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JavaScript

Posted by Kristian Woods
Kristian Woods
23,414 Points

How do you remove duplicate items from an Set in Javascript?

I'm trying to generate 52 playing cards at random.

I have a constructor that create a newCard object. Each object is assigned a random number between 2-10 and a suit.

I then use a While loop to generate the newCard object 52 times. However, I'm generating duplicate cards. How can I resolve this? I tried using a javascript Set() opposed to an array, because I thought it wouldn't duplicate the cards.

Also, it would be really apprecatied it someone could comment on my code, and suggest an alternative to refactor the code.

Thanks

Code below:

Constructor function:

class PlayingCard {
    constructor(number, suit) {
        this.suit = suit;
        this.number = number;
    }

    get cardInfo() {
        return `The Card is the ${this.number} of ${this.suit}`;
    }
}

Random Number(rN) generator (2-10):

let ranNumber = () => {
    let rN = Math.floor(Math.random() * 10) + 1;
    if(rN == 1) {
        rN += 1;
    } else if(rN == 11) {
        rN -= 1;
    }
    return rN;
};

Suit Array and While loop:

const suitArray = [
    'Hearts',
    'Diamonds',
    'Clubs', 
    'Spades'
];

let randomSuit = () => suitArray[Math.floor(Math.random()*suitArray.length)];

let cardSet = new Set();

let i = 52;

while(i) {
    let newCard = new PlayingCard(ranNumber(), randomSuit());
    cardSet.add(newCard);
    paragraph(newCard.cardInfo);
    i--;
}

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

Sets require unique entries, but the test for equality on an object is actually a test for identity. Two different objects with the same properties are still considered not equal.

You could use a loop to remove duplicates, but then you "won't be playing with a full deck". :laughing:

If you really want a deck of cards, why not just generate them in a non-random way?

for (suit of suitArray)
  for (number = 1; number <= 13; number++)
    cardSet.add(new PlayingCard(number, suit));

Note: I extended the numbers to include 1 (ace) and 11-13 (jack, queen, king).