes: 0

jonruna
jonruna

Reputation: 121

EDIT:

NEW and hopefully very correct implementation:

function calcWeeksInMonth(date: Moment) {
  const dateFirst = moment(date).date(1);
  const dateLast = moment(date).date(date.daysInMonth());
  const startWeek = dateFirst.isoWeek();
  const endWeek = dateLast.isoWeek();

  if (endWeek < startWeek) {
    // Yearly overlaps, month is either DEC or JAN
    if (dateFirst.month() === 0) {
      // January
      return endWeek + 1;
    } else {
      // December
      if (dateLast.isoWeekday() === 7) {
        // Sunday is last day of year
        return endWeek - startWeek + 1;
      } else {
        // Sunday is NOT last day of year
        return dateFirst.isoWeeksInYear() - startWeek + 1;
      }
    }
  } else {
    return endWeek - startWeek + 1;
  }
}

Outputs the following values for the following dates:

calcWeeksInMonth(moment("2016-12-01")); // 5

calcWeeksInMonth(moment("2017-01-01")); // 6
calcWeeksInMonth(moment("2017-02-01")); // 5
calcWeeksInMonth(moment("2017-03-01")); // 5
calcWeeksInMonth(moment("2017-04-01")); // 5
calcWeeksInMonth(moment("2017-05-01")); // 5
calcWeeksInMonth(moment("2017-06-01")); // 5
calcWeeksInMonth(moment("2017-07-01")); // 6
calcWeeksInMonth(moment("2017-08-01")); // 5
calcWeeksInMonth(moment("2017-09-01")); // 5
calcWeeksInMonth(moment("2017-10-01")); // 6
calcWeeksInMonth(moment("2017-11-01")); // 5
calcWeeksInMonth(moment("2017-12-01")); // 5

calcWeeksInMonth(moment("2018-01-01")); // 5

OLD and very incorrect implementation:

calcWeeksInMonth(date) {
    const dateFirst = moment(date).date(1)
    const dateLast = moment(date).date(date.daysInMonth())
    const startWeek = dateFirst.week()
    const endWeek = dateLast.week()
    if (endWeek < startWeek) {
        return dateFirst.weeksInYear() - startWeek + 1 + endWeek
    } else {
        return endWeek - startWeek + 1
    }
}

This seems to output correct results, feedback welcome if there is something I missed!

Upvotes: 2

user3507286
user3507286

Reputation: 1

  function weeksInMonth(date = null){
    let firstDay = moment(date).startOf('month');
    let endDay = moment(date).endOf('month');

    let weeks = [];
    for (let i = firstDay.week(); i <= endDay.week(); i++){
      weeks.push(i)
    }

    return weeks;
  }

Upvotes: 0

Bigtrizzy
Bigtrizzy

Reputation: 103

I have not seen a solution that works in all circumstances. I tried all of these but they all are flawed in one way or another. Ditto with several moment.js github threads. This was my crack at it:

getNumberOfWeeksInMonth = (momentDate) => {
  const monthStartWeekNumber = momentDate.startOf('month').week();

  const distinctWeeks = {
    [monthStartWeekNumber]: true
  };

  let startOfMonth = momentDate.clone().startOf('month');
  let endOfMonth = momentDate.clone().endOf('month');

  //  this is an 'inclusive' range -> iterates through all days of a month
  for (let day = startOfMonth.clone(); !day.isAfter(endOfMonth); day.add(1, 'days')) {
    distinctWeeks[day.week()] = true
  }

  return Object.keys(distinctWeeks).length;
}

Upvotes: 0

Kanish Mathew
Kanish Mathew

Reputation: 905

It display the list of weeks in a month with 'moment.js'.
It has been written in typescript with angular 6+.

Install moment with 'npm i moment'

Inside the ts file.

weeks_in_month() {
    let year = 2019;  // change year
    let month = 4; // change month here
    let startDate = moment([year, month - 1])
    let endDate = moment(startDate).endOf('month');

    var dates = [];
    var weeks = [];

    var per_week = [];
    var difference = endDate.diff(startDate, 'days');

    per_week.push(startDate.toDate())
    let index = 0;
    let last_week = false;
    while (startDate.add(1, 'days').diff(endDate) < 0) {
      if (startDate.day() != 0) {
        per_week.push(startDate.toDate())
      }
      else {
        if ((startDate.clone().add(7, 'days').month() == (month - 1))) {
          weeks.push(per_week)
          per_week = []
          per_week.push(startDate.toDate())
        }
        else if (Math.abs(index - difference) > 0) {
          if (!last_week) {
            weeks.push(per_week);
            per_week = [];
          }
          last_week = true;
          per_week.push(startDate.toDate());
        }
      }
      index += 1;
      if ((last_week == true && Math.abs(index - difference) == 0) ||
        (Math.abs(index - difference) == 0 && per_week.length == 1)) {
        weeks.push(per_week)
      }
      dates.push(startDate.clone().toDate());
    }
    console.log(weeks);
}

Result:

Array of date moments.

[Array(6), Array(7), Array(7), Array(7), Array(3)]

0: (6) [Mon Apr 01 2019 00:00:00 GMT+0530 (India Standard Time),  
Tue Apr 02 2019 00:00:00 GMT+0530 (India Standard Time),  
Wed Apr 03 2019 00:00:00 GMT+0530 (India Standard Time),  
Thu Apr 04 2019 00:00:00 GMT+0530 (India Standard Time),  
Fri Apr 05 2019 00:00:00 GMT+0530 (India Standard Time),  
Sat Apr 06 2019 00:00:00 GMT+0530 (India Standard Time)]

1: (7) [Sun Apr 07 2019 00:00:00 GMT+0530 (India Standard Time),  
Mon Apr 08 2019 00:00:00 GMT+0530 (India Standard Time),  
Tue Apr 09 2019 00:00:00 GMT+0530 (India Standard Time),  
Wed Apr 10 2019 00:00:00 GMT+0530 (India Standard Time),  
Thu Apr 11 2019 00:00:00 GMT+0530 (India Standard Time),  
Fri Apr 12 2019 00:00:00 GMT+0530 (India Standard Time),  
Sat Apr 13 2019 00:00:00 GMT+0530 (India Standard Time)]

2: (7) [Sun Apr 14 2019 00:00:00 GMT+0530 (India Standard Time),  
Mon Apr 15 2019 00:00:00 GMT+0530 (India Standard Time),  
Tue Apr 16 2019 00:00:00 GMT+0530 (India Standard Time),  
Wed Apr 17 2019 00:00:00 GMT+0530 (India Standard Time),  
Thu Apr 18 2019 00:00:00 GMT+0530 (India Standard Time),  
Fri Apr 19 2019 00:00:00 GMT+0530 (India Standard Time),  
Sat Apr 20 2019 00:00:00 GMT+0530 (India Standard Time)]

3: (7) [Sun Apr 21 2019 00:00:00 GMT+0530 (India Standard Time),  
Mon Apr 22 2019 00:00:00 GMT+0530 (India Standard Time),  
Tue Apr 23 2019 00:00:00 GMT+0530 (India Standard Time),  
Wed Apr 24 2019 00:00:00 GMT+0530 (India Standard Time),  
Thu Apr 25 2019 00:00:00 GMT+0530 (India Standard Time),  
Fri Apr 26 2019 00:00:00 GMT+0530 (India Standard Time),  
Sat Apr 27 2019 00:00:00 GMT+0530 (India Standard Time)]

4: (3) [Sun Apr 28 2019 00:00:00 GMT+0530 (India Standard Time),  
Mon Apr 29 2019 00:00:00 GMT+0530 (India Standard Time),  
Tue Apr 30 2019 00:00:00 GMT+0530 (India Standard Time)]

Upvotes: 2

Noor
Noor

Reputation: 20150

Can be easily done using raw javascript:

function getNumWeeksForMonth(year,month){
              date = new Date(year,month-1,1);
              day = date.getDay();
              numDaysInMonth = new Date(year, month, 0).getDate();
              return Math.ceil((numDaysInMonth + day) / 7);
}

You get the day index of the first day, add it to the number of days to compensate for the number of days lost in the first week, divide by 7 and use ceil to add 1 for the simplest overflow in the next week

Upvotes: 2

JVitela
JVitela

Reputation: 2512


function getWeekNums(momentObj) {
    var clonedMoment = moment(momentObj), first, last;

    // get week number for first day of month
    first = clonedMoment.startOf('month').week();
    // get week number for last day of month
    last = clonedMoment.endOf('month').week();

    // In case last week is in next year
    if( first > last) {
        last = first + last;
    }
    return last - first + 1;
}

Upvotes: 1

guillaumepiot
guillaumepiot

Reputation: 381

I have created this gist that finds all the weeks in a given month and year. By calculated the length of calendar, you will know the number of weeks.

https://gist.github.com/guillaumepiot/095b5e02b4ca22680a50

# 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

Upvotes: 3

m0bi5
m0bi5

Reputation: 9452

This is the best way out , works well

moment.relativeTime.dd = function (number) {
    // round to the closest number of weeks
    var weeks = Math.round(number / 7);
    if (number < 7) {
        // if less than a week, use days
        return number + " days";
    } else {
        // pluralize weeks
        return weeks + " week" + (weeks === 1 ? "" : "s"); 
    }
}

Source:How to get duration in weeks with Moment.js?

Upvotes: 0

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