ES6 пример наследования

index.js

// ES6
class ProductES {
    constructor(brand, price, discount) {
        this.brand = brand;
        this.price = price;
        this.discount = discount;
    }

    get brand() {
        return this._brand;
    }

    set brand(newName) {
        this._brand = newName;
    }

    sum() {
        return (this.price * (100 - this.discount)) / 100;
    }

    static plus(x, y) {
        return x + y;
    }
}

class CustomES extends ProductES {
    constructor(brand, price, discount, day) {
        super(brand, price, discount);
        this.day = day;
    }

    getBrandAndDiscount () {
        return super.sum() + this.price;
    }
}

const newProduct = new ProductES('Samsung', 200, 10);
const newCustom = new CustomES('Apple', 20000, 10, 'Wednesday');
console.log(newProduct);
console.log(newProduct.sum());
console.log(ProductES.plus(24500, 79500));

console.log(newCustom.day)
console.log(newCustom.price)
console.log(newCustom.getBrandAndDiscount())