Issue #3278415 by nod_, lauriii, catch, Wim Leers, longwave, xjm, claudiu.cristea: Remove usages of the JavaScript ES6 build step, the build step itself, and associated dev dependencies

1 files changed, 53 insertions, 19 deletions

diff --git a/core/modules/system/js/system.js b/core/modules/system/js/system.js
index 86bbfb220a8b..7bca481c068b 100644
--- a/core/modules/system/js/system.js
+++ b/core/modules/system/js/system.js
@@ -1,24 +1,47 @@
 /**
-* DO NOT EDIT THIS FILE.
-* See the following change record for more information,
-* https://www.drupal.org/node/2815083
-* @preserve
-**/
+ * @file
+ * System behaviors.
+ */
 
 (function ($, Drupal, drupalSettings) {
+  // Cache IDs in an array for ease of use.
   const ids = [];
+
+  /**
+   * Attaches field copy behavior from input fields to other input fields.
+   *
+   * When a field is filled out, apply its value to other fields that will
+   * likely use the same value. In the installer this is used to populate the
+   * administrator email address with the same value as the site email address.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches the field copy behavior to an input field.
+   */
   Drupal.behaviors.copyFieldValue = {
     attach(context) {
-      Object.keys(drupalSettings.copyFieldValue || {}).forEach(element => {
+      // List of fields IDs on which to bind the event listener.
+      // Create an array of IDs to use with jQuery.
+      Object.keys(drupalSettings.copyFieldValue || {}).forEach((element) => {
         ids.push(element);
       });
 
       if (ids.length) {
-        $(once('copy-field-values', 'body')).on('value:copy', this.valueTargetCopyHandler);
-        $(once('copy-field-values', `#${ids.join(', #')}`)).on('blur', this.valueSourceBlurHandler);
+        // Listen to value:copy events on all dependent fields.
+        // We have to use body and not document because of the way jQuery events
+        // bubble up the DOM tree.
+        $(once('copy-field-values', 'body')).on(
+          'value:copy',
+          this.valueTargetCopyHandler,
+        );
+        // Listen on all source elements.
+        $(once('copy-field-values', `#${ids.join(', #')}`)).on(
+          'blur',
+          this.valueSourceBlurHandler,
+        );
       }
     },
-
     detach(context, settings, trigger) {
       if (trigger === 'unload' && ids.length) {
         $(once.remove('copy-field-values', 'body')).off('value:copy');
@@ -26,23 +49,34 @@
       }
     },
 
+    /**
+     * Event handler that fill the target element with the specified value.
+     *
+     * @param {jQuery.Event} e
+     *   Event object.
+     * @param {string} value
+     *   Custom value from jQuery trigger.
+     */
     valueTargetCopyHandler(e, value) {
-      const {
-        target
-      } = e;
-
+      const { target } = e;
       if (target.value === '') {
         target.value = value;
       }
     },
 
+    /**
+     * Handler for a Blur event on a source field.
+     *
+     * This event handler will trigger a 'value:copy' event on all dependent
+     * fields.
+     *
+     * @param {jQuery.Event} e
+     *   The event triggered.
+     */
     valueSourceBlurHandler(e) {
-      const {
-        value
-      } = e.target;
+      const { value } = e.target;
       const targetIds = drupalSettings.copyFieldValue[e.target.id];
       $(`#${targetIds.join(', #')}`).trigger('value:copy', value);
-    }
-
+    },
   };
-})(jQuery, Drupal, drupalSettings);
\ No newline at end of file
+})(jQuery, Drupal, drupalSettings);