Returning the numerical value property between two items

Question

I'm new to JS (first week) doing a command line card game for a school project. I've been able to get through the first three exercises (2 & 3 have been omitted).

However, I don't understand why I'm unable to access the property value from deck

I've looked around for a solution including here:

StackOverflow: compare two numeric String values

Medium (Nothing on comparing cards. PT2 includes HTML which we're not doing.): https://medium.com/@pakastin/javascript-playing-cards-part-1-ranks-and-values-a9c2368aedbd

Stack Overflow (this question was downvoted): How to compare 2 cards in a JavaScript card game

I am able to build the deck (Exercise 1):

function buildDeck() {
  const suits = ['spades', 'hearts', 'diamonds', 'clubs'];
  const ranks = ['A', '2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K'];
  const deck = [];
  for (let r = 0; r < ranks.length; r++) {
    for (let s = 0; s < suits.length; s++) {
      deck.push({ ranks: ranks[r], suits: suits[s], value: r + 1 });
    }
  }
  return deck;
}
console.log(buildDeck())

This returns the ranks, suits, and value for each card.

Next, I try to solve the problem of comparing the cards (Exercise 4):

const compare = (firstCard, secondCard) => {
  const cardValue = firstCard.value - secondCard.value;
  return cardValue;
}
console.log(compare());

However, when I try to return the value property of the first card minus the second card, I get the following error:

const cardValue = firstCard.value - secondCard.value;                              
TypeError: Cannot read property 'value' of undefined

If I remove .value from the code, I, of course, get NaN because there is not an object from the array to compare it with.

I'm stuck at this point and not sure how to get the difference between the cards. Any advice/help is greatly appreciated.

Nina Scholz · Answer 1 · 2019-06-02T20:47:44.820

You need to hand over cards as parameters.

Otherwise both parameters have the value undefined and this value is not an object.

const compare = (firstCard, secondCard) => {
//               ^^^^^^^^^  ^^^^^^^^^^    parameters


console.log(compare(card1, card2));
/                   ^^^^^  ^^^^^     insert cards for comparing

Just an example with a random drawing of two different cards and their comparison. The result could be a negative number. If that is not wanted, you could return an absolute value.

const compare = (firstCard, secondCard) => firstCard.value - secondCard.value;

function buildDeck() {
    const suits = ['spades', 'hearts', 'diamonds', 'clubs'];
    const ranks = ['A', '2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K'];
    const deck = [];
    for (let r = 0; r < ranks.length; r++) {
        for (let s = 0; s < suits.length; s++) {
            deck.push({ ranks: ranks[r], suits: suits[s], value: r + 1 });
        }
    }
    return deck;
}

var deck = buildDeck(),
    card1 = deck[Math.floor(Math.random() * deck.length)],
    card2;

do {
    card2 = deck[Math.floor(Math.random() * deck.length)];
} while (card1 === card2)

console.log(card1);
console.log(card2);
console.log(compare(card1, card2)); // <---- here hand over the two cards for comparing

.as-console-wrapper { max-height: 100% !important; top: 0; }

Thanks for replying. I guess the problem I'm having is that I don't understand exactly what I am supposed to hand over as parameters. I add `arguments` in the 'console log' which gives me a result but I don't know how to get a number from `.value` in the `deck` function — Noble Polygon, Jun 02 '19 at 20:30
Thanks! I'm going to study the logic you implemented. Have a great week! — Noble Polygon, Jun 02 '19 at 21:02

Returning the numerical value property between two items

1 Answers1