patterns

class Singleton {
    constructor() {
        if (Singleton.instance) {
            return Singleton.instance;
        }
        this.data = [];
        Singleton.instance = this;
    }

    getData() {
        return this.data;
    }

    setData(data) {
        this.data = data;
    }
}

const singleton1 = new Singleton();
const singleton2 = new Singleton();

singleton1.setData([1, 2, 3]);
console.log(singleton2.getData()); // Output: [1, 2, 3]


class Subject {
    constructor() {
        this.observers = [];
    }

    subscribe(observer) {
        this.observers.push(observer);
    }

    unsubscribe(observer) {
        this.observers = this.observers.filter(obs => obs !== observer);
    }

    notify(data) {
        this.observers.forEach(observer => observer.update(data));
    }
}

class Observer {
    update(data) {
        console.log(`Observer received data: ${data}`);
    }
}

const subject = new Subject();
const observer1 = new Observer();
const observer2 = new Observer();

subject.subscribe(observer1);
subject.subscribe(observer2);

subject.notify("Hello, Observers!"); // Both observers will log the message


class Car {
    constructor() {
        this.type = 'Car';
    }
}

class Truck {
    constructor() {
        this.type = 'Truck';
    }
}

class VehicleFactory {
    createVehicle(vehicleType) {
        switch (vehicleType) {
            case 'car':
                return new Car();
            case 'truck':
                return new Truck();
            default:
                throw new Error('Unknown vehicle type');
        }
    }
}

const factory = new VehicleFactory();
const myCar = factory.createVehicle('car');
const myTruck = factory.createVehicle('truck');

console.log(myCar.type); // Output: Car
console.log(myTruck.type); // Output: Truck


const Module = (function () {
    let privateVar = 'I am private';

    function privateMethod() {
        console.log(privateVar);
    }

    return {
        publicMethod: function () {
            privateMethod();
        }
    };
})();

Module.publicMethod(); // Output: I am private


class Car {
    constructor() {
        this.cost = 20000;
    }

    getCost() {
        return this.cost;
    }
}

class Sunroof {
    constructor(car) {
        this.car = car;
    }

    getCost() {
        return this.car.getCost() + 1500;
    }
}

class LeatherSeats {
    constructor(car) {
        this.car = car;
    }

    getCost() {
        return this.car.getCost() + 2000;
    }
}

let myCar = new Car();
myCar = new Sunroof(myCar);
myCar = new LeatherSeats(myCar);

console.log(myCar.getCost()); // Output: 23500