📝 Commit Details:

backend/node_modules/date-fns/getWeekYear.js

@@ -0,0 +1,76 @@
+import { getDefaultOptions } from "./_lib/defaultOptions.js";
+import { constructFrom } from "./constructFrom.js";
+import { startOfWeek } from "./startOfWeek.js";
+import { toDate } from "./toDate.js";
+
+/**
+ * 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
+ *
+ * @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, 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;
+  }
+}
+
+// Fallback for modularized imports:
+export default getWeekYear;