cd.js

class CD {

    constructor(price, stock, title, artist) {
        this.price = price;
        this.stock = stock;
        this.title = title;
        this.artist = artist;
    }

    buy(payments, creditCard) {
        if(this.stock == 0){
            throw new OutOfStockError();
        }
        let paymentAccepted = payments.process(this.price, creditCard);
        if(paymentAccepted){
            this.stock--;
        }
    }

    matches(title, artist) {
        return this.title == title && this.artist == artist;
    }
}