当我保存方法的返回时，它保存未定义

Question

I've recently started learning JS and in this problem I have to do two methods, the first one creates an array with the cars that haven't been sold yet and the second has to create an array with the cars that haven´t been sold yet and are 0 km. I have to use the first method in the second one, but when I save the return of the first method it saves UNDEFINED. Thanks

let cars = require('./cars');

let concessionaire = {
  cars: cars,

  carsForSell: function() {
    let carsNotSold = [];
    for (let i = 0; i < this.cars.length; i++) {
      if (this.cars[i].sold == false) {
        carsNotSold.push(this.cars[i]);
      }
    }
    return carsNotSold;
  },

  newCars: function() {
    let aux = this.carsForSell();
    let zeroKm = [];
    for (let i = 0; i < this.cars.length; i++) {
      if (this.aux[i].km < 100) {
        zeroKm.push(aux[i]);
      }
    }
    return zeroKm;
  }
};

The structure of cars is

let firstCar = {
    brand: 'Ford',
    model: 'Fiesta',
    price: 150000,
    km: 200,
    color: 'Blue',
    dues: 12,
    year: 2019,
    patent: 'APL123',
    sold: false
};

let secondCar = {
    brand: 'Toyota',
    model: 'Corolla',
    price: 100000,
    km: 0,
    color: 'White', 
    dues: 14,
    year: 2019,
    patent: 'JJK116',
    sold: false
};

let cars = [firstCar, secondCar];

module.exports = cars;

Answer 1

The method are correct, you have an additional this in your code:

 if(this.aux[i].km < 100){

aux is a local variable, this is wrong.

Working version:

 let firstCar = { brand: 'Ford', model: 'Fiesta', price: 150000, km: 200, color: 'Blue', dues: 12, year: 2019, patent: 'APL123', sold: false }; let secondCar = { brand: 'Toyota', model: 'Corolla', price: 100000, km: 0, color: 'White', dues: 14, year: 2019, patent: 'JJK116', sold: false }; let cars = [firstCar, secondCar]; let concessionaire = { cars: cars, carsForSell: function(){ let carsNotSold = []; for (let i = 0; i < this.cars.length; i++){ if(this.cars[i].sold == false){ carsNotSold.push(this.cars[i]); } } return carsNotSold; }, newCars: function(){ let aux = this.carsForSell(); let zeroKm = []; for (let i = 0; i < this.cars.length; i++){ if(aux[i].km < 100){ zeroKm.push(aux[i]); } } return zeroKm; } }; console.log(concessionaire.newCars())

Answer 2

When you declared "concessionaire" there is no variable "cars".

If you use let and const scope. you have to write cars first, so that "concessionaire" can use that value.