Function startOfISOWeekYear

pkgs/core/src/startOfISOWeekYear/index.ts:38–50

(
  date: DateArg<DateType>,
  options?: StartOfISOWeekYearOptions<ResultDate> | undefined,
)

 * //=> Mon Jan 03 2005 00:00:00
 */
export function startOfISOWeekYear<
  DateType extends Date,
  ResultDate extends Date = DateType,
>(
  date: DateArg<DateType>,
  options?: StartOfISOWeekYearOptions<ResultDate> | undefined,
): ResultDate {
  const year = getISOWeekYear(date, options);
  const fourthOfJanuary = constructFrom(options?.in || date, 0);
  fourthOfJanuary.setFullYear(year, 0, 4);
  fourthOfJanuary.setHours(0, 0, 0, 0);
  return startOfISOWeek(fourthOfJanuary);
}