38 lines
1.3 KiB
JavaScript
38 lines
1.3 KiB
JavaScript
|
import { getISOWeekYear } from "./getISOWeekYear.mjs";
|
||
|
|
import { startOfISOWeek } from "./startOfISOWeek.mjs";
|
||
|
|
import { constructFrom } from "./constructFrom.mjs";
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @name startOfISOWeekYear
|
||
|
|
* @category ISO Week-Numbering Year Helpers
|
||
|
|
* @summary Return the start of an ISO week-numbering year for the given date.
|
||
|
|
*
|
||
|
|
* @description
|
||
|
|
* Return the start of an ISO week-numbering year,
|
||
|
|
* which always starts 3 days before the year's first Thursday.
|
||
|
|
* The result will be in the local timezone.
|
||
|
|
*
|
||
|
|
* ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
|
||
|
|
*
|
||
|
|
* @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).
|
||
|
|
*
|
||
|
|
* @param date - The original date
|
||
|
|
*
|
||
|
|
* @returns The start of an ISO week-numbering year
|
||
|
|
*
|
||
|
|
* @example
|
||
|
|
* // The start of an ISO week-numbering year for 2 July 2005:
|
||
|
|
* const result = startOfISOWeekYear(new Date(2005, 6, 2))
|
||
|
|
* //=> Mon Jan 03 2005 00:00:00
|
||
|
|
*/
|
||
|
|
export function startOfISOWeekYear(date) {
|
||
|
|
const year = getISOWeekYear(date);
|
||
|
|
const fourthOfJanuary = constructFrom(date, 0);
|
||
|
|
fourthOfJanuary.setFullYear(year, 0, 4);
|
||
|
|
fourthOfJanuary.setHours(0, 0, 0, 0);
|
||
|
|
return startOfISOWeek(fourthOfJanuary);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Fallback for modularized imports:
|
||
|
|
export default startOfISOWeekYear;
|