JavaScript -TypeError when I use underscore in naming object array and in get and set method

Question

I have completed a JS project that creates a menu, populates it with appetizers, mains and desserts including their price and stores in arrays in menu object. A random selection of appetizers, mains and desserts can be called along with the total price of the meal.

This code works fine but it is not what i want:

const 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.appetizers = appetizers;
  },
  set mains(mains) {
    this._courses.mains = mains;
  },
  set desserts(desserts) {
    this._courses.desserts = desserts;
  },
  get courses() {
    return {
      appetizers: this._courses.appetizers,
      mains: this._courses.mains,
      desserts: this._courses.desserts
    };
    },

    addDishToCourse(courseName, dishName, dishPrice) {
      let dish = {
        name: dishName,
        price: dishPrice
      };

      this._courses[courseName].push(dish);
    },

    getRandomDishFromCourse(courseName) {
      let dishes = this._courses[courseName];
      let randomIndex = Math.floor(Math.random() * dishes.length);
      return dishes[randomIndex];
    },

generateRandomMeal() {    
    let appetizer = this.getRandomDishFromCourse('appetizers');
    let main = this.getRandomDishFromCourse('mains');
    let dessert = this.getRandomDishFromCourse('desserts');
    let totalCost = appetizer.price + main.price + dessert.price;
    
    return `Your meal is ${appetizer.name}, ${main.name} and ${dessert.name} and it costs £${totalCost.toFixed(2)}.`;
    },

};

menu.addDishToCourse('appetizers', 'prawncocktail', 4.75);
menu.addDishToCourse('appetizers', 'soup', 3.77);
menu.addDishToCourse('appetizers', 'bread and butter', 1.25);

menu.addDishToCourse('mains', 'steak', 11.75);
menu.addDishToCourse('mains', 'vegetarian', 9.75);

menu.addDishToCourse('desserts', 'ice cream', 3.99);
menu.addDishToCourse('desserts', 'cheese and biscuits', 2.99);

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

I want _appetizers: [] not appetizers: []

I have tried to find online documentation to help but so far have failed!

Adding the underscore "_" to appetizers _appetizers in _courses and in the get and set methods causes an error.

This code throws a TypeError

const 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._appetizers = appetizers;
  },
  set mains(mains) {
    this._courses.mains = mains;
  },
  set desserts(desserts) {
    this._courses.desserts = desserts;
  },
  get courses() {
    return {
      appetizers: this._courses._appetizers,
      mains: this._courses.mains,
      desserts: this._courses.desserts
    };
    },

    addDishToCourse(courseName, dishName, dishPrice) {
      let dish = {
        name: dishName,
        price: dishPrice
      };

      this._courses[courseName].push(dish);
    },

    getRandomDishFromCourse(courseName) {
      let dishes = this._courses[courseName];
      let randomIndex = Math.floor(Math.random() * dishes.length);
      return dishes[randomIndex];
    },

generateRandomMeal() {    
    let appetizer = this.getRandomDishFromCourse('appetizers');
    let main = this.getRandomDishFromCourse('mains');
    let dessert = this.getRandomDishFromCourse('desserts');
    let totalCost = appetizer.price + main.price + dessert.price;
    
    return `Your meal is ${appetizer.name}, ${main.name} and ${dessert.name} and it costs £${totalCost.toFixed(2)}.`;
    },

};

menu.addDishToCourse('appetizers', 'prawncocktail', 4.75);
menu.addDishToCourse('appetizers', 'soup', 3.77);
menu.addDishToCourse('appetizers', 'bread and butter', 1.25);

menu.addDishToCourse('mains', 'steak', 11.75);
menu.addDishToCourse('mains', 'vegetarian', 9.75);

menu.addDishToCourse('desserts', 'ice cream', 3.99);
menu.addDishToCourse('desserts', 'cheese and biscuits', 2.99);

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

Error:

/home/ccuser/workspace/learn-javascript-objects-meal-maker/app.js:39
      this._courses[courseName].push(dish);
                               ^

TypeError: Cannot read property 'push' of undefined
    at Object.addDishToCourse (/home/ccuser/workspace/learn-javascript-objects-meal-maker/app.js:39:32)```

gbalduzzi · Accepted Answer · 2021-06-25 12:32:47Z

1

You should add the underscore when you call addDishToCourse as well:

menu.addDishToCourse('_appetizers', 'prawncocktail', 4.75);
menu.addDishToCourse('_appetizers', 'soup', 3.77);
menu.addDishToCourse('_appetizers', 'bread and butter', 1.25);

Otherwise, courseName is 'appetizers' (no underscore) and accessing this._courses[courseName] = this._courses['appetizers'] results in undefined:

this._courses['appetizers'].push(dish);
             ^^^^^^^^^^^^^^

answered Jun 25, 2021 at 12:32

gbalduzzi

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1 Comment

the_end Over a year ago

ok thank you - i see now ( having run it with commented out get and set methods) that they are not part of the flow.

tromgy · Accepted Answer · 2021-06-25 12:45:44Z

0

You're using 'appetizers' as the key here:

menu.addDishToCourse('appetizers', 'prawncocktail', 4.75);

, but the _courses object doesn't have it. You can change it to '_appetizers'.

answered Jun 25, 2021 at 12:45

tromgy

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