Refactoring of Irakli Gonzala's extend() from git://gist.github.com/1361599.git

esSubclass.js

Object.defineProperty(Object, 'mergeDescriptors', {
  value: function() {
    // Shallow copy of the argument property descriptors, right most wins
    //
    var properties = {}
    Array.prototype.slice.call(arguments).forEach(function(source) {
      Object.getOwnPropertyNames(source).forEach(function(name) {
        properties[name] = Object.getOwnPropertyDescriptor(source, name)
      })
    })
    return properties;
  }
});

Object.defineProperty(Object, 'subclass', {
  value: function(prototype, statics) {
    var constructor = function () {
      // |instance| ProtoLink points to |statics.prototype| points to |this.prototype| 
      var instance = Object.create(prototype)
      // |initialize| becomes special; presumably Function.prototype.initialize is defn empty.
      prototype.initialize.apply(instance, arguments)
      return instance
    }

    // constructor prototype chains this.prototype; properties from shallow merger
    //
    Object.defineProperties(constructor, statics)

    return constructor
  }
});

Object.defineProperty(Object, 'extend', {
  value: function() {
    var properties = Object.mergeDescriptors.apply(null, arguments);
    var statics = {}

    // The property descriptors from |this|
    //
    Object.getOwnPropertyNames(this).forEach(function(name) {
      if (!(name in Function.prototype))
        statics[name] = Object.getOwnPropertyDescriptor(this, name)
    }, this)

    // ProtoLink to |this.prototype| (if any); properties from shallow merger
    var prototype = statics.prototype = Object.create(this.prototype, properties)
    return Object.subclass(prototype, statics);
  }
});