index.js

var DogClass = AnimalClass.extend(function (super_) {
  return {
    name: 'DogClass',
    method: {
      constructor: function (params) {
        super_.constructor.call(this, params);
        this._voice = 'bow wow';
      },
      cry: function() {
        return super_.cry(this._name, this._voice);
      }
    }
  }
});