66 lines
2.3 KiB
JavaScript
66 lines
2.3 KiB
JavaScript
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import { constructFrom } from "./constructFrom.mjs";
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import { isSaturday } from "./isSaturday.mjs";
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import { isSunday } from "./isSunday.mjs";
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import { isWeekend } from "./isWeekend.mjs";
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import { toDate } from "./toDate.mjs";
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/**
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* @name addBusinessDays
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* @category Date Extension Helpers
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* @summary Add the specified number of business days (mon - fri) to the given date.
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*
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* @description
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* Add the specified number of business days (mon - fri) to the given date, ignoring weekends.
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*
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* @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
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*
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* @param date - The date to be changed
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* @param amount - The amount of business days to be added.
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*
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* @returns The new date with the business days added
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*
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* @example
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* // Add 10 business days to 1 September 2014:
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* const result = addBusinessDays(new Date(2014, 8, 1), 10)
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* //=> Mon Sep 15 2014 00:00:00 (skipped weekend days)
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*/
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export function addBusinessDays(date, amount) {
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const _date = toDate(date);
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const startedOnWeekend = isWeekend(_date);
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if (isNaN(amount)) return constructFrom(date, NaN);
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const hours = _date.getHours();
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const sign = amount < 0 ? -1 : 1;
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const fullWeeks = Math.trunc(amount / 5);
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_date.setDate(_date.getDate() + fullWeeks * 7);
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// Get remaining days not part of a full week
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let restDays = Math.abs(amount % 5);
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// Loops over remaining days
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while (restDays > 0) {
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_date.setDate(_date.getDate() + sign);
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if (!isWeekend(_date)) restDays -= 1;
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}
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// If the date is a weekend day and we reduce a dividable of
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// 5 from it, we land on a weekend date.
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// To counter this, we add days accordingly to land on the next business day
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if (startedOnWeekend && isWeekend(_date) && amount !== 0) {
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// If we're reducing days, we want to add days until we land on a weekday
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// If we're adding days we want to reduce days until we land on a weekday
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if (isSaturday(_date)) _date.setDate(_date.getDate() + (sign < 0 ? 2 : -1));
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if (isSunday(_date)) _date.setDate(_date.getDate() + (sign < 0 ? 1 : -2));
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}
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// Restore hours to avoid DST lag
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_date.setHours(hours);
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return _date;
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}
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// Fallback for modularized imports:
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export default addBusinessDays;
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