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 王天杨
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import { constructFrom } from "./constructFrom.mjs";
import { startOfWeek } from "./startOfWeek.mjs";
import { toDate } from "./toDate.mjs";
import { getDefaultOptions } from "./_lib/defaultOptions.mjs";
/**
* The {@link getWeekYear} function options.
*/
/**
* @name getWeekYear
* @category Week-Numbering Year Helpers
* @summary Get the local week-numbering year of the given date.
*
* @description
* Get the local week-numbering year of the given date.
* The exact calculation depends on the values of
* `options.weekStartsOn` (which is the index of the first day of the week)
* and `options.firstWeekContainsDate` (which is the day of January, which is always in
* the first week of the week-numbering year)
*
* Week numbering: https://en.wikipedia.org/wiki/Week#The_ISO_week_date_system
*
* @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
* @param options - An object with options.
*
* @returns The local week-numbering year
*
* @example
* // Which week numbering year is 26 December 2004 with the default settings?
* const result = getWeekYear(new Date(2004, 11, 26))
* //=> 2005
*
* @example
* // Which week numbering year is 26 December 2004 if week starts on Saturday?
* const result = getWeekYear(new Date(2004, 11, 26), { weekStartsOn: 6 })
* //=> 2004
*
* @example
* // Which week numbering year is 26 December 2004 if the first week contains 4 January?
* const result = getWeekYear(new Date(2004, 11, 26), { firstWeekContainsDate: 4 })
* //=> 2004
*/
export function getWeekYear(date, options) {
const _date = toDate(date);
const year = _date.getFullYear();
const defaultOptions = getDefaultOptions();
const firstWeekContainsDate =
options?.firstWeekContainsDate ??
options?.locale?.options?.firstWeekContainsDate ??
defaultOptions.firstWeekContainsDate ??
defaultOptions.locale?.options?.firstWeekContainsDate ??
1;
const firstWeekOfNextYear = constructFrom(date, 0);
firstWeekOfNextYear.setFullYear(year + 1, 0, firstWeekContainsDate);
firstWeekOfNextYear.setHours(0, 0, 0, 0);
const startOfNextYear = startOfWeek(firstWeekOfNextYear, options);
const firstWeekOfThisYear = constructFrom(date, 0);
firstWeekOfThisYear.setFullYear(year, 0, firstWeekContainsDate);
firstWeekOfThisYear.setHours(0, 0, 0, 0);
const startOfThisYear = startOfWeek(firstWeekOfThisYear, options);
if (_date.getTime() >= startOfNextYear.getTime()) {
return year + 1;
} else if (_date.getTime() >= startOfThisYear.getTime()) {
return year;
} else {
return year - 1;
}
}
// Fallback for modularized imports:
export default getWeekYear;
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