A simple, if old, class system for Javascript.

myclass.js

// The best javascript class system ever! This is old news to most, but
// more and more I find myself coming back to this. I don't have a vendetta
// against the `new` keyword. I just sometimes want encapsulation in a way
// that doesn't feel like a complete hack.

// Start with a closure
var vehicle = function() {

    // Use Object.create
    var vehicle = Object.create({});

    // Public properties
    vehicle.terrain = null;

    // True encapsulation!
    var wheels = 0;

    // Add some methods
    vehicle.wheels = function() {
        return wheels;
    }

    vehicle.setWheels = function(count) {
        wheels = count;
        return this;
    }

    // For the sake of demonstrating 'super-like' behavior
    vehicle.whoAmI = function() {
        return "vehicle";
    }

    return vehicle;
}

// Create a subclass
var car = function() {
    var car = Object.create(vehicle());

    car.terrain = 'ground';

    // Wheels on the car go round and round
    car.setWheels(4);

    // Who you be?
    car.whoAmI = function() {
        return "car";
    }

    return car;
}

// Usage
var mycar = car();

// Returns '4'
mycar.wheels();

// Returns 'car'
mycar.whoAmI();

// Returns 'vehicle', Super-like behavior!
Object.getPrototypeOf(mycar).whoAmI();

// Returns 'ground'
mycar.terrain;

// Returns 'null'
Object.getPrototypeOf(mycar).terrain;

// If you're worried about this being portable...
// From https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/create
if (!Object.create) {
    Object.create = function (o) {
        if (arguments.length > 1) {
            throw new Error('Object.create implementation only accepts the first parameter.');
        }
        function F() {}
        F.prototype = o;
        return new F();
    };
}