optimized keys, values, and pluck

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}];

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.