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

Modern JavaScript date utility library

import toInteger from '../toInteger/index.js';
import toDate from '../../toDate/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 setUTCDay(dirtyDate, dirtyDay, dirtyOptions) {
  if (arguments.length < 2) {
    throw new TypeError('2 arguments required, but only ' + arguments.length + ' present');
  }

  var options = dirtyOptions || {};
  var locale = options.locale;
  var localeWeekStartsOn = locale && locale.options && locale.options.weekStartsOn;
  var defaultWeekStartsOn = localeWeekStartsOn == null ? 0 : toInteger(localeWeekStartsOn);
  var weekStartsOn = options.weekStartsOn == null ? defaultWeekStartsOn : toInteger(options.weekStartsOn); // Test if weekStartsOn is between 0 and 6 _and_ is not NaN

  if (!(weekStartsOn >= 0 && weekStartsOn <= 6)) {
    throw new RangeError('weekStartsOn must be between 0 and 6 inclusively');
  }

  var date = toDate(dirtyDate);
  var day = toInteger(dirtyDay);
  var currentDay = date.getUTCDay();
  var remainder = day % 7;
  var dayIndex = (remainder + 7) % 7;
  var diff = (dayIndex < weekStartsOn ? 7 : 0) + day - currentDay;
  date.setUTCDate(date.getUTCDate() + diff);
  return date;
}