Simple inheritance implementation in JavaScript

gistfile1.txt

window.Class = (function () {
  
  function subclass(superclass, proto) {
    proto = proto || {};
    var constructor = proto.constructor;
    if (!constructor) {
      constructor = proto.constructor = function () {};
    }
    
    if (superclass) {
      var F = function () {};
      F.prototype = superclass.prototype;
      constructor.prototype = new F();
      constructor.superclass = superclass.prototype;
    }
    
    for (var p in proto) {
      if (proto.hasOwnProperty(p)) {
        constructor.prototype[p] = proto[p];
      }
    }
    constructor.subclass = function (proto) {
      return subclass(constructor, proto);
    };
    
    return constructor;
  }

  return function Class(proto) {
    return subclass(null, proto);
  };
  
}());

gistfile2.js

var Person = Class({
  constructor: function (name) {
    this.name = name;
  },
  say: function (message) {
    return this.name + ' says: ' + message;
  }
});

var Pirate = Person.subclass({
  constructor: function (name) {
    Pirate.superclass.constructor('Capt\'n ' + name);
  },
  say: function (message) {
    return Pirate.superclass.say(message) + ' Arr!!';
  }
});

var blackbeard = new Pirate('Blackbeard');
blackbeard.say('Ahoy, me mateys!'); // Capt'n Blackbeard says: Ahoy, me mateys! Arr!!