Adds Event polyfill for IE

app/assets/javascripts/commons/polyfills.js

@@ -12,4 +12,5 @@ import 'core-js/fn/symbol';
 // Browser polyfills
 import './polyfills/custom_event';
 import './polyfills/element';
+import './polyfills/event';
 import './polyfills/nodelist';

app/assets/javascripts/commons/polyfills/custom_event.js

 if (typeof window.CustomEvent !== 'function') {
   window.CustomEvent = function CustomEvent(event, params) {
     const evt = document.createEvent('CustomEvent');
-    const evtParams = params || { bubbles: false, cancelable: false, detail: undefined };
+    const evtParams = {
+      bubbles: false,
+      cancelable: false,
+      detail: undefined,
+      ...params,
+    };
     evt.initCustomEvent(event, evtParams.bubbles, evtParams.cancelable, evtParams.detail);
     return evt;
   };

app/assets/javascripts/commons/polyfills/event.js

+/**
+ * Polyfill for IE11 support.
+ * new Event() is not supported by IE11.
+ * Although `initEvent` is deprecated for modern browsers it is the one supported by IE
+ */
+if (typeof window.Event !== 'function') {
+  window.Event = function Event(event, params) {
+    const evt = document.createEvent('Event');
+    const evtParams = {
+      bubbles: false,
+      cancelable: false,
+      ...params,
+    };
+    evt.initEvent(event, evtParams.bubbles, evtParams.cancelable);
+    return evt;
+  };
+  window.Event.prototype = Event;
+}

changelogs/unreleased/ie-event-polyfill.yml

+---
+title: Adds Event polyfill for IE11
+merge_request:
+author:
+type: fixed