From 2c58810bb2a1b2cea4f17f62c96fef3eb4b71602 Mon Sep 17 00:00:00 2001
From: Josh Fee <fenduru@users.noreply.github.com>
Date: Mon, 28 Aug 2017 13:56:52 -0400
Subject: [PATCH] perf(core): prevent iteration of arrays that should not be
 observable

close #6284
---
 src/core/observer/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/observer/index.js b/src/core/observer/index.js
index 9317dbbc47b..3dc10522dab 100644
--- a/src/core/observer/index.js
+++ b/src/core/observer/index.js
@@ -157,7 +157,7 @@ export function defineReactive (
         if (childOb) {
           childOb.dep.depend()
         }
-        if (Array.isArray(value)) {
+        if (Array.isArray(value) && Object.isExtensible(value)) {
           dependArray(value)
         }
       }