#策略模式(Strategy)

class Market1 {
  constructor() {
    this.products = {
      cola: {
        price: 3,
        length: 20,
      },
    };
  }

  caculate(obj) {
    return this.products[obj.name].price * obj.length;
  }
}

class Market2 {
  constructor() {
    this.products = {
      cola: {
        price: 2.5,
        length: 20,
      },
    };
  }

  caculate(obj) {
    return this.products[obj.name].price * obj.length;
  }
}

class Shop {
  constructor(market) {
    this.market = market;
  }

  caculate(obj) {
    return this.market.caculate(obj);
  }
}

export { Shop, Market1, Market2 };

let market1 = new Shop(new Market1());
let market2 = new Shop(new Market2());
market1.caculate({ name: "cola", length: 3 });
market2.caculate({ name: "cola", length: 3 });