diff -u b/core/misc/ajax.es6.js b/core/misc/ajax.es6.js
--- b/core/misc/ajax.es6.js
+++ b/core/misc/ajax.es6.js
@@ -40,7 +40,7 @@
       }
 
       // Load all Ajax behaviors specified in the settings.
-      Object.keys(settings.ajax).forEach(loadAjaxBehavior);
+      Object.keys(settings.ajax || {}).forEach(loadAjaxBehavior);
 
       Drupal.ajax.bindAjaxLinks(document.body);
 
@@ -1352,2 +1352,3 @@
   };
+
 }(jQuery, window, Drupal, drupalSettings));
diff -u b/core/misc/ajax.js b/core/misc/ajax.js
--- b/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -21,7 +21,7 @@
         });
       }
 
-      Object.keys(settings.ajax).forEach(loadAjaxBehavior);
+      Object.keys(settings.ajax || {}).forEach(loadAjaxBehavior);
 
       Drupal.ajax.bindAjaxLinks(document.body);
 
diff -u b/core/misc/drupal.es6.js b/core/misc/drupal.es6.js
--- b/core/misc/drupal.es6.js
+++ b/core/misc/drupal.es6.js
@@ -315,7 +315,7 @@
     // If the array of keys is not passed then collect the keys from the args.
     if (!Array.isArray(keys)) {
       keys = [];
-      Object.keys(args).forEach(keys.push);
+      Object.keys(args).forEach(key => keys.push(key));
 
       // Order the keys by the character length. The shortest one is the first.
       keys.sort((a, b) => a.length - b.length);
diff -u b/core/misc/drupal.js b/core/misc/drupal.js
--- b/core/misc/drupal.js
+++ b/core/misc/drupal.js
@@ -81,7 +81,9 @@
 
     if (!Array.isArray(keys)) {
       keys = [];
-      Object.keys(args).forEach(keys.push);
+      Object.keys(args).forEach(function (key) {
+        return keys.push(key);
+      });
 
       keys.sort(function (a, b) {
         return a.length - b.length;
reverted:
--- b/core/modules/contextual/js/contextual.es6.js
+++ a/core/modules/contextual/js/contextual.es6.js
@@ -263,4 +263,5 @@
   $(document).on('drupalContextualLinkAdded', (event, data) => {
     Drupal.ajax.bindAjaxLinks(data.$el[0]);
   });
+
 }(jQuery, Drupal, drupalSettings, _, Backbone, window.JSON, window.sessionStorage));
diff -u b/core/modules/editor/js/editor.admin.es6.js b/core/modules/editor/js/editor.admin.es6.js
--- b/core/modules/editor/js/editor.admin.es6.js
+++ b/core/modules/editor/js/editor.admin.es6.js
@@ -569,7 +569,7 @@
       Drupal.filterConfiguration.update();
       Object.keys(Drupal.filterConfiguration.statuses).some((filterID) => {
         const filterStatus = Drupal.filterConfiguration.statuses[filterID];
-        return !filterStatusAllowsFeature(filterStatus, feature)
+        return !filterStatusAllowsFeature(filterStatus, feature);
       });
 
       return true;