Poker Hand Evaluator

A collection of useful functions for determining the strongest possible hand given a coordination of cards (hole cards & community cards), the strongest effective hand when comparing two hands, and the probability of winning the hand given what cards are known.

Usage

Types

The following types are defined & utilized by this package.

• EvaluatedHand: An object representing the effective hand & strength, given a coordination of cards.
• Odds: An object representing how a hand will perform given a scenario. Includes the number of wins, ties, and total possible outcomes.

Core Functions

evaluate

Given a list of hole cards and (optionally) community cards, determine the best possible poker hand and the strength of that hand.

import { evaluate } from '@poker-apprentice/hand-evaluator';
import { HandStrength } from '@poker-apprentice/types';

const result = evaluate({
  holeCards: ['As', 'Qd'],
  communityCard: ['Js', 'Kc', 'Td'],
});

console.log(result);
// => { hand: ['As', 'Kc', 'Qd', 'Js', 'Td'], strength: 6 };

console.log(result.strength === HandStrength.Straight);
// => true

Note that the evaluate does not require 5 cards to determine the best hand. The best hand possible with fewer cards or more cards can be determined as well.

console.log(evaluate({ holeCards: ['As', 'Ad'] }));
// => { hand: ['As', 'Ad'], strength: 9 };

console.log(
  evaluate({
    holeCards: ['9s', '8s'],
    communityCards: ['5d', '6d', '6c', '7c', '2h'],
  }),
);
// => { hand: ['9s', '8s', '7c', '6d', '5d'], strength: 6 };

By default, the evaluate function allows any number of hole cards or community cards to be used when determining the best possible poker hand. If a specific number of hole cards must be used (e.g.: exactly 2 cards in Omaha or up to 2 cards in Pineapple), then the minimumHoleCards and maximumHoleCards options can be provided.

const omahaHand = evaluate({
  holeCards: ['As', 'Kd', 'Td', '2s'],
  communityCards: ['Js', '4s', '3d', '5d', 'Ah'],
  minimumHoleCards: 2,
  maximumHoleCards: 2,
});
console.log(omahaHand);
// => { hand: ['5d', '4s', '3d', '2s', 'As'], strength: 6 }

const pineappleHand = evaluate({
  holeCards: ['Jc', 'Tc', '7d'],
  communityCards: ['9h', '8c', '2d'],
  maximumHoleCards: 2,
});
console.log(pineappleHand);
// => { hand: ['Jc', 'Tc', '9h', '8c', '2d'], strength: 10 }

compare

Given two evaluated hands, returns -1, 0, or 1 to represent the stronger hand.

import { compare, evaluate } from '@poker-apprentice/hand-evaluator';

const hand1 = evaluate({ holeCards: ['9s', '8s', '5d', '6d', '6c', '7c', '2h'] });
const hand2 = evaluate({ holeCards: [] });
const result = compare(hand1, hand2);

console.log(result);
// => -1

This function can be used to sort any number of hands in an array.

import { compare, evaluate } from '@poker-apprentice/hand-evaluator';

const communityCards = ['Qs', 'Js', '7d'];
const result = [
  evaluate({ holeCards: ['As', 'Qd'], communityCards }),
  evaluate({ holeCards: ['Ac', 'Tc'], communityCards }),
  evaluate({ holeCards: ['9s', '8s'], communityCards }),
].sort(compare);

simulate (alias: oddsAsync)

Given a list of hands and community cards, estimate how often each hand will win or tie using a Monte Carlo simulation for roughly estimating the odds of a hand winning or tying.

The simulate generator function returns a generator that can be used to run as many Monte Carlo simulations as desired, limited by the maximum number of simulations that are possible for a given scenario based upon the provided inputs. (For example, if there are only 2 streets remaining to be dealt with 45 cards remaining in the deck, then there are 45 * 44 = 1,980 possible simulations.)

import { Hand, simulate } from '@poker-apprentice/hand-evaluator';

const hand1: Hand = ['As', 'Ks'];
const hand2: Hand = ['Jd', 'Jh'];

const generate = simulate({
  allHoleCards: [hand1, hand2],
  communityCards: ['Qd', 'Js', '8d'],
  expectedCommunityCardCount: 5,
  expectedHoleCardCount: 2,
  minimumHoleCardsUsed: 0,
  maximumHoleCardsUsed: 2,
});

let result = generate.next();
while (!result.done) {
  const hand1WinPercent = ((result[0].wins / result[0].total) * 100).toFixed(1);

  // Output the cumulative results every 500 runs.
  if (result[0].total % 500 === 0) {
    console.log(hand1WinPercent, result);
  }

  result = generate.next();
}

// => "13.8" [{ wins: 69, ties: 0, total: 500 }, { wins: 431, ties: 0, total: 500 }]
// => "13.9" [{ wins: 139, ties: 0, total: 1000 }, { wins: 861, ties: 0, total: 1000 }]
// => "15.4" [{ wins: 231, ties: 0, total: 1500 }, { wins: 1269, ties: 0, total: 1500 }]
// => "14.8" [{ wins: 295, ties: 0, total: 2000 }, { wins: 1705, ties: 0, total: 2000 }]

odds

Given a list of hands and community cards, determine how often each hand will win or tie.

Note: The implementation for this is exhaustive, and it is not practical for scenarios missing more than about 1-2 cards worth of data. It is strongly suggested that the simulate function be used instead.

import { Hand, odds } from '@poker-apprentice/hand-evaluator';

const hand1: Hand = ['As', 'Ks'];
const hand2: Hand = ['Jd', 'Jh'];

const result = odds([hand1, hand2], {
  communityCards: ['Qd', 'Js', '8d'],
  expectedCommunityCardCount: 5,
  expectedHoleCardCount: 2,
  minimumHoleCardsUsed: 0,
  maximumHoleCardsUsed: 2,
});

console.log(result);
// => [
//      { wins: 304, ties: 0, total: 1980 },
//      { wins: 1676, ties: 0, total: 1980 },
//    ]

Helper Functions

In addition to the core functions, there are some poker game-specific functions that wrap these core functions for ease of use. These functions are effectively the same as calling the evaluate of odds function directly with the appropriate option values prepopulated.

The functions also perform appropriate error checking/throwing to ensure that the holeCards and communityCards are of the correct length for each game.

evaluateHoldem

Evaluates a hand of Texas Hold'em.

import { evaluateHoldem } from '@poker-apprentice/hand-evaluator';
const hand = evaluateHoldem({
  holeCards: ['As', 'Kd'],
  communityCards: ['9h', '8d', '2c'],
});

evaluateOmaha

Evaluates a hand of Omaha.

import { evaluateOmaha } from '@poker-apprentice/hand-evaluator';
const hand = evaluateOmaha({
  holeCards: ['Jc', 'Qd', '4h', '7c'],
  communityCards: ['2c', 'Qs', '4c'],
});

evaluatePineapple

Evaluates a hand of Pineapple.

import { evaluatePineapple } from '@poker-apprentice/hand-evaluator';
const hand = evaluatePineapple({
  holeCards: ['Jc', '7h', 'Qh'],
  communityCards: ['9h', '8d', '2c', '3h', 'Td'],
});

evaluateStud

Evaluates a hand of Stud.

import { evaluateStud } from '@poker-apprentice/hand-evaluator';
const hand = evaluateStud({ holeCards: ['As', 'Kd', 'Ks', '8s', 'Ac', 'Kh', '4d'] });

oddsHoldem

Calculates the odds of winning or tying a hand of Texas Hold'em.

import { oddsHoldem } from '@poker-apprentice/hand-evaluator';
const allHoleCards = [
  ['As', 'Kd'],
  ['Ks', '8s'],
];
const communityCards = ['Ts', 'Qs', 'Jd'];
const result = oddsHoldem(allHoleCards, communityCards);

oddsOmaha

Calculates the odds of winning or tying a hand of Omaha.

import { oddsOmaha } from '@poker-apprentice/hand-evaluator';
const allHoleCards = [
  ['As', 'Kd', 'Td', 'Tc'],
  ['Ks', '8s', '9h', 'Kc'],
];
const communityCards = ['Ts', 'Qs', 'Jd'];
const result = oddsOmaha(allHoleCards, communityCards);

oddsPineapple

Calculates the odds of winning or tying a hand of Pineapple.

import { oddsPineapple } from '@poker-apprentice/hand-evaluator';
const allHoleCards = [
  ['As', 'Kd', 'Td'],
  ['Ks', '8s', 'Kc'],
];
const communityCards = ['Ts', 'Qs', 'Jd'];
const result = oddsPineapple(allHoleCards, communityCards);

oddsStud

Calculates the odds of winning or tying a hand of Stud.

import { oddsStud } from '@poker-apprentice/hand-evaluator';
const allHoleCards = [
  ['As', 'Kd', 'Ks', '8s', 'Ac'],
  ['9s', '8s', 'Ts', '6s', '4h'],
];
const result = oddsStud(allHoleCards);

simulateHoldem (alias: oddsHoldemAsync)

Estimates the odds of winning or tying a hand of Texas Hold'em.

import { simulateHoldem } from '@poker-apprentice/hand-evaluator';
const abort = simulateHoldem({
  allHoleCards: [
    ['As', 'Kd'],
    ['Ks', '8s'],
  ],
  communityCards: ['Ts', 'Qs', 'Jd'],
  callback: (result) => console.log(result),
});

simulateOmaha (alias: oddsOmahaAsync)

Estimates the odds of winning or tying a hand of Omaha.

import { simulateOmaha } from '@poker-apprentice/hand-evaluator';
const abort = simulateOmaha({
  allHoleCards: [
    ['As', 'Kd', 'Td', 'Tc'],
    ['Ks', '8s', '9h', 'Kc'],
  ],
  communityCards: ['Ts', 'Qs', 'Jd'],
  callback: (result) => console.log(result),
});

simulatePineapple (alias: oddsPineappleAsync)

Estimates the odds of winning or tying a hand of Pineapple.

import { simulatePineapple } from '@poker-apprentice/hand-evaluator';
const abort = simulatePineapple({
  allHoleCards: [
    ['As', 'Kd', 'Td'],
    ['Ks', '8s', 'Kc'],
  ],
  communityCards: ['Ts', 'Qs', 'Jd'],
  callback: (result) => console.log(result),
});

simulateStud (alias: oddsStudAsync)

Estimates the odds of winning or tying a hand of Stud.

import { simulateStud } from '@poker-apprentice/hand-evaluator';
const abort = simulateStud({
  allHoleCards: [
    ['As', 'Kd', 'Ks', '8s', 'Ac'],
    ['9s', '8s', 'Ts', '6s', '4h'],
  ],
  callback: (result) => console.log(result),
});

Development

Contributions are welcome. Please create an issue in the project first to discuss any possible enhancements, bugs, or other changes prior to submitting a pull request. Alternatively, browse existing issues if interested in providing a fix.

Environment Setup

1. Install yarn and git.
2. Clone this repository: git clone [email protected]:poker-apprentice/hand-evaluator.git
3. Install dependencies: yarn install

Run tests

To run the full test suite:

yarn test

To run a specific test:

yarn test compare.test.ts           # matches test file name
yarn test -t "compare"              # matches test name/description

NOTE: Profiling is disabled until Node v20 is supported, per this GitHub issue.

To run tests and run profiler:

yarn test:profile                   # runs full test suite
yarn test:profile compare.test.ts   # matches test file name
yarn test:profile -t "compare"      # matches test name/description

This will create one .cpuprofile file per test under the profiles/ folder. To open these files in Google Chrome:

1. Navigate to [chrome://inspect].
2. Click "Open dedicated DevTools for Node".
3. Select the "Profiler" tab.
4. Click the "Load" button, and select your file.

To remove old .cpuprofile files:

yarn clean

Run linter

yarn lint

Run formatter

yarn format

Build package

yarn build