如何将变量用作对象内的索引？ (Javascript)

Question

我正在尝试使用变量 appetizer、main 和甜点作为数组的索引，但我不知道如何执行此操作。这是第 49 行。

    var menu = {
  _courses: {
    appetizers: [],
    mains: [],
    desserts: []
  },
get appetizers() {
   return this._courses.appetizers;
},
get mains() {
  return this._courses.mains;
},
get desserts() {
  return this._courses.desserts;
},
set appetizers(appetizers) {
    this.courses.desserts = desserts;
  },
set mains(mains) {
   this.mains = mains;
},
set desserts(desserts) {
     this.desserts = desserts;
  },
  get courses() {
    return {
      appetizers,
      mains,
      desserts,
    };
  },
  addDishToCourse (courseName, dishName, dishPrice) { 
   const dish = {
     food: courseName,
     name: dishName,
     price: dishPrice,

   };
  return this._courses[courseName].push(dish);
  },
     getRandomDishFromCourse: function(courseName) {
    var dishes = this._courses[courseName];
     if (dishes !== undefined) {
       var randomIndex = Math.floor(Math.random() * dishes.length);
      return randomIndex;
     }
  },

  generateRandomMeal: function() { //This is the problem.
   var appetizer = this.getRandomDishFromCourse('appetizers');
    var main = this.getRandomDishFromCourse('mains');
    var dessert = this.getRandomDishFromCourse('dessert');
    return 'Your meal is ' + appetizer + ', ' + main + ', and ' + dessert + '. The total price is $' +/* this.dish.price */ 8 + '.'; 
  }
}; 

menu.addDishToCourse('appetizers', 'Bread Loaf', 4.25);
menu.addDishToCourse('appetizers', 'Caesar Salad', 3.50);
menu.addDishToCourse('appetizers', 'Small Soup', 4.50);
menu.addDishToCourse('mains', 'Steak Dinner', 20.00);
menu.addDishToCourse('mains', 'spaghetti', 16.00);
menu.addDishToCourse('mains', 'Turkey Dinner', 18.99);
menu.addDishToCourse('desserts', 'Icecream', 5.99);
menu.addDishToCourse('desserts', 'Cookies', 5.99);
menu.addDishToCourse('desserts', 'Jello', 5.99);


var meal = menu.generateRandomMeal();
console.log(meal);

我已尝试使用此代码：

this.appetizers[appetizer]
this.mains[main]
this.desserts[dessert]

但这只是返回 Object 对象而不是索引号。

Answer 1

您的getRandomDishFromCourse 从传递的courseName 中选择一个随机索引，但它只返回索引 - 它应该通过return dishes[randomIndex]; 返回一个菜对象。

菜品退回后，在generateRandomMeal中，您需要选择每个菜品的name属性进行打印，并将所有prices相加得出总价：

  getRandomDishFromCourse: function(courseName) {
    var dishes = this._courses[courseName];
    if (dishes !== undefined) {
      var randomIndex = Math.floor(Math.random() * dishes.length);
      return dishes[randomIndex];
    }
  },

  generateRandomMeal: function() { //This is the problem.
    var appetizer = this.getRandomDishFromCourse('appetizers');
    var main = this.getRandomDishFromCourse('mains');
    var dessert = this.getRandomDishFromCourse('desserts');
    return 'Your meal is ' + appetizer.name + ', ' + main.name + ', and ' + dessert.name +
      '. The total price is $' + (appetizer.price + main.price + dessert.price).toFixed(2)
  }

var menu = {
  _courses: {
    appetizers: [],
    mains: [],
    desserts: []
  },
  get appetizers() {
    return this._courses.appetizers;
  },
  get mains() {
    return this._courses.mains;
  },
  get desserts() {
    return this._courses.desserts;
  },
  set appetizers(appetizers) {
    this.courses.desserts = desserts;
  },
  set mains(mains) {
    this.mains = mains;
  },
  set desserts(desserts) {
    this.desserts = desserts;
  },
  get courses() {
    return {
      appetizers,
      mains,
      desserts,
    };
  },
  addDishToCourse(courseName, dishName, dishPrice) {
    const dish = {
      food: courseName,
      name: dishName,
      price: dishPrice,

    };
    return this._courses[courseName].push(dish);
  },
  getRandomDishFromCourse: function(courseName) {
    var dishes = this._courses[courseName];
    if (dishes !== undefined) {
      var randomIndex = Math.floor(Math.random() * dishes.length);
      return dishes[randomIndex];
    }
  },

  generateRandomMeal: function() { //This is the problem.
    var appetizer = this.getRandomDishFromCourse('appetizers');
    var main = this.getRandomDishFromCourse('mains');
    var dessert = this.getRandomDishFromCourse('desserts');
    return 'Your meal is ' + appetizer.name + ', ' + main.name + ', and ' + dessert.name +
      '. The total price is $' + (appetizer.price + main.price + dessert.price).toFixed(2)
  }
};

menu.addDishToCourse('appetizers', 'Bread Loaf', 4.25);
menu.addDishToCourse('appetizers', 'Caesar Salad', 3.50);
menu.addDishToCourse('appetizers', 'Small Soup', 4.50);
menu.addDishToCourse('mains', 'Steak Dinner', 20.00);
menu.addDishToCourse('mains', 'spaghetti', 16.00);
menu.addDishToCourse('mains', 'Turkey Dinner', 18.99);
menu.addDishToCourse('desserts', 'Icecream', 5.99);
menu.addDishToCourse('desserts', 'Cookies', 5.99);
menu.addDishToCourse('desserts', 'Jello', 5.99);


var meal = menu.generateRandomMeal();
console.log(meal);

（总数后需要toFixed(2)以避免浮点问题）

Answer 2

您需要使用索引来访问数组中的项目。您现在拥有它的方式只会打印随机索引。

var menu = {
  _courses: {
    appetizers: [],
    mains: [],
    desserts: []
  },
  get appetizers() {
    return this._courses.appetizers;
  },
  get mains() {
    return this._courses.mains;
  },
  get desserts() {
    return this._courses.desserts;
  },
  set appetizers(appetizers) {
    this.courses.desserts = desserts;
  },
  set mains(mains) {
    this.mains = mains;
  },
  set desserts(desserts) {
    this.desserts = desserts;
  },
  get courses() {
    return {
      appetizers: this.appetizers,
      mains: this.mains,
      desserts: this.desserts,
    };
  },
  addDishToCourse(courseName, dishName, dishPrice) {
    const dish = {
      food: courseName,
      name: dishName,
      price: dishPrice,

    };
    return this._courses[courseName].push(dish);
  },
  getRandomDishFromCourse: function(courseName) {
    var dishes = this._courses[courseName];
    if (dishes !== undefined) {
      var randomIndex = Math.floor(Math.random() * dishes.length);
      return randomIndex;
    }
  },

  generateRandomMeal: function() { //This is the problem.
    var appetizer = this.appetizers[this.getRandomDishFromCourse('appetizers')];
    var main = this.mains[this.getRandomDishFromCourse('mains')];
    var dessert = this.desserts[this.getRandomDishFromCourse('desserts')];
    return 'Your meal is ' + appetizer.name + ', ' + main.name + ', and ' + dessert.name + '. The total price is $' + /* this.dish.price */ 8 + '.';
  }
};

menu.addDishToCourse('appetizers', 'Bread Loaf', 4.25);
menu.addDishToCourse('appetizers', 'Caesar Salad', 3.50);
menu.addDishToCourse('appetizers', 'Small Soup', 4.50);
menu.addDishToCourse('mains', 'Steak Dinner', 20.00);
menu.addDishToCourse('mains', 'spaghetti', 16.00);
menu.addDishToCourse('mains', 'Turkey Dinner', 18.99);
menu.addDishToCourse('desserts', 'Icecream', 5.99);
menu.addDishToCourse('desserts', 'Cookies', 5.99);
menu.addDishToCourse('desserts', 'Jello', 5.99);

//console.log(JSON.stringify(menu, null, 4));

console.log(menu.generateRandomMeal());