From 7aaf3616df5734bec62886faa6909b07a5d3c931 Mon Sep 17 00:00:00 2001
From: Samuel Clay <samuel@ofbrooklyn.com>
Date: Thu, 27 Jan 2011 11:38:06 -0500
Subject: [PATCH] Issue #107: Fixing issue with _.first([1,2,3], 0) returning
 first element instead of empty array.

---
 test/arrays.js | 2 ++
 underscore.js  | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/test/arrays.js b/test/arrays.js
index 7219c038e..e031afe9b 100644
--- a/test/arrays.js
+++ b/test/arrays.js
@@ -5,6 +5,7 @@ $(document).ready(function() {
   test("arrays: first", function() {
     equals(_.first([1,2,3]), 1, 'can pull out the first element of an array');
     equals(_([1, 2, 3]).first(), 1, 'can perform OO-style "first()"');
+    equals(_.first([1,2,3], 0).join(', '), "", 'can pass an index to first');
     equals(_.first([1,2,3], 2).join(', '), '1, 2', 'can pass an index to first');
     var result = (function(){ return _.first(arguments); })(4, 3, 2, 1);
     equals(result, 4, 'works on an arguments object.');
@@ -15,6 +16,7 @@ $(document).ready(function() {
   test("arrays: rest", function() {
     var numbers = [1, 2, 3, 4];
     equals(_.rest(numbers).join(", "), "2, 3, 4", 'working rest()');
+    equals(_.rest(numbers, 0).join(", "), "1, 2, 3, 4", 'working rest(0)');
     equals(_.rest(numbers, 2).join(', '), '3, 4', 'rest can take an index');
     var result = (function(){ return _(arguments).tail(); })(1, 2, 3, 4);
     equals(result.join(', '), '2, 3, 4', 'aliased as tail and works on arguments object');
diff --git a/underscore.js b/underscore.js
index 7c25ec41a..bd37e148b 100644
--- a/underscore.js
+++ b/underscore.js
@@ -284,7 +284,7 @@
   // values in the array. Aliased as `head`. The **guard** check allows it to work
   // with `_.map`.
   _.first = _.head = function(array, n, guard) {
-    return n && !guard ? slice.call(array, 0, n) : array[0];
+    return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
   };
 
   // Returns everything but the first entry of the array. Aliased as `tail`.
@@ -292,7 +292,7 @@
   // the rest of the values in the array from that index onward. The **guard**
   // check allows it to work with `_.map`.
   _.rest = _.tail = function(array, index, guard) {
-    return slice.call(array, _.isUndefined(index) || guard ? 1 : index);
+    return slice.call(array, (index == null) || guard ? 1 : index);
   };
 
   // Get the last element of an array.