Function getWeekYear

pkgs/core/src/getWeekYear/index.ts:57–89

(
  date: DateArg<Date> & {},
  options?: GetWeekYearOptions,
)

 * //=> 2004
 */
export function getWeekYear(
  date: DateArg<Date> & {},
  options?: GetWeekYearOptions,
): number {
  const _date = toDate(date, options?.in);
  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(options?.in || date, 0);
  firstWeekOfNextYear.setFullYear(year + 1, 0, firstWeekContainsDate);
  firstWeekOfNextYear.setHours(0, 0, 0, 0);
  const startOfNextYear = startOfWeek(firstWeekOfNextYear, options);

  const firstWeekOfThisYear = constructFrom(options?.in || date, 0);
  firstWeekOfThisYear.setFullYear(year, 0, firstWeekContainsDate);
  firstWeekOfThisYear.setHours(0, 0, 0, 0);
  const startOfThisYear = startOfWeek(firstWeekOfThisYear, options);

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