How to determine number Saturdays and Sundays comes between two dates in java script

Question

I have requirement as follows I have two dates i need to find how may saturdays and sundays will come in between
Date1: 02/06/2011
Date2: 02/07/2011
10 days are

Answer 1

O(1) solution with no loops:

function countWeekendDays( d0, d1 )
{
  var ndays = 1 + Math.round((d1.getTime()-d0.getTime())/(24*3600*1000));
  var nsaturdays = Math.floor( (d0.getDay()+ndays) / 7 );
  return 2*nsaturdays + (d0.getDay()==0) - (d1.getDay()==6);
}

jsFiddle