From 7601c3765457a4ec7b2d48c0ca75fccf7fecf917 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <trueadm@users.noreply.github.com>
Date: Wed, 26 Sep 2018 13:38:56 +0100
Subject: [PATCH] Ensure "addEventListener" exists on "window" for "scheduler"
 package (#13731)

* Ensure addEventListener exists on "window"
---
 packages/scheduler/src/Scheduler.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/packages/scheduler/src/Scheduler.js b/packages/scheduler/src/Scheduler.js
index 412f96930e..2c692d7dfe 100644
--- a/packages/scheduler/src/Scheduler.js
+++ b/packages/scheduler/src/Scheduler.js
@@ -468,7 +468,12 @@ var requestHostCallback;
 var cancelHostCallback;
 var getFrameDeadline;
 
-if (typeof window === 'undefined') {
+// "addEventListener" might not be available on the window object
+// if this is a mocked "window" object. So we need to validate that too.
+if (
+  typeof window === 'undefined' ||
+  typeof window.addEventListener !== 'function'
+) {
   // If this accidentally gets imported in a non-browser environment, fallback
   // to a naive implementation.
   var timeoutID = -1;