Class 方法不会给出正确的输出

Question

class CoffeeShop {  
  constructor(name, menu) {
      this.name = name;
      this.menu = menu;
      this.orders = [];
  }

  addOrder(itemName) {
    this.menu.reduce((acc, meal, i, arr) => {
      meal[itemName] ? (this.orders.push(itemName), console.log("Order Added!"), arr.splice(1)) : (console.log("This item is currently unavailable!"), arr.splice(1))
    }, [])
  }

  fulfillOrder() {
    this.orders.isEmpty ? (console.log("All orders have been fulfilled!")) : (console.log(`The ${this.orders[0]} is ready!`), this.orders.shift())
  }
}


let Shop = new CoffeeShop("Shop", [
  { item: "cinnamon roll", type: "food", price: 4.99},
  { item: "hot chocolate", type: "drink", price: 2.99},
  { item: "lemon tea", type: "drink", price: 2.50}
]);

Shop.addOrder("hot chocolate");

console.log(Shop.orders);

Shop.fulfillOrder();

console.log(Shop.orders);

输出为：

This item is currently unavailable! [] The undefined is ready! []

为什么订单列表没有变化？为什么 fullfillOrder 函数 return 与它应该 return 相反，即使条件为真？

Answer 1

我宁愿使用过滤器 - 过滤掉添加的项目

class CoffeeShop {  
  constructor(name, menu) {
      this.name = name;
      this.menu = menu;
      this.orders = [];
  }

  addOrder(itemName) {
    this.menu = this.menu.filter(i => {
    if(i.item === itemName) {
        this.orders.push(itemName),
        console.log("Order Added!")
        return false;
    }
    console.log("This item is currently unavailable!")
    return true;
    })
  }

  fulfillOrder() {
    this.orders.isEmpty ? (console.log("All orders have been fulfilled!")) : (console.log(`The ${this.orders[0]} is ready!`), this.orders.shift())
  }
}


let Shop = new CoffeeShop("Shop", [
  { item: "cinnamon roll", type: "food", price: 4.99},
  { item: "hot chocolate", type: "drink", price: 2.99},
  { item: "lemon tea", type: "drink", price: 2.50}
]);

Shop.addOrder("hot chocolate");

console.log(Shop.orders);

Shop.fulfillOrder();

console.log(Shop.orders);

Class 方法不会给出正确的输出

Class method won't give the right output

javascript

methods

class