Issue #3096516 by narendra.rajwar27, nod_, Charlie ChX Negyesi: domready has a race condition

core/misc/drupal.init.es6.js

@@ -16,13 +16,13 @@ document.documentElement.className += ' js';
    *   The function to be called on document ready.
    */
   const domReady = callback => {
+    const listener = () => {
+      callback();
+      document.removeEventListener('DOMContentLoaded', listener);
+    };
     if (document.readyState !== 'loading') {
       callback();
     } else {
-      const listener = () => {
-        callback();
-        document.removeEventListener('DOMContentLoaded', listener);
-      };
       document.addEventListener('DOMContentLoaded', listener);
     }
   };

core/misc/drupal.init.js

@@ -13,14 +13,14 @@ document.documentElement.className += ' js';
 
 (function (Drupal, drupalSettings) {
   var domReady = function domReady(callback) {
+    var listener = function listener() {
+      callback();
+      document.removeEventListener('DOMContentLoaded', listener);
+    };
+
     if (document.readyState !== 'loading') {
       callback();
     } else {
-      var listener = function listener() {
-        callback();
-        document.removeEventListener('DOMContentLoaded', listener);
-      };
-
       document.addEventListener('DOMContentLoaded', listener);
     }
   };