How do you write a class in Javascript? [duplicate]

Well, JavaScript is a Prototype-Based language, it does not have classes, but you can have classical inheritance, and other behavior reuse patterns through object cloning and prototyping.

Recommended articles:

• Introduction to Object-Oriented JavaScript
• JavaScript Classical Inheritance
• JavaScript Private Members
• Class-Based vs. Prototype-Based Languages

function Foo() { // constructor } Foo.prototype.bar = function() { // bar function within foo } 

Javascript uses prototype-based OO by default.

However, if you're using prototype library, for example, you can use Class.create().

http://prototypejs.org/api/class/create

It would let you to create (or inherit) a class, after that you would instantiate its instances with new.

Other libraries probably have similar facilities.

If you use a library like prototype or jQuery its a lot easier but the legacy way is to do this.

function MyClass(){ } MyClass.prototype.aFunction(){ } var instance = new MyClass(); instance.aFunction(); 

You can read more on it here http://www.komodomedia.com/blog/2008/09/javascript-classes-for-n00bs/

It's "sort of" possible. Prototype has some built-in help with writing classes in JS. Take a look at this thorough description of how you can do it.

var namedClass = Class.create({ initialize: function(name) { this.name = name; } getName: function() { return this.name; } }); var instance = new namedClass('Foobar'); 

JavaScript is based on objects, not classes. It uses prototypal inheritance, not classical inheritance.

JavaScript is malleable and easily extensible. As a result, there are many libraries that add classical inhertance to JavaScript. However, by using them you risk writing code that's difficult for most JavaScript programmers to follow.