February 13, 2001 - Inheriting and Overriding Methods | WebReference

February 13, 2001 - Inheriting and Overriding Methods

Yehuda Shiran February 13, 2001
Inheriting and Overriding Methods
Tips: February 2001

Yehuda Shiran, Ph.D.
Doc JavaScript

Inheritance is a very important requirement for an object-oriented language. JavaScript does not support any OO primitives in its language, but you can implement most of the stuff you need. Let's look at the following example:

function superClass() {
  this.bye = superBye;
  this.hello = superHello;
  function superHello() {
    return "Hello from superClass";
  function superBye() {
    return "Bye from superClass";
function subClass() {
  this.inheritFrom = superClass;
  this.bye = subBye;
  function subBye() {
	return "Bye from subClass";
var newClass = new subClass();

We have a super class , superClass, and a sub class, subClass. superClass defines two methods: bye() and hello(). subClass inherits these two methods by:

this.inheritFrom = superClass;
and overrides the bye() method. When clicking here, you trigger the evaluation of bye() and hello() from the sub class. You can judge from the alert boxes that indeed the hello() method is as defined by the super class, while the bye method is as overridden by the sub class.