https://www.intimina.com/core/modules/system/js/system.js?v=10.2.3

1/**
2 * @file
3 * System behaviors.
4 */
5
6(function ($, Drupal, drupalSettings) {
7  // Cache IDs in an array for ease of use.
8  const ids = [];
9
10  /**
11   * Attaches field copy behavior from input fields to other input fields.
12   *
13   * When a field is filled out, apply its value to other fields that will
14   * likely use the same value. In the installer this is used to populate the
15   * administrator email address with the same value as the site email address.
16   *
17   * @type {Drupal~behavior}
18   *
19   * @prop {Drupal~behaviorAttach} attach
20   *   Attaches the field copy behavior to an input field.
21   */
22  Drupal.behaviors.copyFieldValue = {
23    attach(context) {
24      // List of fields IDs on which to bind the event listener.
25      // Create an array of IDs to use with jQuery.
26      Object.keys(drupalSettings.copyFieldValue || {}).forEach((element) => {
27        ids.push(element);
28      });
29
30      if (ids.length) {
31        // Listen to value:copy events on all dependent fields.
32        // We have to use body and not document because of the way jQuery events
33        // bubble up the DOM tree.
34        $(once('copy-field-values', 'body')).on(
35          'value:copy',
36          this.valueTargetCopyHandler,
37        );
38        // Listen on all source elements.
39        $(once('copy-field-values', `#${ids.join(', #')}`)).on(
40          'blur',
41          this.valueSourceBlurHandler,
42        );
43      }
44    },
45    detach(context, settings, trigger) {
46      if (trigger === 'unload' && ids.length) {
47        $(once.remove('copy-field-values', 'body')).off('value:copy');
48        $(once.remove('copy-field-values', `#${ids.join(', #')}`)).off('blur');
49      }
50    },
51
52    /**
53     * Event handler that fill the target element with the specified value.
54     *
55     * @param {jQuery.Event} e
56     *   Event object.
57     * @param {string} value
58     *   Custom value from jQuery trigger.
59     */
60    valueTargetCopyHandler(e, value) {
61      const { target } = e;
62      if (target.value === '') {
63        target.value = value;
64      }
65    },
66
67    /**
68     * Handler for a Blur event on a source field.
69     *
70     * This event handler will trigger a 'value:copy' event on all dependent
71     * fields.
72     *
73     * @param {jQuery.Event} e
74     *   The event triggered.
75     */
76    valueSourceBlurHandler(e) {
77      const { value } = e.target;
78      const targetIds = drupalSettings.copyFieldValue[e.target.id];
79      $(`#${targetIds.join(', #')}`).trigger('value:copy', value);
80    },
81  };
82})(jQuery, Drupal, drupalSettings);