chess.js

Install the most recent version of chess.js from the NPM registry using the following command:

npm install chess.js

You can use the Chess class to manage game state, generate valid moves, and detect game over conditions. The following example demonstrates how to instantiate a new game, loop through valid moves randomly until the game ends, and output the final game in PGN format.

import { Chess } from 'chess.js'

const chess = new Chess()

while (!chess.isGameOver()) {
  const moves = chess.moves()
  const move = moves[Math.floor(Math.random() * moves.length)]
  chess.move(move)
}
console.log(chess.pgn())

Use the move() method to execute a move. The method accepts several formats:

• A SAN (Standard Algebraic Notation) string (e.g., 'e4').
• An object specifying { from, to, promotion }.
• null (to represent a null move).

You can pass an optional { strict: boolean } configuration object. If strict is true, the move must be valid according to chess rules.

Create a new instance of the Chess class to manage a chess game. You can optionally provide an initial FEN (Forsyth-Edwards Notation) string.

Use the skipValidation option if you want to bypass FEN validation during initialization.

The Chess class provides several methods to query the current state of the game:

• inCheck(): Returns true if the current player's king is in check.
• isCheckmate(): Returns true if the game is over via checkmate.
• isDraw(): Returns true if the game is a draw.
• isGameOver(): Returns true if the game has ended.
• isStalemate(): Returns true if the game is a stalemate.
• isThreefoldRepetition(): Returns true if the game is a draw by threefold repetition.
• isInsufficientMaterial(): Returns true if there is insufficient material to force a mate.

The moves() method returns an array of legal moves. You can filter moves by square, piece, or request verbose move objects.

Options:

• square: Filter moves starting from a specific Square.
• piece: Filter moves for a specific PieceSymbol.
• verbose: If true, returns an array of Move objects instead of SAN strings.

Use the loadPgn(pgn, options) method to load a game from a Portable Game Notation string.

Options:

• strict: If true, enforces strict PGN compliance.
• newlineChar: Specifies the character used for newlines in the PGN.

Use the load(fen, options) method to set the game state to a specific FEN string.

Options:

• skipValidation: If true, bypasses FEN validation.
• preserveHeaders: If true, preserves PGN headers (if applicable).