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- import { addWeeks } from "./addWeeks.mjs";
- import { millisecondsInWeek } from "./constants.mjs";
- import { startOfISOWeekYear } from "./startOfISOWeekYear.mjs";
- /**
- * @name getISOWeeksInYear
- * @category ISO Week-Numbering Year Helpers
- * @summary Get the number of weeks in an ISO week-numbering year of the given date.
- *
- * @description
- * Get the number of weeks in an ISO week-numbering year of the given date.
- *
- * 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 given date
- *
- * @returns The number of ISO weeks in a year
- *
- * @example
- * // How many weeks are in ISO week-numbering year 2015?
- * const result = getISOWeeksInYear(new Date(2015, 1, 11))
- * //=> 53
- */
- export function getISOWeeksInYear(date) {
- const thisYear = startOfISOWeekYear(date);
- const nextYear = startOfISOWeekYear(addWeeks(thisYear, 60));
- const diff = +nextYear - +thisYear;
- // Round the number of weeks to the nearest integer because the number of
- // milliseconds in a week is not constant (e.g. it's different in the week of
- // the daylight saving time clock shift).
- return Math.round(diff / millisecondsInWeek);
- }
- // Fallback for modularized imports:
- export default getISOWeeksInYear;
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