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Diffstat (limited to 'date-fns/src/lastDayOfISOWeekYear/index.ts')
-rw-r--r-- | date-fns/src/lastDayOfISOWeekYear/index.ts | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/date-fns/src/lastDayOfISOWeekYear/index.ts b/date-fns/src/lastDayOfISOWeekYear/index.ts new file mode 100644 index 0000000..425095f --- /dev/null +++ b/date-fns/src/lastDayOfISOWeekYear/index.ts @@ -0,0 +1,45 @@ +import getISOWeekYear from '../getISOWeekYear/index' +import startOfISOWeek from '../startOfISOWeek/index' +import requiredArgs from '../_lib/requiredArgs/index' + +/** + * @name lastDayOfISOWeekYear + * @category ISO Week-Numbering Year Helpers + * @summary Return the last day of an ISO week-numbering year for the given date. + * + * @description + * Return the last day 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 + * + * ### v2.0.0 breaking changes: + * + * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes). + * + * - The function was renamed from `lastDayOfISOYear` to `lastDayOfISOWeekYear`. + * "ISO week year" is short for [ISO week-numbering year](https://en.wikipedia.org/wiki/ISO_week_date). + * This change makes the name consistent with + * locale-dependent week-numbering year helpers, e.g., `getWeekYear`. + * + * @param {Date|Number} date - the original date + * @returns {Date} the end of an ISO week-numbering year + * @throws {TypeError} 1 argument required + * + * @example + * // The last day of an ISO week-numbering year for 2 July 2005: + * var result = lastDayOfISOWeekYear(new Date(2005, 6, 2)) + * //=> Sun Jan 01 2006 00:00:00 + */ +export default function lastDayOfISOWeekYear(dirtyDate: Date | number): Date { + requiredArgs(1, arguments) + + const year = getISOWeekYear(dirtyDate) + const fourthOfJanuary = new Date(0) + fourthOfJanuary.setFullYear(year + 1, 0, 4) + fourthOfJanuary.setHours(0, 0, 0, 0) + const date = startOfISOWeek(fourthOfJanuary) + date.setDate(date.getDate() - 1) + return date +} |