Versatile prototypical inheritance in JavaScript (+ underscore.js for convenience)

inheritance.js

var App = {
  Models : {}
}

// App.Models.Model
// Contains methods to be inherited by all other models
App.Models.Model = Object.create( {}, {
  // no model ids shall be reassignable
  new : {value : function (options, properties) {
    var id = options.id; // required for get/set to work

    // extending with options allows for custom attributes on .new
    return _.extend( Object.create( this, _.extend( properties, {
      id : {
        get : function () { return id; },
        set : function (value) {
          if (value && !id) { id = value; }
        }
      },
    })), options );
  }},
  edit : {value : function (options) {
    _.each( options, function (value, key) {
      if (this.hasOwnProperty( key )) {
        this[key] = value;
      }
    }.bind( this ));
    return this;
  }}
});

App.Models.Animal = Object.create( App.Models.Model, {
  // override new to set "class" properties
  new : {value : function (options) {
    options = options || {};
    options.name = options.name || "Unnamed Animal"; // set default

    var alive = options.alive || true; // required for get/set to work

    // super
    return App.Models.Model.new.call( this, options, {
      // methods which use the options object must be defined within this
      // closure so they have access to it
      originalName : {
        value : options.name,
        writable : false // false is default but this makes that explicit
      },
      // this alive method has to be defined within this closure
      // because of the need for a alive variable
      alive : { 
        get : function () { return alive; },
        set : function (value) {
          // once the animal is dead, we don't want to allow its revival
          if (alive == true) { alive = value; }
        }
      }
    });
  }},
  eat : {value : function () {
    return this.name + " ate.";
  }}
});

App.Models.Dog = Object.create( App.Models.Animal, {
  // override new to set "subclass" properties
  new : {value : function (options) {
    options = options || {};
    options.name = options.name || "Spot"; // set default
    // super
    return App.Models.Animal.new.call( this, options );
  }},
});

App.Models.Cat = Object.create( App.Models.Animal, {
  // override methods
  eat : {value : function () {
    return this.name + " is on a diet.";
  }}
});

var dog = App.Models.Dog.new();
console.log( dog.name ); // Spot
console.log( dog.eat() ); // Spot ate.
console.log( dog.originalName ); // Spot
dog.originalName = "derp";
console.log( dog.originalName ); // Spot
dog.name = "Spot 2.0"
console.log( dog.name ); // Spot 2.0
console.log( dog.originalName ); // Spot

var will = App.Models.Dog.new( {name : "Will"} );
console.log( will.name ); // Will
console.log( will.eat() ); // Will ate.
console.log( will.alive ); // true
will.alive = false;
console.log( will.alive ); // false
will.alive = true;
console.log( will.alive ); // false

var cat = App.Models.Cat.new();
console.log( cat.eat() ); // Unnamed Animal is on a diet.

var napoleon = App.Models.Cat.new( {name : "Napoleon"} );
console.log( napoleon.id ); // undefined
napoleon.id = 1;
console.log( napoleon.id ); // 1
napoleon.id = 2;
console.log( napoleon.id ); // 1

var fuzzy = App.Models.Cat.new( {herp: "derp"} );
console.log( fuzzy.herp ); // derp