Logichess NPM | npm.io

logichess

logichess is a TypeScript library that provides a set of classes to handle chess game logic. It can be used to create custom chess games, validate moves, get legal moves, and other useful functionalities related to chess.

Installation

To install logichess, you need to have npm installed. Then run the following command:

npm i logichess

Usage

To use logichess in your TypeScript or JavaScript project, import the module using either CommonJS or ES6 import syntax.

// Common JS
const { Chess } = require("logichess");
// ES Module
import { Chess } from "logichess";

Creating a new game

You can create a new game by simply initializing a new instance of the Chess class:

const game = new Chess();

This will create a new game with the default starting position.

Alternatively, you can create a custom game by passing a FEN string to the constructor:

const fenString =
  "r1bqkb1r/pppp1ppp/2n2n2/4p1N1/2B1P3/8/PPPP1PPP/RNBQK2R b KQkq - 5 4";
const customGame = new Chess(fenString);

Retrieving game information

Once you have a Chess instance, you can retrieve information about the game state by accessing its properties:

console.log(game.data);

Which will log the following data:

{
  status: 'normal',
  difference: 0,
  turn: 'w',
  fen: 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1',
  board: [
    ["r", "n", "b", "q", "k", "b", "n", "r"],
    ["p", "p", "p", "p", "p", "p", "p", "p"],
    [".", ".", ".", ".", ".", ".", ".", "."],
    [".", ".", ".", ".", ".", ".", ".", "."],
    [".", ".", ".", ".", ".", ".", ".", "."],
    [".", ".", ".", ".", ".", ".", ".", "."],
    ["P", "P", "P", "P", "P", "P", "P", "P"],
    ["R", "N", "B", "Q", "K", "B", "N", "R"],
  ],
  moves: [
    {
      from: { rank: 6, file: 0 },
      to: { rank: 4, file: 0 },
      piece: 'P',
      faction: 'w',
      san: 'a4',
      lan: 'a2a4',
      uci: 'a2a4',
      fenResult: 'rnbqkbnr/pppppppp/8/8/P7/8/1PPPPPPP/RNBQKBNR b KQkq a3 0 1'
    },
    {
      from: { rank: 6, file: 0 },
      to: { rank: 5, file: 0 },
      piece: 'P',
      faction: 'w',
      san: 'a3',
      lan: 'a2a3',
      uci: 'a2a3',
      fenResult: 'rnbqkbnr/pppppppp/8/8/8/P7/1PPPPPPP/RNBQKBNR b KQkq - 0 1'
    },
    // ... more moves below
  ]
}

This will log an object containing the following properties:

status - the status of the game ("normal", "check", "end")
difference - the difference in material value between the two sides
turn - the side to move ("w" for white, "b" for black)
fen - the FEN string representing the current position
board - a two-dimensional array representing the current position on the board
moves - an array containing all legal moves in the current position

Making a move

To make a move, call the play method on the Chess instance, passing the move in either SAN, LAN, or UCI format as a string:

// using SAN
game.play("e4");
// using LAN
game.play("e2e4");
// using UCI
game.play("e2-e4");

You can also pass a Move object as the parameter:

game.play({
  from: { rank: 6, file: 4 },
  to: { rank: 4, file: 4 },
  piece: "P",
  faction: "w",
  san: "e4",
  lan: "e2e4",
  uci: "e2e4",
  fenResult: "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1",
});

To learn more about the Move object, read the source file.

The play method will update the game state with the new position resulting from the move. If the move is not legal, an exception will be thrown.