Good Example of JavaScript's Prototype-Based Inheritance

Question

I have been programming with OOP languages for over 10 years but I'm learning JavaScript now and it's the first time I've encountered prototype-based inheritance. I tend to learn fastest by studying good code. What's a well-written example of a JavaScript application (or library) that properly uses prototypal inheritance? And can you describe (briefly) how/where prototypal inheritance is used, so I know where to start reading?

Answer 1

I would take a look at YUI, and at Dean Edward's Base library: http://dean.edwards.name/weblog/2006/03/base/

For YUI you can take a quick look at the lang module, esp. the YAHOO.lang.extend method. And then, you can browse the source of some widgets or utilities and see how they use that method.

Answer 2

There's also Microsoft's ASP.Net Ajax library http://www.asp.net/ajax/

There are a lot of good MSDN articles around that as well including this one

http://msdn.microsoft.com/en-us/magazine/cc163419.aspx

Answer 3

Douglas Crockford has a nice page on Javascript Prototypal Inheritance:

Five years ago I wrote Classical Inheritance in JavaScript. It showed that JavaScript is a class-free, prototypal language, and that it has sufficient expressive power to simulate a classical system. My programming style has evolved since then, as any good programmer's should. I have learned to fully embrace prototypalism, and have liberated myself from the confines of the classical model.

Dean Edward's Base.js, Mootools's Class or John Resig's Simple Inheritance works are ways to do classical inheritance in Javascript.

Answer 4

I suggest looking at PrototypeJS' Class.create:
Line 83 @ http://prototypejs.org/assets/2009/8/31/prototype.js

Answer 5

The best examples I've seen are in Douglas Crockford's Javascript The Good Bits (I'll update this answer with examples when I have the book to hand). It's definitely worth buying to help you get a balanced view on the language.

Douglas Crockford's is responsible for the JSON format and works at Yahoo as a Javascript guru.