In this post, I will be going over how to build a deck of cards in JavaScript, that can be used for future projects or future games, such as this JavaScript Blackjack game. This is a super quick implementation, and can be done in less than 100 lines of code. I will be implementing as many card related functions/features as I can, such as shuffling a deck, grabbing a card from the top or bottom and creating a new deck of cards.
If you are new to JavaScript, then I recommend the following book Web Design with HTML, CSS, JavaScript and jQuery, which can get you up and running pretty quickly with JavaScript.
Project: Deck of cards
Language: JavaScript
Estimated Completion: 30 minutes
Overview
A deck of traditional playing cards is composed of 4 sets of 13 sequential numbered cards. A, 2, 3, 4, 5, 6, 7, 8, 9, 10, J, Q, and K. Each card in the set belongs to a particular suit: Hearts, Spades, Clubs and Diamonds. The deck will consist of an Array of objects with a function to render each card graphically.
Variable declarations
Declare the following variables in order to get started.
var suits = ["spades", "diamonds", "clubs", "hearts"];
var values = ["A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"];
The variable suits is an array of card suites that we will use as a lookup table. And our 2nd variable values will hold all the possible values that a card can have.
Create The Deck
In order to create the deck, we're going to pair up each suit from the array above, with each possible value also from the array declared above. We're going to create a new card Object with the corresponding value and suit and that object will be added that to the deck array.
The getDeck() function will return this brand new deck to the caller.
function getDeck()
{
var deck = new Array();
for(var i = 0; i < suits.length; i++)
{
for(var x = 0; x < values.length; x++)
{
var card = {Value: values[x], Suit: suits[i]};
deck.push(card);
}
}
return deck;
}
This function will populate the deck array with 52 card objects, which will resemble the following at the end.
var deck = [{Value: 'A', Suit: 'Spades'}, {Value: 'A', Suit: 'Diamonds'}, {Value: 'A', Suit: 'Clubs'}...]
Shuffling the card deck
Next up we need a function to shuffle the deck. For this, we will need to come up with a shuffling algorithm. We are going to pick 2 random locations on the deck, and then switch their values around. We will be doing this about 1000 times per shuffle, which should be good enough to generate a seemingly random deck.
function shuffle(deck)
{
// for 1000 turns
// switch the values of two random cards
for (var i = 0; i < 1000; i++)
{
var location1 = Math.floor((Math.random() * deck.length));
var location2 = Math.floor((Math.random() * deck.length));
var tmp = deck[location1];
deck[location1] = deck[location2];
deck[location2] = tmp;
}
}
At this point, the deck array should contain 52 objects in a random order. But it's funner to see it than to hear me talk about it, so my next trick, I'm going to make the cards appear.
function renderDeck(deck)
{
document.getElementById("deck").innerHTML = "";
for(let i = 0; i < deck.length; i++)
{
let card = document.createElement("div");
let value = document.createElement("div");
let suit = document.createElement("div");
card.className = "card";
value.className = "value";
suit.className = "suit " + deck[i].Suit;
value.innerHTML = deck[i].Value;
card.appendChild(value);
card.appendChild(suit);
document.getElementById("deck").appendChild(card);
}
}
For this example, our card will simply be a <div> with a particular class specifying its suit. It will use the following sprite image.
At this point, we have the functions to create a new deck of cards, shuffle them, and draw them out onto the screen. It looks something like the following.
Version 2: Rendering
A cleaner way render the cards (at least to me) is a method that I used in my blackjack game, in which I use HTML entities instead of images.
function renderDeck(deck)
{
document.getElementById('deck').innerHTML = '';
for(var i = 0; i < deck.length; i++)
{
var card = document.createElement("div");
var icon = '';
if (deck[i].Suit == 'hearts')
icon='?';
else if (deck[i].Suit == 'spades')
icon = '?';
else if (deck[i].Suit == 'diamonds')
icon = '?';
else
icon = '?';
card.innerHTML = deck[i].Value + '' + icon;
card.className = 'card';
document.getElementById("deck").appendChild(card);
}
}
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Putting it together
Now that we have all of the helper and primary functions setup, we can see how it all comes together.
Creating a new deck
The getDeck() function created above will return a brand new 52-card deck whenever you need one. You can store that in a local variable (or global) depending on your project.
var deck1 = getDeck();
var deck2 = getDeck();
Once the decks are created they can be passed into the remaining helper functions as needed.
var deck1 = getDeck();
shuffle(deck1);
renderDeck(deck1);
Download full source code