Calculate an expected delivery date (accounting for holidays) in business days using JavaScript?

Question

After revisiting this script, and some modifications, the following is available to allow a user to add a feature that calculates the expected delivery date.

Answer 1

I've adapted Mark Giblin's revised code to better deal with end of year dates and also U.S. federal holidays. See below...

function businessDaysFromDate(date,businessDays) {
  var counter = 0, tmp = new Date(date);
  while( businessDays>=0 ) {
    tmp.setTime( date.getTime() + counter * 86400000 );
    if(isBusinessDay (tmp)) {
      --businessDays;
    }
    ++counter;
  }
  return tmp;
}

function isBusinessDay (date) {
  var dayOfWeek = date.getDay();
  if(dayOfWeek === 0 || dayOfWeek === 6) {
    // Weekend
    return false;
  }

  holidays = [
    '12/31+5', // New Year's Day on a saturday celebrated on previous friday
    '1/1',     // New Year's Day
    '1/2+1',   // New Year's Day on a sunday celebrated on next monday
    '1-3/1',   // Birthday of Martin Luther King, third Monday in January
    '2-3/1',   // Washington's Birthday, third Monday in February
    '5~1/1',   // Memorial Day, last Monday in May
    '7/3+5',   // Independence Day
    '7/4',     // Independence Day
    '7/5+1',   // Independence Day
    '9-1/1',   // Labor Day, first Monday in September
    '10-2/1',  // Columbus Day, second Monday in October
    '11/10+5', // Veterans Day
    '11/11',   // Veterans Day
    '11/12+1', // Veterans Day
    '11-4/4',  // Thanksgiving Day, fourth Thursday in November
    '12/24+5', // Christmas Day
    '12/25',   // Christmas Day
    '12/26+1',  // Christmas Day
  ];

  var dayOfMonth = date.getDate(),
  month = date.getMonth() + 1,
  monthDay = month + '/' + dayOfMonth;

  if(holidays.indexOf(monthDay)>-1){
    return false;
  }

  var monthDayDay = monthDay + '+' + dayOfWeek;
  if(holidays.indexOf(monthDayDay)>-1){
    return false;
  }

  var weekOfMonth = Math.floor((dayOfMonth - 1) / 7) + 1,
      monthWeekDay = month + '-' + weekOfMonth + '/' + dayOfWeek;
  if(holidays.indexOf(monthWeekDay)>-1){
    return false;
  }

  var lastDayOfMonth = new Date(date);
  lastDayOfMonth.setMonth(lastDayOfMonth.getMonth() + 1);
  lastDayOfMonth.setDate(0);
  var negWeekOfMonth = Math.floor((lastDayOfMonth.getDate() - dayOfMonth - 1) / 7) + 1,
      monthNegWeekDay = month + '~' + negWeekOfMonth + '/' + dayOfWeek;
  if(holidays.indexOf(monthNegWeekDay)>-1){
    return false;
  }

  return true;
}