From d329cf4f02bf3a2db00a769c7836410b2e364079 Mon Sep 17 00:00:00 2001
From: Filipa Lacerda <filipa@gitlab.com>
Date: Mon, 11 Sep 2017 14:34:16 +0000
Subject: Adds Event polyfill for IE

---
 app/assets/javascripts/commons/polyfills.js            |  1 +
 .../javascripts/commons/polyfills/custom_event.js      |  7 ++++++-
 app/assets/javascripts/commons/polyfills/event.js      | 18 ++++++++++++++++++
 changelogs/unreleased/ie-event-polyfill.yml            |  5 +++++
 4 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 app/assets/javascripts/commons/polyfills/event.js
 create mode 100644 changelogs/unreleased/ie-event-polyfill.yml

diff --git a/app/assets/javascripts/commons/polyfills.js b/app/assets/javascripts/commons/polyfills.js
index b78089525cc..cb5a9a9f6b5 100644
--- a/app/assets/javascripts/commons/polyfills.js
+++ b/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';
diff --git a/app/assets/javascripts/commons/polyfills/custom_event.js b/app/assets/javascripts/commons/polyfills/custom_event.js
index aea61b82d03..db51ade61ae 100644
--- a/app/assets/javascripts/commons/polyfills/custom_event.js
+++ b/app/assets/javascripts/commons/polyfills/custom_event.js
@@ -1,7 +1,12 @@
 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;
   };
diff --git a/app/assets/javascripts/commons/polyfills/event.js b/app/assets/javascripts/commons/polyfills/event.js
new file mode 100644
index 00000000000..ff5b9a1982f
--- /dev/null
+++ b/app/assets/javascripts/commons/polyfills/event.js
@@ -0,0 +1,18 @@
+/**
+ * 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;
+}
diff --git a/changelogs/unreleased/ie-event-polyfill.yml b/changelogs/unreleased/ie-event-polyfill.yml
new file mode 100644
index 00000000000..eaab089a47e
--- /dev/null
+++ b/changelogs/unreleased/ie-event-polyfill.yml
@@ -0,0 +1,5 @@
+---
+title: Adds Event polyfill for IE11
+merge_request:
+author:
+type: fixed
-- 
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