fix: add CustomEvent polyfill for ie11

Author: mrholek

js/index.umd.js

@@ -5,6 +5,7 @@
  * --------------------------------------------------------------------------
  */
 
+import './src/polyfills'
 import AsyncLoad from './src/async-load'
 import Alert from './src/alert'
 import Button from './src/button'
@@ -19,7 +20,6 @@ import Sidebar from './src/sidebar'
 import Tab from './src/tab'
 import Toast from './src/toast'
 import Tooltip from './src/tooltip'
-import './src/polyfills'
 
 export default {
   AsyncLoad,

js/src/polyfills.js

@@ -498,3 +498,22 @@ if (!('Promise' in globalNS)) {
 }
 
 })));
+
+(function () {
+  if (
+      typeof window.CustomEvent === "function" ||
+      // In Safari, typeof CustomEvent == 'object' but it otherwise works fine
+      this.CustomEvent.toString().indexOf('CustomEventConstructor')>-1
+  ) { return; }
+
+  function CustomEvent ( event, params ) {
+    params = params || { bubbles: false, cancelable: false, detail: undefined };
+    var evt = document.createEvent( 'CustomEvent' );
+    evt.initCustomEvent( event, params.bubbles, params.cancelable, params.detail );
+    return evt;
+   }
+
+  CustomEvent.prototype = window.Event.prototype;
+
+  window.CustomEvent = CustomEvent;
+})();