Merge pull request #2074 from jridgewell/create

Add _.create method

Author: jashkenas

test/objects.js

@@ -282,6 +282,32 @@
     equal(_.clone(null), null, 'non objects should not be changed by clone');
   });
 
+  test('create', function() {
+    var Parent = function() {};
+    Parent.prototype = {foo: function() {}, bar: 2};
+
+    _.each(['foo', null, undefined, 1], function(val) {
+      deepEqual(_.create(val), {}, 'should return empty object when a non-object is provided');
+    });
+
+    ok(_.create([]) instanceof Array, 'should return new instance of array when array is provided');
+
+    var Child = function() {};
+    Child.prototype = _.create(Parent.prototype);
+    ok(new Child instanceof Parent, 'object should inherit prototype');
+
+    var func = function() {};
+    Child.prototype = _.create(Parent.prototype, {func: func});
+    strictEqual(Child.prototype.func, func, 'properties should be added to object');
+
+    Child.prototype = _.create(Parent.prototype, {constructor: Child});
+    strictEqual(Child.prototype.constructor, Child);
+
+    Child.prototype.foo = 'foo';
+    var created = _.create(Child.prototype, new Child);
+    ok(!created.hasOwnProperty('foo'), 'should only add own properties');
+  });
+
   test('isEqual', function() {
     function First() {
       this.value = 1;

underscore.js

@@ -1048,6 +1048,15 @@
   // Fill in a given object with default properties.
   _.defaults = createAssigner(_.allKeys, true);
 
+  // Creates an object that inherits from the given prototype object.
+  // If additional properties are provided then they will be added to the
+  // created object.
+  _.create = function(prototype, props) {
+    var result = baseCreate(prototype);
+    if (props) _.assign(result, props);
+    return result;
+  };
+
   // Create a (shallow-cloned) duplicate of an object.
   _.clone = function(obj) {
     if (!_.isObject(obj)) return obj;