Prototype ¬ Detail

author: Ronald [+], Submitted: 08.24.06 1p

Date.prototype.getWeekNr=function()
{
  var ms1d = 864e5; 
  var ms7d = 6048e5;
  var DC3 = Date.UTC(this.getFullYear(), this.getMonth(), this.getDate()+3)/ms1d;
  var DoW = 1 + (DC3+7777777)%7;
  var AWN = Math.floor(DC3/7); 
  var Wyr = new Date(AWN*ms7d).getUTCFullYear();
  return(AWN - Math.floor(Date.UTC(Wyr, 0, 0)/ms7d));
};

usage

var weekNr = new Date().getWeekNr() // get today's week number