From 98c422d227fb9110cc4971f545c7d0e96dc66c03 Mon Sep 17 00:00:00 2001
From: John-David Dalton <john.david.dalton@gmail.com>
Date: Tue, 24 May 2016 09:43:00 -0700
Subject: [PATCH] Avoid inspecting the entire key-value array when adding
 values to a stack.

---
 lodash.js | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lodash.js b/lodash.js
index ed59da8ba..fb68399b2 100644
--- a/lodash.js
+++ b/lodash.js
@@ -2122,8 +2122,13 @@
      */
     function stackSet(key, value) {
       var cache = this.__data__;
-      if (Map && cache instanceof ListCache && cache.__data__.length == LARGE_ARRAY_SIZE) {
-        cache = this.__data__ = new MapCache(cache.__data__);
+      if (cache instanceof ListCache) {
+        var pairs = cache.__data__;
+        if (!Map || pairs.length < LARGE_ARRAY_SIZE) {
+          pairs.push([key, value]);
+          return this;
+        }
+        cache = this.__data__ = new MapCache(pairs);
       }
       cache.set(key, value);
       return this;