65 lines
2.3 KiB
JavaScript
65 lines
2.3 KiB
JavaScript
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import { constructFrom } from "./constructFrom.mjs";
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import { getWeekYear } from "./getWeekYear.mjs";
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import { startOfWeek } from "./startOfWeek.mjs";
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import { getDefaultOptions } from "./_lib/defaultOptions.mjs";
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/**
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* The {@link startOfWeekYear} function options.
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*/
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/**
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* @name startOfWeekYear
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* @category Week-Numbering Year Helpers
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* @summary Return the start of a local week-numbering year for the given date.
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*
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* @description
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* Return the start of a local week-numbering year.
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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 original date
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* @param options - An object with options
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*
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* @returns The start of a week-numbering year
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*
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* @example
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* // The start of an a week-numbering year for 2 July 2005 with default settings:
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* const result = startOfWeekYear(new Date(2005, 6, 2))
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* //=> Sun Dec 26 2004 00:00:00
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*
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* @example
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* // The start of a week-numbering year for 2 July 2005
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* // if Monday is the first day of week
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* // and 4 January is always in the first week of the year:
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* const result = startOfWeekYear(new Date(2005, 6, 2), {
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* weekStartsOn: 1,
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* firstWeekContainsDate: 4
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* })
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* //=> Mon Jan 03 2005 00:00:00
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*/
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export function startOfWeekYear(date, options) {
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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 year = getWeekYear(date, options);
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const firstWeek = constructFrom(date, 0);
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firstWeek.setFullYear(year, 0, firstWeekContainsDate);
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firstWeek.setHours(0, 0, 0, 0);
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const _date = startOfWeek(firstWeek, options);
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return _date;
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}
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// Fallback for modularized imports:
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export default startOfWeekYear;
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