This article followsRuby's open classes and inheritance in JavaScript and shows that the simpleextend function gives us the ability to simulate Ruby's Module#remove_method. Below are Ruby and JavaScript versions to show this at work.

Ruby

class Person  def initialize(first, last)    @first = first    @last = last  end  def reverse    @last + ', ' + @first  endendclass Employee < Person  def initialize(first, last, id)    super(first, last)    @id = id  end  def reverse    super + ': ' + @id.to_s  endendpeter = Employee.new('Peter', 'Michaux', 3)puts peter.reverse # Michaux, Peter: 3class Employee  remove_method :reverseendputs peter.reverse # Michaux, Peter

JavaScript

var Class = {  extend: function(subclass, superclass) {            function D() {}            D.prototype = superclass.prototype;            subclass.prototype = new D();            subclass.prototype.constructor = subclass;            subclass.superclass = superclass;            subclass.superproto = superclass.prototype;          }};function Person(first, last) {  this.first = first;  this.last = last;}Person.prototype.reverse = function() {  return this.last + ', ' + this.first;};function Employee(first, last, id) {  Employee.superclass.call(this, first, last);  this.id = id;}Class.extend(Employee, Person);Employee.prototype.reverse = function() {  return Employee.superproto.reverse.call(this) + ': ' + this.id;};var peter = new Employee('Peter', 'Michaux', 3);document.write(peter.reverse()); // Michaux, Peter: 3delete Employee.prototype.reverse;document.write(peter.reverse()); // Michaux, Peter