From 4b77b7a8b3b294577eaf8a4f5f33119c46506733 Mon Sep 17 00:00:00 2001
From: John-David Dalton <john.david.dalton@gmail.com>
Date: Sat, 19 Dec 2015 10:37:49 -0600
Subject: [PATCH] Make `_.add`, `_.subtract`, and `_.sum` not skip `NaN`
 values.

---
 lodash.js    | 10 +++++-----
 test/test.js | 18 ++++++++++++------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/lodash.js b/lodash.js
index 25d234ace..f40dfa9d2 100644
--- a/lodash.js
+++ b/lodash.js
@@ -835,7 +835,7 @@
 
     while (++index < length) {
       var current = iteratee(array[index]);
-      if (current === current && current != null) {
+      if (current !== undefined) {
         result = result === undefined ? current : (result + current);
       }
     }
@@ -13461,10 +13461,10 @@
      */
     function add(augend, addend) {
       var result;
-      if (augend === augend && augend != null) {
+      if (augend !== undefined) {
         result = augend;
       }
-      if (addend === addend && addend != null) {
+      if (addend !== undefined) {
         result = result === undefined ? addend : (result + addend);
       }
       return result;
@@ -13677,10 +13677,10 @@
      */
     function subtract(minuend, subtrahend) {
       var result;
-      if (minuend === minuend && minuend != null) {
+      if (minuend !== undefined) {
         result = minuend;
       }
-      if (subtrahend === subtrahend && subtrahend != null) {
+      if (subtrahend !== undefined) {
         result = result === undefined ? subtrahend : (result - subtrahend);
       }
       return result;
diff --git a/test/test.js b/test/test.js
index 062bee68a..f415c67df 100644
--- a/test/test.js
+++ b/test/test.js
@@ -17853,17 +17853,23 @@
       assert.deepEqual(actual, expected);
     });
 
+    QUnit.test('should skip `undefined` values', function(assert) {
+      assert.expect(1);
+
+      assert.strictEqual(_.sum([1, undefined]), 1);
+    });
+
+    QUnit.test('should not skip `NaN` values', function(assert) {
+      assert.expect(1);
+
+      assert.deepEqual(_.sum([1, NaN]), NaN);
+    });
+
     QUnit.test('should not coerce values to numbers', function(assert) {
       assert.expect(1);
 
       assert.strictEqual(_.sum(['1', '2']), '12');
     });
-
-    QUnit.test('should skip `null`, `undefined`, and `NaN` values', function(assert) {
-      assert.expect(1);
-
-      assert.strictEqual(_.sum(['1', null, undefined, NaN, '2']), '12');
-    });
   }());
 
   /*--------------------------------------------------------------------------*/