Example.js

class BallFactory {
    constructor(type) {
        this.createBall = function(type) {
            let ball;
            if (type == "football" || type === "soccer") ball = new Football();
            else if (type === "basketball") ball = new Basketball();
            ball.roll = function() {
                return `The ${this._type} is rolling.`;
            }

            return ball;
        }
    }
}

class Football {
    constructor() {
        this._type = 'football';
        this.kick = function() {
            return 'You kicked the football.';
        }
    }
}

class Basketball {
    constructor() {
        this._type = 'basketball';
        this.kick = function() {
            return 'You kicked the basketball.';
        }
    }
}

const factory = new BallFactory();
const myFootball = factory.createBall('football');
const myBasketball = factory.createBall('basketball');

console.log(myFootball.roll()); // The football is rolling.
console.log(myBasketball.roll()); // The basketball is rolling.
console.log(myFootball.kick()); // You kicked the football.
console.log(myBasketball.bounce()); // You bounced the basketball.