</> Michael Burrows

Create a random playing card generator with JavaScript

Last modified on September 3rd 2020 GitHub [Source] CodePen [Demo]

In this tutorial we’ll be using JavaScript to generate a deck of playing cards and then select a random card from that deck. We’ll then output the random card in the browser and add some CSS so it looks like an actual playing card. If you’re interested in building card games using JavaScript this is a good starting point before moving onto more elaborate games.

Let’s get started by creating a index.html file with the following markup:

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>Random Playing Card</title> <link rel="stylesheet" href="style.css" /> </head> <body> <script src="script.js"></script> </body> </html>

Then create a script.js file and add a deckBuilder function that we’ll use to generate an array containing the values for 52 playing cards:

function deckBuilder() { // ... }

Inside deckBuilder define the values and suits used in a deck of playing cards:

const values = [ "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", ]; const suits = ["Hearts", "Diamonds", "Spades", "Clubs"];

Next loop through the suits array whilst also looping through the values array and push the combined data into the cards array:

const cards = []; for (let s = 0; s < suits.length; s++) { for (let v = 0; v < values.length; v++) { const value = values[v]; const suit = suits[s]; cards.push({ value, suit }); } } return cards;

We now have a function that creates an array with the suit/value combination for 52 playing cards structured as follows:

0: {value: "A", suit: "Hearts"} 1: {value: "2", suit: "Hearts"} 2: {value: "3", suit: "Hearts"}

Next we’ll create the randomCard function and pass it the cards array:

function randomCard(cards) { // ... } const cards = deckBuilder(); randomCard(cards);

Inside the randomCard function we’ll generate a random number between 0 and 51 (not 52 as array indexes start at 0) and get the data from the cards array at that index. This data is then stored in variables to make it easier to work with later:

const random = Math.floor(Math.random() * 51); const cardValue = cards[random].value; const cardSuit = cards[random].suit;

As there are HTML character entities for each of the playing card suits (♥/♦/♠/♣) we can output these onto our playing card without having to use images. Because the entity code for diamonds is truncated we need to also truncate the "Diamonds" string, the other suits entity codes match the strings (&hearts; &spades; &clubs;) so all we need todo is convert them to lowercase.

let entity; cardSuit === "Diamonds" ? (entity = "&diams;") : (entity = "&" + cardSuit.toLowerCase() + ";");

Finally we can render the random card into the HTML page. If you look at the final design for this project you’ll see why cardValue and entity have been repeated.

const card = document.createElement("div"); card.classList.add("card", cardSuit.toLowerCase()); card.innerHTML = '<span class="card-value-suit top">' + cardValue + entity + '</span>' + '<span class="card-suit">' + entity + '</span>' + '<span class="card-value-suit bot">' + cardValue + entity + '</span>'; document.body.appendChild(card);

With the functionality complete we can add some CSS to our random playing card.

Create a file called style.css and add the following to create the basic playing card shape:

.card { position: relative; width: 105px; height: 150px; border-radius: 5px; border: 1px solid #ccc; box-shadow: 0px 0px 5px 0px rgba(0,0,0,0.25); }

Because .card is positioned relatively we can use absolute positioning for the top and bottom text. We’ll also rotate the text at the bottom 180 degrees just like a real playing card.

.card-value-suit { display: inline-block; position: absolute; } .card-value-suit.top { top: 5px; left: 5px; } .card-value-suit.bot { transform: rotate(180deg); bottom: 5px; right: 5px; } .card-suit { font-size: 50px; position: absolute; top: 50%; transform: translateY(-50%); left: 25%; }

And finally we’ll add the colors for each of the suits:

.card.spades, .card.clubs { color: black; } .card.hearts, .card.diamonds { color: red; }