moment-biz/lib/add-subtract.js

Handle business days & weekends over multiple years

'use strict';

const moment = require('moment');

function addSubBuisnessDays(originalCall, direction, val, period, ...args) {
  if (val < 0)
    return this[direction === 'add' ? 'subtract' : 'add'](-val, period, ...args);

  const old = moment(this)[direction === 'add' ? 'startOf' : 'endOf']('day');

  // add week-ends
  const weekends = this.localeData()._config.weekends || [0, 6];
  const nbWeekends = Math.floor(val / (7 - weekends.length));
  originalCall.call(this, val + nbWeekends * weekends.length, 'day');

  // how many week-end days did we miss with the previous naive calculation?
  const weekendAdjustment = [...Array(val % (7 - weekends.length)).keys()].reduce(
    (acc, i) => acc + (weekends.indexOf((this.day() + (direction === 'add' ? -i + 7 : i)) % 7) >= 0),
    0
  );

  // adjust last weekend days if needed
  if (weekendAdjustment) {
    originalCall.call(this, weekendAdjustment, 'day');

    while (this.isWeekend())
      originalCall.call(this, 1, 'day');
  }

  // take holidays into account
  var dayBoundary = moment(this)[direction === 'add' ? 'endOf' : 'startOf']('day');

  const addSubIfHolidayÎsValid = date => {
    // if the holiday is not in the current period (or is on a weekend), ignore it
    if (!date.isValid() || date.isWeekend() ||
      direction === 'add' && (date <= old || date > dayBoundary) ||
      direction === 'subtract' && (date > old || date <= dayBoundary))
      return;
    this[direction](1, 'businessday');
    dayBoundary = moment(this)[direction === 'add' ? 'endOf' : 'startOf']('day');
  };

  for (let year = old.year(); year <= this.year(); ++year)
    moment.getHolidays(year, this.locale()).forEach(addSubIfHolidayÎsValid);

  return this;
}

const momentAdd = moment.fn.add;
moment.fn.add = function(val, period) {
  if (period !== 'businessday' && period !== 'businessdays')
    return momentAdd.call(this, ...arguments);

  return addSubBuisnessDays.call(this, momentAdd, 'add', ...arguments);
};

const momentSubtract = moment.fn.subtract;
moment.fn.subtract = function(val, period) {
  if (period !== 'businessday' && period !== 'businessdays')
    return momentSubtract.call(this, ...arguments);

  return addSubBuisnessDays.call(this, momentSubtract, 'subtract', ...arguments);
};