https://www.nssga.org/modules/composer/better_exposed_filters/js/bef_datepickers.js?tlkb8p

1/**
2 * @file
3 * bef_datepickers.js
4 *
5 * Provides jQueryUI Datepicker integration with Better Exposed Filters.
6 */
7
8(function ($, Drupal, drupalSettings) {
9  /*
10   * Helper functions
11   */
12  Drupal.behaviors.betterExposedFiltersDatePickers = {
13    attach: function (context, settings) {
14
15      const datepickers = document.querySelectorAll('.bef-datepicker');
16      datepickers.forEach(function (input) {
17        const defaultValue = input.getAttribute('default_value');
18
19        if (defaultValue) {
20          input.value = defaultValue;
21        }
22      });
23    }
24  };
25})(jQuery, Drupal, drupalSettings);