From 9b1da9b2581ecfe549abeb443f81e4feca76bbbc Mon Sep 17 00:00:00 2001
From: Jeremy Ashkenas <jashkenas@gmail.com>
Date: Thu, 29 Oct 2009 11:03:53 -0400
Subject: [PATCH] optimized keys, values, and pluck

---
 index.html    |  4 ++--
 underscore.js | 16 ++++------------
 2 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/index.html b/index.html
index 33716be85..883780995 100644
--- a/index.html
+++ b/index.html
@@ -298,8 +298,8 @@ _.invoke([[5, 1, 7], [3, 2, 1]], 'sort');
       <p id="pluck">
         <b class="header">pluck</b><code>_.pluck(list, propertyName)</code>
         <br />
-        An optimized version of what is perhaps the most common use-case for 
-        <b>map</b>: returning a list of property values.
+        An convenient version of what is perhaps the most common use-case for 
+        <b>map</b>: extracting a list of property values.
       </p>
       <pre>
 var stooges = [{name : 'moe', age : 40}, {name : 'larry', age : 50}, {name : 'curly', age : 60}];
diff --git a/underscore.js b/underscore.js
index 7a3d43646..444ee010f 100644
--- a/underscore.js
+++ b/underscore.js
@@ -149,11 +149,9 @@
     });
   };
   
-  // Optimized version of a common use case of map: fetching a property.
+  // Convenience version of a common use case of map: fetching a property.
   _.pluck = function(obj, key) {
-    var results = [];
-    _.each(obj, function(value){ results.push(value[key]); });
-    return results;
+    return _.map(obj, function(value){ return value[key]; });
   };
   
   // Return the maximum item or (item-based computation).
@@ -357,18 +355,12 @@
   
   // Retrieve the names of an object's properties.
   _.keys = function(obj) {
-    return _.reduce(obj, [], function(memo, value, key) { 
-      memo.push(key);
-      return memo;
-    });
+    return _.map(obj, function(value, key){ return key; });
   };
   
   // Retrieve the values of an object's properties.
   _.values = function(obj) {
-    return _.reduce(obj, [], function(memo, value) { 
-      memo.push(value); 
-      return memo; 
-    });
+    return _.map(obj, identity);
   };
   
   // Extend a given object with all of the properties in a source object.