79 lines
2.7 KiB
JavaScript
79 lines
2.7 KiB
JavaScript
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import { constructFrom } from "./constructFrom.mjs";
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import { startOfWeek } from "./startOfWeek.mjs";
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import { toDate } from "./toDate.mjs";
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import { getDefaultOptions } from "./_lib/defaultOptions.mjs";
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/**
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* The {@link getWeekYear} function options.
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*/
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/**
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* @name getWeekYear
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* @category Week-Numbering Year Helpers
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* @summary Get the local week-numbering year of the given date.
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*
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* @description
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* Get the local week-numbering year of the given date.
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* The exact calculation depends on the values of
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* `options.weekStartsOn` (which is the index of the first day of the week)
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* and `options.firstWeekContainsDate` (which is the day of January, which is always in
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* the first week of the week-numbering year)
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*
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* Week numbering: https://en.wikipedia.org/wiki/Week#The_ISO_week_date_system
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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 given date
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* @param options - An object with options.
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*
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* @returns The local week-numbering year
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*
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* @example
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* // Which week numbering year is 26 December 2004 with the default settings?
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* const result = getWeekYear(new Date(2004, 11, 26))
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* //=> 2005
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*
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* @example
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* // Which week numbering year is 26 December 2004 if week starts on Saturday?
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* const result = getWeekYear(new Date(2004, 11, 26), { weekStartsOn: 6 })
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* //=> 2004
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*
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* @example
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* // Which week numbering year is 26 December 2004 if the first week contains 4 January?
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* const result = getWeekYear(new Date(2004, 11, 26), { firstWeekContainsDate: 4 })
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* //=> 2004
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*/
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export function getWeekYear(date, options) {
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const _date = toDate(date);
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const year = _date.getFullYear();
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const defaultOptions = getDefaultOptions();
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const firstWeekContainsDate =
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options?.firstWeekContainsDate ??
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options?.locale?.options?.firstWeekContainsDate ??
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defaultOptions.firstWeekContainsDate ??
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defaultOptions.locale?.options?.firstWeekContainsDate ??
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1;
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const firstWeekOfNextYear = constructFrom(date, 0);
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firstWeekOfNextYear.setFullYear(year + 1, 0, firstWeekContainsDate);
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firstWeekOfNextYear.setHours(0, 0, 0, 0);
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const startOfNextYear = startOfWeek(firstWeekOfNextYear, options);
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const firstWeekOfThisYear = constructFrom(date, 0);
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firstWeekOfThisYear.setFullYear(year, 0, firstWeekContainsDate);
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firstWeekOfThisYear.setHours(0, 0, 0, 0);
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const startOfThisYear = startOfWeek(firstWeekOfThisYear, options);
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if (_date.getTime() >= startOfNextYear.getTime()) {
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return year + 1;
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} else if (_date.getTime() >= startOfThisYear.getTime()) {
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return year;
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} else {
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return year - 1;
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}
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}
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// Fallback for modularized imports:
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export default getWeekYear;
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