From 3f8dd7e658bf2b17bf7ca3b3c0f084ef9159f46e Mon Sep 17 00:00:00 2001
From: John-David Dalton <john.david.dalton@gmail.com>
Date: Sat, 27 Dec 2014 23:09:56 -0600
Subject: [PATCH] Add test for `customizer` results of `NaN`.

---
 lodash.js    | 8 +++++---
 test/test.js | 4 ++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/lodash.js b/lodash.js
index 3be6d1dcf..95d844a6c 100644
--- a/lodash.js
+++ b/lodash.js
@@ -1695,7 +1695,8 @@
           var value = object[key],
               result = customizer(value, source[key], key, object, source);
 
-          if (result !== value || (typeof value == 'undefined' && !(key in object))) {
+          if ((result === result ? result !== value : value === value) ||
+              (typeof value == 'undefined' && !(key in object))) {
             object[key] = result;
           }
         } else {
@@ -2496,7 +2497,8 @@
           if (isCommon) {
             result = srcValue;
           }
-          if ((isSrcArr || typeof result != 'undefined') && (isCommon || result !== value)) {
+          if ((isSrcArr || typeof result != 'undefined') &&
+              (isCommon || (result === result ? result !== value : value === value))) {
             object[key] = result;
           }
           return;
@@ -2528,7 +2530,7 @@
         // Recursively merge objects and arrays (susceptible to call stack limits).
         if (isCommon) {
           object[key] = baseMerge(result, srcValue, customizer, stackA, stackB);
-        } else if (result !== value) {
+        } else if (result === result ? result !== value : value === value) {
           object[key] = result;
         }
       });
diff --git a/test/test.js b/test/test.js
index 471113d53..317540080 100644
--- a/test/test.js
+++ b/test/test.js
@@ -4796,8 +4796,8 @@
       deepEqual(actual, { 'a': 1, 'b': 2, 'c': 3 });
     });
 
-    test('`_.' + methodName + '` should not assign the `customizer` result if it is the same as the destination value', 3, function() {
-      _.each(['a', ['a'], { 'a': 1 }], function(value) {
+    test('`_.' + methodName + '` should not assign the `customizer` result if it is the same as the destination value', 4, function() {
+      _.each(['a', ['a'], { 'a': 1 }, NaN], function(value) {
         if (defineProperty) {
           var object = {},
               pass = true;