Getting a class property from an instance of a Backbone.js model (without naming the class explicitly)

foo.js

var C = Backbone.Model.extend({
  foo : function() { return this.constructor.bar; }
}, {
  bar : 123
});

var ci = new C;
ci.foo();
// -> 123

var D = C.extend({}, { bar : 789 });

(new D).foo();
// -> 789

// Thanks @quackingduck! http://twitter.com/quackingduck/status/62003113367830528

// but...

var E = C.extend();
(new E).foo();
// -> undefined