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Javascript to count the number of days for a specific month between two dates [duplicate]

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How to calculate number of days between two dates?
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Closed last month.
I am new to javascript.
I have specific month columns (9/30/2022, 10/31/2022,11/30/2022). I have a contract with a start date and end date (spanning multiple months).
I need to determine the number of days the contract was active for a specific month column.
Example:
Contact Start Date: 09/15/2022
Contract End Date: 10/24/2022
Number of days the contract was active in Sept 2022 is 16.
I found the code below that gives me the contract period broken down for each month (i.e.) **9 - 17; 10 - 23; **
Thank you in advance for any assistance.
I found this code
function getDays() {
var dropdt = new Date(document.getElementById("arr").value);
var pickdt = new Date(document.getElementById("dep").value);
var result = "";
for (var year = dropdt.getFullYear(); year <= pickdt.getFullYear(); year++) {
var firstMonth = (year == dropdt.getFullYear()) ? dropdt.getMonth() : 0;
var lastMonth = (year == pickdt.getFullYear()) ? pickdt.getMonth() : 11;
for (var month = firstMonth; month <= lastMonth; month++) {
var firstDay = (year === dropdt.getFullYear() && month === firstMonth) ? dropdt.getDate() : 1;
var lastDay = (year === pickdt.getFullYear() && month === lastMonth) ? pickdt.getDate() : 0;
var lastDateMonth = (lastDay === 0) ? (month + 1) : month
var firstDate = new Date(year, month, firstDay);
var lastDate = new Date(year, lastDateMonth, lastDay);
result += (month + 1) + " - " + parseInt((lastDate - firstDate) / (24 * 3600 * 1000) + 1) + "; ";
}
}
return result;
}
function cal() {
if (document.getElementById("dep")) {
document.getElementById("number-of-dates").value = getDays();
}
Calculate
`

The following snippet will generate an object res with the keys being zero-based month-indexes ("8" is for September, "9" for October, etc.) and the values are the number of days for each of these months:
const start=new Date("2022-09-15");
const end=new Date("2022-11-24");
let nextFirst=new Date(start.getTime()), month, days={};
do {
month=nextFirst.getMonth();
nextFirst.setMonth(month+1);nextFirst.setDate(1);
days[month]=Math.round(((nextFirst<end?nextFirst:end)-start)/86400000);
start.setTime(nextFirst.getTime());
} while(nextFirst<end)
console.log(days);
This can be extended into a more reliable function returning a year-month combination:
function daysPerMonth(start,end){
let nextFirst=new Date(start.getTime()), year, month, days={};
do {
year=nextFirst.getFullYear();
month=nextFirst.getMonth();
nextFirst.setMonth(month+1);nextFirst.setDate(1);
days[`${year}-${String(1+month).padStart(2,"0")}`]=Math.round(((nextFirst<end?nextFirst:end)-start)/86400000);
start.setTime(nextFirst.getTime());
} while(nextFirst<end)
return days;
}
[["2022-09-15","2022-11-24"],["2022-11-29","2023-02-04"]].forEach(([a,b])=>
console.log(daysPerMonth(new Date(a),new Date(b))));

Managing and calculating dates, times, and date-times are notoriously finicky in javascript and across browsers. Rather than trying to define your own logic for this use the famous Moment.js library.
In particular to calculate the length between two dates you can utilize the diff function between two moments
var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 25]);
var diff = a.diff(b, 'days') // 1
console.log(diff);
<script src="https://momentjs.com/downloads/moment.js"></script>
The supported measurements are years, months, weeks, days, hours, minutes, and seconds.

Calculate days excluding weekend and holiday in JavaScript

I am trying to write a code where total days will be counted excluding weekends and custom defined holiday. I searched through stackoverflow and adobe forum to find a solution and came with below code.
If public holiday falls in a working day (Saturday-Wednesday) it is excluding from calculation.
My problem is that if public holiday falls in weekend (Thursday-Friday), it is deducting for both (holiday & weekend). Suppose leave duration is 18/09/2018-22/09/2018, total count 2 days is showing in place of 3. Again for 17/10/2018-21/10/2018, total count 1 day is showing in place of 3 days.
Any help or any idea to solve the problem would be great!
Regards
//Thursday and Friday will be excluded as weekend.
var start = this.getField("From").value;
// get the start date value
var end = this.getField("To").value;
var end = util.scand("dd/mm/yyyy H:MM:SS", end + " 0:00:00");
var start =util.scand("dd/mm/yyyy H:MM:SS", start + " 0:00:00");
event.value = dateDifference(start, end);
function dateDifference(start, end) {
// Copy date objects so don't modify originals
var s = new Date(+start);
var e = new Date(+end);
// Set time to midday to avoid daylight saving and browser quirks
s.setHours(12,0,0,0);
e.setHours(12,0,0,0);
// Get the difference in whole days
var totalDays = Math.round((e - s) / 8.64e7);
// Get the difference in whole weeks
var wholeWeeks = totalDays / 7 | 0;
// Estimate business days as number of whole weeks * 5
var days = wholeWeeks * 5;
// If not even number of weeks, calc remaining weekend days
if (totalDays % 7) {
s.setDate(s.getDate() + wholeWeeks * 7);
while (s < e) {
s.setDate(s.getDate() + 1);
// If day isn't a Thursday or Friday, add to business days
if (s.getDay() != 4 && s.getDay() != 5) {
++days;
}
}
}
var hdayar = ["2018/02/21","2018/03/17","2018/03/26","2018/04/14","2018/05/01","2018/08/15","2018/09/2 1","2018/10/18","2018/10/19","2018/12/16","2018/12/25"];
//test for public holidays
var phdays = 0;
for (var i = 0; i <hdayar.length; i++){
if ((Date.parse(hdayar[i]) >= Date.parse(start)) && (Date.parse(hdayar[i]) <= Date.parse(end))) {phdays ++;}}
return days-phdays + 1;
}

You should use a library for this rather than reinventing the wheel.
But if you want to do it yourself you could use .getDay to check if the public holidays are on a weekend.
var weekend = [4, 5], // for Thursday, Friday
holDate, holDay;
for (var i = 0; i < hdayar.length; i++){
holDate = Date.parse(hdayar[i]);
holDay = new Date(holDate).getDay()
if (weekend.indexOf(holDay) == -1 && holDate >= Date.parse(start) && holDate <= Date.parse(end)) {
phdays ++;
}
}
phdays will now contain the number of non-weekend public holidays within the range.

Just have the same requirement and this is the my work around.Hope it helps other
var holiday = ["4/18/2019", "4/19/2019", "4/20/2019", "4/25/2019", "4/26/2019"];
var startDate = new Date();
var endDate = new Date(startDate.setDate(startDate.getDate() + 1));
for (i = 0; i < holiday.length; i++) {
var date = endDate.getDate();
var month = endDate.getMonth() + 1; //Months are zero based
var year = endDate.getFullYear();
if ((month + '/' + date + '/' + year) === (holiday[i])) {
endDate = new Date(endDate.setDate(endDate.getDate() + 1));
if (endDate.getDay() == 6) {
endDate = new Date(endDate.setDate(endDate.getDate() + 2));
} else if (endDate.getDay() == 0) {
endDate = new Date(endDate.setDate(endDate.getDate() + 1));
}
}
}
Here, end date gives you next working day.Here,I'm ignoring current day and start comparing from Next day whether it's holiday or weekend.You can customize dateTime as per your requirement (month + '/' + date + '/' + year).Careful whenever you compares two dates with each other. Because it looks same but actually it's not.So customize accordingly.

Why its not giving me the correct total month?

Why it's not giving me the correct total month? (with compared to current mm-yyyy)
function get_total_month(mm,yyyy) {
// custom inputs
var start_date = new Date(yyyy, mm, 01);
// current date
var today_date = new Date();
var today_year = today_date.getFullYear();
var today_month = today_date.getMonth();
var today_day = today_date.getDate();
var end_date = new Date(new Date(today_year, today_month, today_day));
// compare the given date with current date to find the total months
var total_months = (end_date.getFullYear() - start_date.getFullYear())*12 + (end_date.getMonth() - start_date.getMonth());
return total_months;
}
alert(
get_total_month(01, 2014)
);
Giving me: 20 instead of 22

That's because the Date.prototype.getMonth method returns a 0-11 number. So:
January = 0
February = 1
...
December = 11

I think this is what you are looking for, it is another version of your code. But I think is shorter and easier to understand. What do you think?
(I added the +2 to adjust the result to what you are expecting the function to return)
function monthDifference(startDate) {
var months;
var currentDate = new Date();
months = (currentDate.getFullYear() - startDate.getFullYear()) * 12;
months -= startDate.getMonth() + 1;
months += currentDate.getMonth();
return months <= 0 ? 0 : (months + 2);
}
alert(monthDifference(new Date(2014,0)) );
alert(monthDifference(new Date(2013,11)) );

How to loop through weekdays in a month?

monthDays = 31;
dayOfMonth = 9;
weekOfMonth = 2;
startDay = weekStartingDate (weekOfMonth); // function return 8
// startDay could be 8, 15, 22 or 28
for (var day = startDay; day < (startDay+7) ; day++)
{
//stuff
}
The problem is, when startDay is 29+, that (startDay+7) exceds monthDays
I want to loop through days considering weekdays ranges.

You should define the limit value to your for loop
for (var day = startDay; day < ((startDay+7) > monthDays ? monthDays : (startDay+7)) ; day++)
{
//stuff
}

monthDays = 31;
dayOfMonth = 9;
weekOfMonth = 2;
startDay = weekStartingDate (weekOfMonth); // function return 8
for (var day = startDay; day < (startDay+7) ; day++)
{
//stuff
if(x >=31 ){
break;
}
}

Why not use a tertiary?
monthDays = 31;
dayOfMonth = 9;
weekOfMonth = 2;
startDay = weekStartingDate (weekOfMonth); // function return 8
var maxDay = (startDay+7) > monthDays ? monthDays : (startDay+7)
// startDay could be 8, 15, 22 or 28
for (var day = startDay; day <= maxDay ; day++)
{
//stuff
}

Instead of (startDay+7) use (startDay+7)%monthDays

Not quite sure what you are trying to do, but it seem you are trying to get the dates for a week that are in the same month.
The functions below do that. getWeekStartDate returns a Date for the start of the week for a given date, optionally starting on Monday or Sunday. getNext7DatesInMonth gets up to 7 days from the given a date in the same month.
The result is an array of numbers for the required dates.
/*
** #param {Date} date
** #param {boolean} weekStartsOnMon - true if week starts on Monday
** #returns {Date} - new date object for first day of week
*/
function getWeekStartDate(date, weekStartsOnMon) {
var d = new Date(+date);
var dayNum = d.getDay();
// If start of week is Monday
if (weekStartsOnMon) {
d.setDate(d.getDate() - (dayNum? dayNum : 7) +1)
;
// If start of week is Sunday
} else {
d.setDate(d.getDate() - d.getDay());
}
return d;
}
/*
** For the given date, get the dates in the week for the same month.
**
** #param {Date} date
** #param {boolean} weekStartsOnMon - true if week starts on Monday
** #returns {Array} - String dates for rest of week in same month as date
*/
function getNext7DatesInMonth(date){
var start = new Date(+date);
var monthNum = start.getMonth();
var weekDates = [];
var i = 7;
while (monthNum == start.getMonth() && i--) {
weekDates.push(start.getDate());
start.setDate(start.getDate() + 1);
}
return weekDates;
}
// Start week on Sunday
var d = new Date(2015,4,31)
console.log(d + ': ' + getNext7DatesInMonth(getWeekStartDate(d, false))); // 31
// Start week on Monday
var d = new Date(2015,4,31)
console.log(d + ': ' + getNext7DatesInMonth(getWeekStartDate(d, true))); // 25,26,27,28,29,30,31
You could do a similar function without Date objects based on getting the number of days in the month, but Date objects are convenient.

Get Weeks In Month Through Javascript

In Javascript, how do I get the number of weeks in a month? I can't seem to find code for this anywhere.
I need this to be able to know how many rows I need for a given month.
To be more specific, I would like the number of weeks that have at least one day in the week (a week being defined as starting on Sunday and ending on Saturday).
So, for something like this, I would want to know it has 5 weeks:
S M T W R F S
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31
Thanks for all the help.

Weeks start on Sunday
This ought to work even when February doesn't start on Sunday.
function weekCount(year, month_number) {
// month_number is in the range 1..12
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var used = firstOfMonth.getDay() + lastOfMonth.getDate();
return Math.ceil( used / 7);
}
Weeks start on Monday
function weekCount(year, month_number) {
// month_number is in the range 1..12
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var used = firstOfMonth.getDay() + 6 + lastOfMonth.getDate();
return Math.ceil( used / 7);
}
Weeks start another day
function weekCount(year, month_number, startDayOfWeek) {
// month_number is in the range 1..12
// Get the first day of week week day (0: Sunday, 1: Monday, ...)
var firstDayOfWeek = startDayOfWeek || 0;
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var numberOfDaysInMonth = lastOfMonth.getDate();
var firstWeekDay = (firstOfMonth.getDay() - firstDayOfWeek + 7) % 7;
var used = firstWeekDay + numberOfDaysInMonth;
return Math.ceil( used / 7);
}

None of the solutions proposed here don't works correctly, so I wrote my own variant and it works for any cases.
Simple and working solution:
/**
* Returns count of weeks for year and month
*
* #param {Number} year - full year (2016)
* #param {Number} month_number - month_number is in the range 1..12
* #returns {number}
*/
var weeksCount = function(year, month_number) {
var firstOfMonth = new Date(year, month_number - 1, 1);
var day = firstOfMonth.getDay() || 6;
day = day === 1 ? 0 : day;
if (day) { day-- }
var diff = 7 - day;
var lastOfMonth = new Date(year, month_number, 0);
var lastDate = lastOfMonth.getDate();
if (lastOfMonth.getDay() === 1) {
diff--;
}
var result = Math.ceil((lastDate - diff) / 7);
return result + 1;
};
you can try it here

This is very simple two line code. and i have tested 100%.
Date.prototype.getWeekOfMonth = function () {
var firstDay = new Date(this.setDate(1)).getDay();
var totalDays = new Date(this.getFullYear(), this.getMonth() + 1, 0).getDate();
return Math.ceil((firstDay + totalDays) / 7);
}
How to use
var totalWeeks = new Date().getWeekOfMonth();
console.log('Total Weeks in the Month are : + totalWeeks );

You'll have to calculate it.
You can do something like
var firstDay = new Date(2010, 0, 1).getDay(); // get the weekday january starts on
var numWeeks = 5 + (firstDay >= 5 ? 1 : 0); // if the months starts on friday, then it will end on sunday
Now we just need to genericize it.
var dayThreshold = [ 5, 1, 5, 6, 5, 6, 5, 5, 6, 5, 6, 5 ];
function GetNumWeeks(month, year)
{
var firstDay = new Date(year, month, 1).getDay();
var baseWeeks = (month == 1 ? 4 : 5); // only February can fit in 4 weeks
// TODO: account for leap years
return baseWeeks + (firstDay >= dayThreshold[month] ? 1 : 0); // add an extra week if the month starts beyond the threshold day.
}
Note: When calling, remember that months are zero indexed in javascript (i.e. January == 0).

function weeksinMonth(m, y){
y= y || new Date().getFullYear();
var d= new Date(y, m, 0);
return Math.floor((d.getDate()- 1)/7)+ 1;
}
alert(weeksinMonth(3))
// the month range for this method is 1 (january)-12(december)

The most easy to understand way is
<div id="demo"></div>
<script type="text/javascript">
function numberOfDays(year, month)
{
var d = new Date(year, month, 0);
return d.getDate();
}
function getMonthWeeks(year, month_number)
{
var $num_of_days = numberOfDays(year, month_number)
, $num_of_weeks = 0
, $start_day_of_week = 0;
for(i=1; i<=$num_of_days; i++)
{
var $day_of_week = new Date(year, month_number, i).getDay();
if($day_of_week==$start_day_of_week)
{
$num_of_weeks++;
}
}
return $num_of_weeks;
}
var d = new Date()
, m = d.getMonth()
, y = d.getFullYear();
document.getElementById('demo').innerHTML = getMonthWeeks(y, m);
</script>

using moment js
function getWeeksInMonth(year, month){
var monthStart = moment().year(year).month(month).date(1);
var monthEnd = moment().year(year).month(month).endOf('month');
var numDaysInMonth = moment().year(year).month(month).endOf('month').date();
//calculate weeks in given month
var weeks = Math.ceil((numDaysInMonth + monthStart.day()) / 7);
var weekRange = [];
var weekStart = moment().year(year).month(month).date(1);
var i=0;
while(i<weeks){
var weekEnd = moment(weekStart);
if(weekEnd.endOf('week').date() <= numDaysInMonth && weekEnd.month() == month) {
weekEnd = weekEnd.endOf('week').format('LL');
}else{
weekEnd = moment(monthEnd);
weekEnd = weekEnd.format('LL')
}
weekRange.push({
'weekStart': weekStart.format('LL'),
'weekEnd': weekEnd
});
weekStart = weekStart.weekday(7);
i++;
}
return weekRange;
} console.log(getWeeksInMonth(2016, 7))

ES6 variant, using consistent zero-based months index. Tested for years from 2015 to 2025.
/**
* Returns number of weeks
*
* #param {Number} year - full year (2018)
* #param {Number} month - zero-based month index (0-11)
* #param {Boolean} fromMonday - false if weeks start from Sunday, true - from Monday.
* #returns {number}
*/
const weeksInMonth = (year, month, fromMonday = false) => {
const first = new Date(year, month, 1);
const last = new Date(year, month + 1, 0);
let dayOfWeek = first.getDay();
if (fromMonday && dayOfWeek === 0) dayOfWeek = 7;
let days = dayOfWeek + last.getDate();
if (fromMonday) days -= 1;
return Math.ceil(days / 7);
}

You could use my time.js library. Here's the weeksInMonth function:
// http://github.com/augustl/time.js/blob/623e44e7a64fdaa3c908debdefaac1618a1ccde4/time.js#L67
weeksInMonth: function(){
var millisecondsInThisMonth = this.clone().endOfMonth().epoch() - this.clone().firstDayInCalendarMonth().epoch();
return Math.ceil(millisecondsInThisMonth / MILLISECONDS_IN_WEEK);
},
It might be a bit obscure since the meat of the functionality is in endOfMonth and firstDayInCalendarMonth, but you should at least be able to get some idea of how it works.

This works for me,
function(d){
var firstDay = new Date(this.getFullYear(), this.getMonth(), 1).getDay();
return Math.ceil((d.getDate() + (firstDay - 1))/7);
}
"d" should be the date.

A little rudimentary, yet should cater for original post :
/**
* #param {date} 2020-01-30
* #return {int} count
*/
this.numberOfCalendarWeekLines = date => {
// get total
let lastDayOfMonth = new Date( new Date( date ).getFullYear(), new Date( date ).getMonth() + 1, 0 );
let manyDaysInMonth = lastDayOfMonth.getDate();
// itterate through month - from 1st
// count calender week lines by occurance
// of a Saturday ( s m t w t f s )
let countCalendarWeekLines = 0;
for ( let i = 1; i <= manyDaysInMonth; i++ ) {
if ( new Date( new Date( date ).setDate( i ) ).getDay() === 6 ) countCalendarWeekLines++;
}
// days after last occurance of Saturday
// leaked onto new line?
if ( lastDayOfMonth.getDay() < 6 ) countCalendarWeekLines++;
return countCalendarWeekLines;
};

Thanks to Ed Poor for his solution, this is the same as Date prototype.
Date.prototype.countWeeksOfMonth = function() {
var year = this.getFullYear();
var month_number = this.getMonth();
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var used = firstOfMonth.getDay() + lastOfMonth.getDate();
return Math.ceil( used / 7);
}
So you can use it like
var weeksInCurrentMonth = new Date().countWeeksOfMonth();
var weeksInDecember2012 = new Date(2012,12,1).countWeeksOfMonth(); // 6

function getWeeksInMonth(month_number, year) {
console.log("year - "+year+" month - "+month_number+1);
var day = 0;
var firstOfMonth = new Date(year, month_number, 1);
var lastOfMonth = new Date(year, parseInt(month_number)+1, 0);
if (firstOfMonth.getDay() == 0) {
day = 2;
firstOfMonth = firstOfMonth.setDate(day);
firstOfMonth = new Date(firstOfMonth);
} else if (firstOfMonth.getDay() != 1) {
day = 9-(firstOfMonth.getDay());
firstOfMonth = firstOfMonth.setDate(day);
firstOfMonth = new Date(firstOfMonth);
}
var days = (lastOfMonth.getDate() - firstOfMonth.getDate())+1
return Math.ceil( days / 7);
}
It worked for me. Please try
Thanks all

This piece of code give you the exact number of weeks in a given month:
Date.prototype.getMonthWeek = function(monthAdjustement)
{
var firstDay = new Date(this.getFullYear(), this.getMonth(), 1).getDay();
var returnMessage = (Math.ceil(this.getDate()/7) + Math.floor(((7-firstDay)/7)));
return returnMessage;
}
The monthAdjustement variable adds or substract the month that you are currently in
I use it in a calendar project in JS and the equivalent in Objective-C and it works well

function weekCount(year, month_number, day_start) {
// month_number is in the range 1..12
// day_start is in the range 0..6 (where Sun=0, Mon=1, ... Sat=6)
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var dayOffset = (firstOfMonth.getDay() - day_start + 7) % 7;
var used = dayOffset + lastOfMonth.getDate();
return Math.ceil( used / 7);
}

I know this is coming late, I have seen codes upon codes trying to get the number of weeks a particular month falls on, but many have not been really precise but most have been really informative and reusable, I'm not an expert programmer but I can really think and thanks to some codes by some people I was able to arrive at a conclusion.
function convertDate(date) {//i lost the guy who owns this code lol
var yyyy = date.getFullYear().toString();
var mm = (date.getMonth()+1).toString();
var dd = date.getDate().toString();
var mmChars = mm.split('');
var ddChars = dd.split('');
return yyyy + '-' + (mmChars[1]?mm:"0"+mmChars[0]) + '-' + (ddChars[1]?dd:"0"+ddChars[0]);
}
//this line of code from https://stackoverflow.com/a/4028614/2540911
var days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'];
var myDate = new Date('2019-03-2');
//var myDate = new Date(); //or todays date
var c = convertDate(myDate).split("-");
let yr = c[0], mth = c[1], dy = c[2];
weekCount(yr, mth, dy)
//Ahh yes, this line of code is from Natim Up there, incredible work, https://stackoverflow.com/a/2485172/2540911
function weekCount(year, month_number, startDayOfWeek) {
// month_number is in the range 1..12
console.log(weekNumber);
// Get the first day of week week day (0: Sunday, 1: Monday, ...)
var firstDayOfWeek = startDayOfWeek || 0;
var firstOfMonth = new Date(year, month_number-1, 1);
var lastOfMonth = new Date(year, month_number, 0);
var numberOfDaysInMonth = lastOfMonth.getDate();
var first = firstOfMonth.getDate();
//initialize first week
let weekNumber = 1;
while(first-1 < numberOfDaysInMonth){
// add a day
firstOfMonth = firstOfMonth.setDate(firstOfMonth.getDate() + 1);//this line of code from https://stackoverflow.com/a/9989458/2540911
if(days[firstOfMonth.getDay()] === "Sunday"){//get new week every new sunday according the local date format
//get newWeek
weekNumber++;
}
if(weekNumber === 3 && days[firstOfMonth.getDay()] === "Friday")
alert(firstOfMonth);
first++
}
}
I needed this code to generate a schedule or event scheduler for a church on every 3rd friday of a new month, so you can modify this to suit your or just pick your specific date, not "friday and specify the week of the month and Voila!! here you go

None of the solutions here really worked for me. Here is my crack at it.
// Example
// weeksOfMonth(2019, 9) // October
// Result: 5
weeksOfMonth (year, monthIndex) {
const d = new Date(year, monthIndex+ 1, 0)
const adjustedDate = d.getDate() + d.getDay()
return Math.ceil(adjustedDate / 7)
}

Every solutions helped but nothing was working for me so I did my own with moment library :
const getWeeksInAMonth = (currentDate: string) => {
const startOfMonth = moment(currentDate).startOf("month")
const endOfMonth = moment(currentDate).endOf("month")
return moment(endOfMonth).week() - moment(startOfMonth).week() + 1
}