Calculate previous working day excluding weekends and federal holidays in JavaScript

Question

I am writing a function which will provide me previous working day for any given date. Working day means it is a weekday and there\'s no federal holiday on that day.

My

Answer 1

You are not using Luxon to its full potential. You should leave the date as a Luxon object, do all the operations on it using Luxon's methods, and then convert the date into a string.

To do that, I defined a helper function prevBusinessDayHelper that takes a Luxon datetime and returns a date time representing the previous business day. It operates entirely in terms of Luxon datetimes, which makes it easy. Then in the outer function, I convert to and from Luxon datetimes.

const DateTime = luxon.DateTime;

// use a Set to make lookups cheaper
const federalHolidays = new Set([
  '2019-05-27', // <-- you were missing the 0 here in yours
  '2019-09-02',
  // snip
]);

// recursion is good here because it's very shallow
const prevBusinessDayHelper = dt => {

  // use luxon's tools!
  const yest = dt.minus({ days: 1 });

  if (yest.weekday == 6 || yest.weekday == 7 || federalHolidays.has(yest.toISODate()))
    return prevBusinessDayHelper(yest);

  return yest;
};

const prevBusinessDay = (isoString, zone) => {
  const dt = DateTime.fromISO(isoString).setZone(zone);
  return prevBusinessDayHelper(dt).toISODate();
};

console.log(prevBusinessDay("2019-05-28T07:00:00.000Z", "America/New_York"));