date-fns/esm/_lib/getUTCWeekYear/index.js

Modern JavaScript date utility library

import toInteger from "../toInteger/index.js";
import toDate from "../../toDate/index.js";
import startOfUTCWeek from "../startOfUTCWeek/index.js";
import requiredArgs from "../requiredArgs/index.js"; // This function will be a part of public API when UTC function will be implemented.
// See issue: https://github.com/date-fns/date-fns/issues/376

export default function getUTCWeekYear(dirtyDate, dirtyOptions) {
  requiredArgs(1, arguments);
  var date = toDate(dirtyDate, dirtyOptions);
  var year = date.getUTCFullYear();
  var options = dirtyOptions || {};
  var locale = options.locale;
  var localeFirstWeekContainsDate = locale && locale.options && locale.options.firstWeekContainsDate;
  var defaultFirstWeekContainsDate = localeFirstWeekContainsDate == null ? 1 : toInteger(localeFirstWeekContainsDate);
  var firstWeekContainsDate = 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.setUTCFullYear(year + 1, 0, firstWeekContainsDate);
  firstWeekOfNextYear.setUTCHours(0, 0, 0, 0);
  var startOfNextYear = startOfUTCWeek(firstWeekOfNextYear, dirtyOptions);
  var firstWeekOfThisYear = new Date(0);
  firstWeekOfThisYear.setUTCFullYear(year, 0, firstWeekContainsDate);
  firstWeekOfThisYear.setUTCHours(0, 0, 0, 0);
  var startOfThisYear = startOfUTCWeek(firstWeekOfThisYear, dirtyOptions);

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