From 4bd0a40037526b2f2e639abc499aae1c15780542 Mon Sep 17 00:00:00 2001
From: Ben Alpert <spicyjalapeno@gmail.com>
Date: Sun, 24 Nov 2013 01:33:28 -0500
Subject: [PATCH] Don't use .returnValue if .defaultPrevented exists

`.defaultPrevented` exists in IE9+. I checked in IE9, Chrome, and Firefox that it does default to `false`.

Fixes #527.
---
 src/event/synthetic/SyntheticEvent.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/event/synthetic/SyntheticEvent.js b/src/event/synthetic/SyntheticEvent.js
index efd849edc4de6..8fb409a9dd99f 100644
--- a/src/event/synthetic/SyntheticEvent.js
+++ b/src/event/synthetic/SyntheticEvent.js
@@ -79,7 +79,10 @@ function SyntheticEvent(dispatchConfig, dispatchMarker, nativeEvent) {
     }
   }
 
-  if (nativeEvent.defaultPrevented || nativeEvent.returnValue === false) {
+  var defaultPrevented = nativeEvent.defaultPrevented != null ?
+    nativeEvent.defaultPrevented :
+    nativeEvent.returnValue === false;
+  if (defaultPrevented) {
     this.isDefaultPrevented = emptyFunction.thatReturnsTrue;
   } else {
     this.isDefaultPrevented = emptyFunction.thatReturnsFalse;