Calculate work days. filter holidates and weekend.

aviableDates.ts

const Holidays = require('date-holidays');
import * as moment from 'moment';

const holidays = new Holidays(process.env.LOCALE || 'ES');

// https://developer.mozilla.org/es/docs/Web/JavaScript/Referencia/Objetos_globales/Date/getDay
const weekendDays = [6, 0];
const isWeekEnd = (date: Date) => weekendDays.indexOf(date.getDay()) !== -1;

const filterAviableDates = (dates: Array<Date>) => {
  return dates.filter(date => {
    if (holidays.isHoliday(date)) {
      return false;
    }
    if (isWeekEnd(date)) {
      return false;
    }
    return true;
  });
};

const calculateAviableDates = (minimumDates: number) => (
  dates: Array<Date>,
  lastDateInit = null,
) => {
  let lastDate = lastDateInit || dates.slice(-1)[0];
  const datesFiltered = filterAviableDates(dates);
  if (datesFiltered.length === minimumDates) {
    return datesFiltered;
  } else {
    lastDate = moment(lastDate)
      .add(1, 'day')
      .toDate();
    return calculateAviableDates(minimumDates)(
      [...datesFiltered, lastDate],
      lastDate,
    );
  }
};

console.log(calculateAviableDates(3)([new Date('2019-02-22')]));
// [ 2019-02-22T00:00:00.000Z, 2019-02-25T00:00:00.000Z, 2019-02-26T00:00:00.000Z ]

aviableDatesSimple.ts

// simple implementation
const calculateAviableDates = (minimumDates: number) => (date: Date) => {
  const allYearDays = _.times(100).map(index =>
    moment(date)
      .add(index, 'day')
      .toDate(),
  );
  return _.take(filterAviableDates(allYearDays), minimumDates);
};