var chicken = new Chicken();

YAHOO.lang is packaged with the YAHOO Global Object

YAHOO.lang comes bundled with the YAHOO Global Object. To add the YAHOO Global Object, include the following in your markup:

If you are using any other YUI component on your page, you should already have YAHOO.lang available.

Creating a class hierarchy

In this example, we create a class YAHOO.example.Bird then create a subclass YAHOO.example.Chicken. Bird = function (name) { this.name = name; }; Bird.prototype.flighted = true; // Default for all Birds Bird.prototype.isFlighted = function () { return this.flighted }; Bird.prototype.getName = function () { return this.name }; Chicken = function (name) { // Chain the constructors Chicken.superclass.constructor.call(this, name); }; // Chickens are birds YAHOO.lang.extend(Chicken, Bird); // Define the Chicken prototype methods/members Chicken.prototype.flighted = false; // Override default for all Chickens

instanceof many classes

Unlike classes composed with augmentation, extending subclasses are also considered instances of their superclass and all classes higher up the inheritance tree.

We'll create an instance of YAHOO.example.Chicken and run some instanceof and method tests against it.

Other architecture strategies

Take a look at YAHOO.lang.augmentProto and YAHOO.lang.augmentObject for different strategies of managing your code structure.