protected-members.ts

abstract class Sizes {
  constructor(protected sizes: string[]) {}

  set availableSizes(sizes: string[]) {
    this.sizes = sizes;
  }

  get availableSizes() {
    return this.sizes;
  }
}

class Pizza extends Sizes {
  public toppings: string[] = [];

  constructor(readonly name: string, sizes: string[]) {
    super(sizes);
  }

  public updateSizes(sizes: string[]) {
    this.sizes = sizes;
  }

  public addTopping(topping: string) {
    this.toppings.push(topping);
  }
}

const pizza = new Pizza("Peuperuni", ["small", "medium"]);
console.log(pizza.availableSizes);

pizza.updateSizes(["large, extra-large"]);
console.log(pizza.availableSizes);