42 lines
1.5 KiB
JavaScript
42 lines
1.5 KiB
JavaScript
import { constructFrom } from "./constructFrom.mjs";
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import { differenceInCalendarDays } from "./differenceInCalendarDays.mjs";
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import { startOfISOWeekYear } from "./startOfISOWeekYear.mjs";
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import { toDate } from "./toDate.mjs";
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/**
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* @name setISOWeekYear
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* @category ISO Week-Numbering Year Helpers
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* @summary Set the ISO week-numbering year to the given date.
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*
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* @description
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* Set the ISO week-numbering year to the given date,
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* saving the week number and the weekday number.
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*
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* ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
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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 weekYear - The ISO week-numbering year of the new date
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*
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* @returns The new date with the ISO week-numbering year set
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*
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* @example
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* // Set ISO week-numbering year 2007 to 29 December 2008:
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* const result = setISOWeekYear(new Date(2008, 11, 29), 2007)
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* //=> Mon Jan 01 2007 00:00:00
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*/
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export function setISOWeekYear(date, weekYear) {
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let _date = toDate(date);
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const diff = differenceInCalendarDays(_date, startOfISOWeekYear(_date));
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const fourthOfJanuary = constructFrom(date, 0);
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fourthOfJanuary.setFullYear(weekYear, 0, 4);
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fourthOfJanuary.setHours(0, 0, 0, 0);
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_date = startOfISOWeekYear(fourthOfJanuary);
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_date.setDate(_date.getDate() + diff);
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return _date;
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}
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// Fallback for modularized imports:
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export default setISOWeekYear;
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