JavaScript 错误：无法读取未定义的属性“推送”

   let menu = {
        _courses: {
            appetizers: [],
            mains: [],
            desserts: [],
            get appetizers() {
                return this.appertizers;
            },
            set appetizers(newAppetizer) {
                this.appetizers = newAppetizer;
            },
            get mains() {
                return this.mains
            },
            set mains(newMain) {
                this.mains = newMain;
            },
            get desserts() {
                return this.desserts;
            },
            set desserts(newDessert) {
                this.desserts = newDessert;
            },
        },
        get courses() {
            return {
                appetizers: this._courses.appetizers,
                mains: this._courses.mains,
                desserts: this._courses.desserts
            };
        },
    
        addDishToCourse(courseName, dishName, dishPrice) {
            const dish = {
                name: dishName,
                price: dishPrice,
            };
    
            this._courses[courseName].push(dish);
        },
    
        getRandomDishFromCourse(courseName) {
            const dishes = this._courses[courseName];
            const randomIndex = Math.floor(Math.random() * dishes.length);
            return dishes[randomIndedx];
        },
        generateRandomMeal() {
            const appetizer = this.getRandomDishFromCourse("appetizers");
            const main = this.getRandomDishFromCourse("mains");
            const dessert = this.getRandomDishFromCourse("desserts");
            const totalPrice = appetizer.price + main.price + dessert.price;
            return `Your meal is ${appetizer.name}, ${main.name}, ${dessert.name}. Your total is $${totalPrice}.`
        }
    
    }
    
    
    menu.addDishToCourse('appetizers', 'Ceasar Salad', 4.25);
    menu.addDishToCourse('appetizers', 'Prawn Coctail', 4.25);
    menu.addDishToCourse('appetizers', 'Garlic Bread', 3.50);
    
    menu.addDishToCourse('mains', 'Lasagna', 9.75);
    menu.addDishToCourse('mains', 'Ribeye Steak', 14.95);
    menu.addDishToCourse('mains', 'Fish & Chips', 12.95);
    
    menu.addDishToCourse('desserts', 'Cheese Cake', 4.50);
    menu.addDishToCourse('desserts', 'Creme Brule', 4.25);
    menu.addDishToCourse('desserts', 'Cheese Board', 3.25);
   
let meal = menu.generateRandomMeal();

console.log(meal);