Interface to buy food from the supermarket.

supermarket.js

// interface for food
interface Food {
  name: string;
  calories: number;
}

// interface for refrigerator
interface Refrigerator {
  food: Food[];
  addFood(food: Food): void;
  getFood(foodName: string): Food | undefined;
}

// interface for supermarket
interface Supermarket {
  food: Food[];
  buyFood(foodName: string): Food | undefined;
}

// initialize refrigerator
let refrigerator: Refrigerator = {
  food: [],
  addFood(food: Food) {
    this.food.push(food);
  },
  getFood(foodName: string) {
    let food = this.food.find((food) => food.name === foodName);
    if (food) {
      this.food.splice(this.food.indexOf(food), 1);
      return food;
    }
  },
};

// initialize supermarket
let supermarket: Supermarket = {
  food: [],
  buyFood(foodName: string) {
    let food = this.food.find((food) => food.name === foodName);
    if (food) {
      this.food.splice(this.food.indexOf(food), 1);
      return food;
    }
  },
};

// if there is no 'pineapple' buy it from the supermarket.
if (!refrigerator.getFood("pineapple")) {
  const pineapple = supermarket.buyFood("pineapple");
  if (pineapple) {
    refrigerator.addFood(pineapple);
  }
}