Get Weeks In Month Through Javascript

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;};

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 );