Get week of the month

Question

How can i get the week number of month using javascript / jquery?

For ex.:

First Week: 5th July, 2010. / Week Number = First monday

Previous Week: 12th July, 2010. / Week Number = Second monday

Current Date: 19th July, 2010. / Week Number = Third Monday

Next week: 26th July, 2010. / Week Number = Last monday

Answer 1

This is an old question, here is my cross-browser solution based on:

1. Weeks start on Sunday
2. The first week of a month is the one that contains the first of the month

So in March 2013:

• Fri 1 Mar is the first day of week 1
• Sun 3 Mar is the start of week 2
• Sun 31 Mar is the start of week 6 (and is the only day in the that week)
• Mon 1 Apr is the first day of week 1 in April.

    Date.prototype.getWeekOfMonth = function(exact) {         var month = this.getMonth()             , year = this.getFullYear()             , firstWeekday = new Date(year, month, 1).getDay()             , lastDateOfMonth = new Date(year, month + 1, 0).getDate()             , offsetDate = this.getDate() + firstWeekday - 1             , index = 1 // start index at 0 or 1, your choice             , weeksInMonth = index + Math.ceil((lastDateOfMonth + firstWeekday - 7) / 7)             , week = index + Math.floor(offsetDate / 7)         ;         if (exact || week < 2 + index) return week;         return week === weeksInMonth ? index + 5 : week;     };          // Simple helper to parse YYYY-MM-DD as local     function parseISOAsLocal(s){       var b = s.split(/\D/);       return new Date(b[0],b[1]-1,b[2]);     }      // Tests     console.log('Date          Exact|expected   not exact|expected');     [   ['2013-02-01', 1, 1],['2013-02-05', 2, 2],['2013-02-14', 3, 3],         ['2013-02-23', 4, 4],['2013-02-24', 5, 6],['2013-02-28', 5, 6],         ['2013-03-01', 1, 1],['2013-03-02', 1, 1],['2013-03-03', 2, 2],         ['2013-03-15', 3, 3],['2013-03-17', 4, 4],['2013-03-23', 4, 4],         ['2013-03-24', 5, 5],['2013-03-30', 5, 5],['2013-03-31', 6, 6],         ['2013-04-01', 1, 1]     ].forEach(function(test){       var d = parseISOAsLocal(test[0])       console.log(test[0] + '        ' +        d.getWeekOfMonth(true) + '|' + test[1] + '                  ' +       d.getWeekOfMonth() + '|' + test[2]);      });

You don't need to put it directly on the prototype if you don't want to. In my implementation, 6 means "Last", not "Sixth". If you want it to always return the actual week of the month, just pass true.

EDIT: Fixed this to handle 5 & 6-week months. My "unit tests", feel free to fork: http://jsfiddle.net/OlsonDev/5mXF6/1/.