can't figure out with constructors javascript

Question

My code does not work correctly, I can not understand why. when you transfer the card to the shoop, he does not add money to it

   function Card (money=0) {
    this.money = money;
}

Card.prototype.addMoney = function(mon) {
  return this.money=this.money+mon;
}

 function CreditCard (money =0) {
this.money = money; 
}

 CreditCard.prototype = Object.create(Card.prototype);

function Shop (card) {
    this.card = card
    this.money=card.money;
    this.addMoney=this.card.addMoney;
}
Shop.prototype = Object.create(Card.prototype);


let card1 = new CreditCard(50);
card1.addMoney(10);//60
card1.addMoney(10);//70
let card2 = new Card(250);
let shop1 = new Shop(card1);
shop1.addMoney(10);//80 but don't work
console.log(card1.money);

Aplet123 · Accepted Answer · 2020-04-23 19:39:57Z

1

this.addMoney = this.card.addMoney;

This is the line with the issue. The function internally references this.money, but since the function is now inside the Shop class, this changes to refer to the shop. So, you have to bind the function to the card. The new line would be:

this.addMoney = this.card.addMoney.bind(this.card);

answered Apr 23, 2020 at 19:39

Aplet123

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Comments

Bergi · Accepted Answer · 2020-04-23 19:45:17Z

0

A shop is not a card. You should not use inheritance here. A shop has a card, so go for composition:

function Shop (card) {
    this.companyCard = card
}
Shop.prototype.addMoney = function(mon) {
    this.companyCard.addMoney(mon);
};
Shop.prototype.getMoney = function() {
    return this.companyCard.money;
};

answered Apr 23, 2020 at 19:45

Bergi

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