date-fns/esm/getWeekYear/index.js

Modern JavaScript date utility library

import startOfWeek from "../startOfWeek/index.js";
import toDate from "../toDate/index.js";
import toInteger from "../_lib/toInteger/index.js";
import requiredArgs from "../_lib/requiredArgs/index.js";

/**
 * @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#Week_numbering
 *
 * ### 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).
 *
 * @param {Date|Number} date - the given date
 * @param {Object} [options] - an object with options.
 * @param {Locale} [options.locale=defaultLocale] - the locale object. See [Locale]{@link https://date-fns.org/docs/Locale}
 * @param {0|1|2|3|4|5|6} [options.weekStartsOn=0] - the index of the first day of the week (0 - Sunday)
 * @param {1|2|3|4|5|6|7} [options.firstWeekContainsDate=1] - the day of January, which is always in the first week of the year
 * @returns {Number} the local week-numbering year
 * @throws {TypeError} 1 argument required
 * @throws {RangeError} `options.weekStartsOn` must be between 0 and 6
 * @throws {RangeError} `options.firstWeekContainsDate` must be between 1 and 7
 *
 * @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 default function getWeekYear(dirtyDate, options) {
  var _options$locale, _options$locale$optio;

  requiredArgs(1, arguments);
  var date = toDate(dirtyDate);
  var year = date.getFullYear();
  var localeFirstWeekContainsDate = options === null || options === void 0 ? void 0 : (_options$locale = options.locale) === null || _options$locale === void 0 ? void 0 : (_options$locale$optio = _options$locale.options) === null || _options$locale$optio === void 0 ? void 0 : _options$locale$optio.firstWeekContainsDate;
  var defaultFirstWeekContainsDate = localeFirstWeekContainsDate == null ? 1 : toInteger(localeFirstWeekContainsDate);
  var firstWeekContainsDate = (options === null || options === void 0 ? void 0 : options.firstWeekContainsDate) == null ? defaultFirstWeekContainsDate : toInteger(options.firstWeekContainsDate); // Test if weekStartsOn is between 1 and 7 _and_ is not NaN

  if (!(firstWeekContainsDate >= 1 && firstWeekContainsDate <= 7)) {
    throw new RangeError('firstWeekContainsDate must be between 1 and 7 inclusively');
  }

  var firstWeekOfNextYear = new Date(0);
  firstWeekOfNextYear.setFullYear(year + 1, 0, firstWeekContainsDate);
  firstWeekOfNextYear.setHours(0, 0, 0, 0);
  var startOfNextYear = startOfWeek(firstWeekOfNextYear, options);
  var firstWeekOfThisYear = new Date(0);
  firstWeekOfThisYear.setFullYear(year, 0, firstWeekContainsDate);
  firstWeekOfThisYear.setHours(0, 0, 0, 0);
  var startOfThisYear = startOfWeek(firstWeekOfThisYear, options);

  if (date.getTime() >= startOfNextYear.getTime()) {
    return year + 1;
  } else if (date.getTime() >= startOfThisYear.getTime()) {
    return year;
  } else {
    return year - 1;
  }
}