Deck

Deck is a basic JavaScript implementation of a deck of cards. An interface is provided to shuffle, pick, draw, re-insert and observe cards within the deck in a variety of ways. Deck makes no assumptions about the type of objects that will be contained within a deck: it can be used equally well with a string representation of traditional playing cards (say, 'h4' for the 4 of hearts) as it could with a complex object instantiating a custom constructor (e.g. a MagicCard object).

There are many implementations of this behavior on npm; I created another as an experiment for myself, not out of any fault in the existing options.

Installation

Install with NPM: npm install card-deck

Creating & Using a Deck

Configure the deck

To create a deck object, instantiate it from the Deck constructor:

var myDeck = new Deck();

To set the cards that this deck will contain, either provide an array argument when calling the Deck constructor,

var myDeck = new Deck([ card1, card2, card3/*, ... */ ]);

or else call the .cards method to explicitly specify the cards this deck instance will contain:

var myOtherDeck = new Deck();
myOtherDeck.cards([ card1, card2, card3/*, ... */ ]);

The cards will be initially inserted in the same order in which they occur in the provided array. To randomize the order of the cards, call .shuffle:

myDeck.shuffle();

This will shuffle the cards using the Fisher-Yates Shuffle algorithm. For more background on this technique, see Mike Bostock's visual comparison of shuffle algorithms.

Inspect the Deck

To observe cards within the deck without removing them from the deck, use the .top, .bottom and .random methods:

// Return the card at the top of the deck
var topCard = myDeck.top();

// Return the bottom two cards in the deck
var bottomCards = myDeck.bottom(2);

// Return six random cards anywhere in the deck
var randomCards = myDeck.random(6);

Retrieve the count of cards currently contained within the deck by using the .remaining method:

var cardCount = myDeck.remaining(); // 42

Draw Cards from the Deck

Remove cards from the deck (and return them as an object or array) using any of the draw methods:

// Draw a single card
var drawnCard = deck.draw();

// Draw 5 cards
var hand = deck.draw(5);

// Draw a card from the bottom of the deck
var bottomCard = deck.drawFromBottom();

// Draw 3 cards where the card object's `.suit` is "hearts"
var threeHearts = deck.drawWhere(function(card) {
  return card.suit === 'hearts';
}, 3);

// Draw 2 random cards from anywhere in the deck
var randomCards = deck.drawRandom(2);

Add Cards to the Deck

Return cards to the deck using the following discard methods:

// Place a card on the top of the deck
myDeck.addToTop({ suit: 'spades', rank: 'Jack' });

// Return two cards to the bottom of the deck
myDeck.addToBottom([card1, card2]);

// Return three cards to the bottom of the deck in random order
myDeck.shuffleToBottom([card1, card2, card3]);

// Return two cards to the top of the deck in random order
myDeck.shuffleToTop([card1, card2]);

// Insert an array of cards at random positions throughout the deck
myDeck.addRandom([card1, card2, card3]);

The verbiage here is intentionally general. You can create your own aliases for these functions by augmenting the Deck prototype:

myDeck.prototype.replace = function( cards ) {
  return this.placeOnTop( cards );
}

Development & Contributing

Deck is intentionally minimal, but if you have a suggestion for a new feature or (most importantly!) a bug report about something that isn't working right, please open an issue so that we can address the problem quickly.

If you are interested in altering or adding code to Deck, here is how to work with the repository locally:

1. Ensure you have Node.js installed on your system: on OSX, we recommend using Homebrew to install Node.
2. Clone this project to your computer
3. On the command line, within the directory to which you cloned this project, run npm install to install the development dependencies. Deck has no run-time dependencies.

All Deck code is unit tested. Execute

npm test

to run the tests and view a code coverage summary. More detailed code coverage information will now be available in the coverage/ directory.

To run the unit tests as a watcher, so that they will re-run when code changes, execute the command

npm run test:watch

In a similar manner, to run the tests through code syntax & style validation with JSHint and JSCS, use the command

npm run lint

to run once and

npm run lint:watch

to run many times.