Get Weeks In Month Through Javascript

Question

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 g

Answer 1

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