Inherit and extend defaults when extending a Backbone model

backbone-defaults-inheritance.js

var Parent = Backbone.Model.extend({
    
  defaults: function () {
    return {
      prop: 'value',
      anotherProp: 'anotherValue'
    }
  }
});

var Child = Parent.extend({
  defaults: function () {
    
    var parentDefaults = Parent.prototype.defaults;
    
    if (_.isFunction(parentDefaults)) {
      parentDefaults = parentDefaults.call();
    }
    
    return _.chain(parentDefaults)
            .clone()
            .extend({
              prop: 'newValue',
              newProp: 'newValueToo'
            })
            .value();
  }
});

console.log(new Parent().attributes);
console.log(new Child().attributes);