added $.by()

specs/lib/array_spec.js

@@ -21,8 +21,16 @@
  */
 (function () {
     describe('Array functions', {
-        "should ...": function () {
-            value_of(true).should_be_true();
+        "should return a sort callback to order by object property": function () {
+            var zhanna = {name: 'Zhanna', age: 27},
+                ira = {name: 'Irina', age: 27},
+                brioche = {name: 'Brioche', age: 1},
+                mathieu = {name: 'Mathieu', age: 38},
+                func = $.by('age');
+
+            value_of(func(zhanna, mathieu)).should_be(-1);
+            value_of(func(zhanna, ira)).should_be(0);
+            value_of(func(zhanna, brioche)).should_be(1);
         }
     });
 })();

src/array.js

@@ -3,11 +3,30 @@
  */
 $.extend({
     /*
-     * compact: ...
+     * by:  Function by takes a member name string and an 
+     *      optional minor comparison function and returns 
+     *      a comparison function that can be used to sort an 
+     *      array of objects that contain that member. The 
+     *      minor comparison function is used to break ties
+     *      when the o[name] and p[name] are equal.
+     *      (Douglas Crockford - Javascript: The Good Parts)
      */
-    compact: function (array) {
-        return array;
+    by:  function (name, minor) { 
+        return function (o, p) { 
+            var a, b; 
+            if (o && p && typeof o === 'object' && typeof p === 'object') { 
+                a = o[name]; 
+                b = p[name]; 
+                if (a === b) { 
+                    return typeof minor === 'function' ? minor(o, p) : 0; 
+                } 
+                if (typeof a === typeof b) { 
+                    return a < b ? -1 : 1; 
+                } 
+                return typeof a < typeof b ? -1 : 1; 
+            }
+            throw { name: 'Error', message: 'Expected an object when sorting by ' + name }; 
+        };
     }
 });
 
-