如何将变量用作对象内部的索引?(Javascript)

Question

我正试图使用变量prevente、main和dester作为数组的索引，但我不知道如何做到这一点。这是49号线。

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);

我已经尝试使用这个代码：

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

但这只是返回Object对象来代替索引号。

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dish对象。

一旦菜被退回，在generateRandomMeal中，您需要选择每个菜的name属性进行打印，并将所有price加起来得到总价：

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);

(总和后需要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。你现在的方式只是打印随机索引。

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());