holdem.js

const R = require('ramda');

const NUM_CARDS_IN_DECK = 52;
const NUM_CARDS_PER_PLAYER = 2;
const NUM_PLAYERS = 2;

const possibleValues = [
  '2', '3', '4', '5', '6', '7', '8', '9',
  '10', 'J', 'Q', 'K', 'A'
];
const possibleSuits = ['♣', '♠', '♥', '♦'];
const cards = R.xprod(possibleValues, possibleSuits);

const getRandomIndex = max => Math.floor(Math.random() * max);

const shuffle = deck => {
  let deckToTakeFrom = R.clone(deck);
  let shuffled = [];

  while (shuffled.length < NUM_CARDS_IN_DECK) {
    let cardIdx = getRandomIndex(deckToTakeFrom.length);
    let card = R.nth(cardIdx, deckToTakeFrom);
    deckToTakeFrom = R.remove(cardIdx, 1, deckToTakeFrom);
    shuffled.push(card);
  }

  return shuffled;
};

// setup
let shuffledCards = shuffle(cards);
let currentHands = [...new Array(NUM_PLAYERS)].map(hand => []);

// deal
while (shuffledCards.length > (NUM_CARDS_IN_DECK - (NUM_CARDS_PER_PLAYER * NUM_PLAYERS))) {
  currentHands = currentHands.map(hand => {
    let cardIdx = getRandomIndex(shuffle.length);
    let card = R.nth(cardIdx, shuffledCards);
    shuffledCards = R.remove(cardIdx, 1, shuffledCards);
    return R.append(card, hand);
  });
}

let state = {
  hands: currentHands,
  deck: shuffledCards,
  round: 1,
  table: [],
  discard: []
};

// play
const discardOneCard = state => {
  const cardIdx = getRandomIndex(state.deck.length);
  const discard = R.nth(cardIdx, state.deck);
  // remove the discard from the deck
  // add it to the discard pile
  state = R.assoc('deck', R.remove(cardIdx, 1, state.deck), state);
  return R.assoc('discard', R.append(discard, state.discard), state);
};
const dealTable = state => {
  let numCardsToDeal = 1;
  if (state.round === 1) { // flop
    numCardsToDeal = 3;
  }

  while (numCardsToDeal > 0) {
    const cardIdx = getRandomIndex(state.deck.length);
    const card = R.nth(cardIdx, state.deck);
    state = R.assoc('deck', R.remove(cardIdx, 1, state.deck), state);
    state = R.assoc('table', R.append(card, state.table), state);

    numCardsToDeal--;
  }

  return state;
};
const showBoard = state => {
  console.log('Player 1:\t', state.hands[0][0][0] + state.hands[0][0][1], state.hands[0][1][0] + state.hands[0][1][1]);
  console.log('Player 2:\t', state.hands[1][0][0] + state.hands[1][0][1], state.hands[1][1][0] + state.hands[1][1][1]);
  console.log();
  console.log('Table:\t', state.table.reduce((prev, curr) => prev += curr[0] + curr[1] + ' ', ''));
  return state;
};

const finishRound = state => R.assoc('round', state.round + 1, state);

while (state.round <= 3) {
  state = R.pipe(
    discardOneCard,
    dealTable,
    showBoard,
    finishRound
  )(state);
}