From 5c00abcf8786974ece0d6d01cfb4ba9740fa05a4 Mon Sep 17 00:00:00 2001
From: Jan Raasch <janraasch@gmail.com>
Date: Tue, 15 Nov 2011 22:46:18 +0100
Subject: [PATCH 1/2] Provided _.indexOf and _.lastIndexOf with proper sparse
 array support.

---
 underscore.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/underscore.js b/underscore.js
index 5579c07d3..467f4ef8f 100644
--- a/underscore.js
+++ b/underscore.js
@@ -432,7 +432,7 @@
       return array[i] === item ? i : -1;
     }
     if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
-    for (i = 0, l = array.length; i < l; i++) if (array[i] === item) return i;
+    for (i = 0, l = array.length; i < l; i++) if (!_.isUndefined(array[i]) && array[i] === item) return i;
     return -1;
   };
 
@@ -441,7 +441,7 @@
     if (array == null) return -1;
     if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
     var i = array.length;
-    while (i--) if (array[i] === item) return i;
+    while (i--) if (!_.isUndefined(array[i]) && array[i] === item) return i;
     return -1;
   };
 

From bf7a351fd6048f096ce2de6b6a2d486c496d940c Mon Sep 17 00:00:00 2001
From: Jan Raasch <janraasch@gmail.com>
Date: Tue, 15 Nov 2011 23:55:04 +0100
Subject: [PATCH 2/2] (Actually) Provided _.indexOf and _.lastIndexOf with
 proper sparse array support.

---
 underscore.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/underscore.js b/underscore.js
index 467f4ef8f..821084409 100644
--- a/underscore.js
+++ b/underscore.js
@@ -432,7 +432,7 @@
       return array[i] === item ? i : -1;
     }
     if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item);
-    for (i = 0, l = array.length; i < l; i++) if (!_.isUndefined(array[i]) && array[i] === item) return i;
+    for (i = 0, l = array.length; i < l; i++) if (i in array && array[i] === item) return i;
     return -1;
   };
 
@@ -441,7 +441,7 @@
     if (array == null) return -1;
     if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) return array.lastIndexOf(item);
     var i = array.length;
-    while (i--) if (!_.isUndefined(array[i]) && array[i] === item) return i;
+    while (i--) if (i in array && array[i] === item) return i;
     return -1;
   };