Add keys, values, pairs, invert, pick, omit, each, and other

underscore methods to models

backbone.js

@@ -544,6 +544,20 @@
 
   });
 
+  // Underscore methods that we want to implement on the Model.
+  var methods =  ['each', 'forEach', 'map', 'collect', 'contains', 'include',
+    'sortBy', 'groupBy', 'size', 'keys', 'values', 'pairs', 'invert', 'pick',
+    'omit', 'isEqual', 'isEmpty', 'chain'];
+
+  // Mix in each Underscore method as a proxy to `Model#attributes`.
+  _.each(methods, function(method) {
+    Model.prototype[method] = function() {
+      var args = slice.call(arguments);
+      args.unshift(this.attributes);
+      return _[method].apply(_, args);
+    };
+  });
+
   // Backbone.Collection
   // -------------------
 

test/model.js

@@ -111,6 +111,37 @@ $(document).ready(function() {
     equal(model.url(), '/nested/1/collection/2');
   });
 
+  test("underscore methods", 19, function() {
+    var model = new Backbone.Model({ 'foo': 'a', 'bar': 'b', 'baz': 'c' });
+    var model2 = model.clone();
+    deepEqual(model.keys(), ['foo', 'bar', 'baz']);
+    deepEqual(model.values(), ['a', 'b', 'c']);
+    deepEqual(model.pairs(), [['foo', 'a'], ['bar', 'b'], ['baz', 'c']]);
+    deepEqual(model.invert(), { 'a': 'foo', 'b': 'bar', 'c': 'baz' });
+    deepEqual(model.pick('foo', 'baz'), {'foo': 'a', 'baz': 'c'});
+    deepEqual(model.omit('foo', 'bar'), {'baz': 'c'});
+    model.each(function(attr, index, attrs) {
+      ok(true);
+    });
+    equal(model.isEqual(model2.attributes), true);
+    equal(model.isEqual({ 'foo': 'a', 'bop': 'd' }), false);
+    equal(model.isEmpty(), false);
+    equal(model.size(), 3);
+    equal(model.contains('foo'), false);
+    equal(model.contains('b'), true);
+    equal(model.chain().keys().contains('foo').value(), true);
+    deepEqual(model.sortBy(function(val) { return val === 'b' }), ["c", "a", "b"]);
+    deepEqual(model.groupBy(), {
+      'a': ['a'],
+      'b': ['b'],
+      'c': ['c']
+    });
+    var prefixed = model.map(function(val, key, attrs){
+      return 'book-' + key;
+    });
+    deepEqual(prefixed, ['book-foo', 'book-bar', 'book-baz']);
+  });
+
   test("clone", 10, function() {
     var a = new Backbone.Model({ 'foo': 1, 'bar': 2, 'baz': 3});
     var b = a.clone();