chess.js
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chess.js is a Javascript chess library that is used for chess move
generation/validation, piece placement/movement, and check/checkmate/stalemate
detection - basically everything but the AI.
chess.js has been extensively tested in node.js and most modern browsers.
Installation
To install the stable version:
npm install --save chess.js
chess.js is also available via CDNJS:
<script src="https://cdnjs.cloudflare.com/ajax/libs/chess.js/0.10.1/chess.js"></script>
Example Code
The code below plays a complete game of chess ... randomly.
var Chess = require('./chess').Chess;
var chess = new Chess();
while (!chess.game_over()) {
var moves = chess.moves();
var move = moves[Math.floor(Math.random() * moves.length)];
chess.move(move);
}
console.log(chess.pgn());
Sites Using chess.js
Need a user interface? Try Chris Oakman's excellent
chessboard.js library. See
chessboard.js - Random vs Random for
an example integration of chess.js with chessboard.js.
API
Constructor: Chess([ fen ])
The Chess() constructor takes a optional parameter which specifies the board configuration
in Forsyth-Edwards Notation.
var chess = new Chess();
var chess = new Chess('r1k4r/p2nb1p1/2b4p/1p1n1p2/2PP4/3Q1NB1/1P3PPP/R5K1 b - c3 0 19');
.ascii()
Returns a string containing an ASCII diagram of the current position.
var chess = new Chess();
chess.move('e4');
chess.move('e5');
chess.move('f4');
chess.ascii();
.clear()
Clears the board.
chess.clear();
chess.fen();
.fen()
Returns the FEN string for the current position.
var chess = new Chess();
chess.move('e4');
chess.move('e5');
chess.move('f4');
chess.fen();
.game_over()
Returns true if the game has ended via checkmate, stalemate, draw, threefold repetition, or insufficient material. Otherwise, returns false.
var chess = new Chess();
chess.game_over();
chess.load('4k3/4P3/4K3/8/8/8/8/8 b - - 0 78');
chess.game_over();
chess.load('rnb1kbnr/pppp1ppp/8/4p3/5PPq/8/PPPPP2P/RNBQKBNR w KQkq - 1 3');
chess.game_over();
.get(square)
Returns the piece on the square:
chess.clear();
chess.put({ type: chess.PAWN, color: chess.BLACK }, 'a5')
chess.get('a5');
chess.get('a6');
.history([ options ])
Returns a list containing the moves of the current game. Options is an optional
parameter which may contain a 'verbose' flag. See .moves() for a description of the
verbose move fields.
var chess = new Chess();
chess.move('e4');
chess.move('e5');
chess.move('f4');
chess.move('exf4');
chess.history();
chess.history({ verbose: true });
.in_check()
Returns true or false if the side to move is in check.
var chess = new Chess('rnb1kbnr/pppp1ppp/8/4p3/5PPq/8/PPPPP2P/RNBQKBNR w KQkq - 1 3');
chess.in_check();
.in_checkmate()
Returns true or false if the side to move has been checkmated.
var chess = new Chess('rnb1kbnr/pppp1ppp/8/4p3/5PPq/8/PPPPP2P/RNBQKBNR w KQkq - 1 3');
chess.in_checkmate();
.in_draw()
Returns true or false if the game is drawn (50-move rule or insufficient material).
var chess = new Chess('4k3/4P3/4K3/8/8/8/8/8 b - - 0 78');
chess.in_draw();
.in_stalemate()
Returns true or false if the side to move has been stalemated.
var chess = new Chess('4k3/4P3/4K3/8/8/8/8/8 b - - 0 78');
chess.in_stalemate();
.in_threefold_repetition()
Returns true or false if the current board position has occurred three or more
times.
var chess = new Chess('rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1');
chess.in_threefold_repetition();
chess.move('Nf3'); chess.move('Nf6'); chess.move('Ng1'); chess.move('Ng8');
chess.in_threefold_repetition();
chess.move('Nf3'); chess.move('Nf6'); chess.move('Ng1'); chess.move('Ng8');
chess.in_threefold_repetition();
Allows header information to be added to PGN output. Any number of key/value
pairs can be passed to .header().
chess.header('White', 'Robert James Fischer');
chess.header('Black', 'Mikhail Tal');
chess.header('White', 'Morphy', 'Black', 'Anderssen', 'Date', '1858-??-??');
Calling .header() without any arguments returns the header information as an object.
chess.header();
.insufficient_material()
Returns true if the game is drawn due to insufficient material (K vs. K,
K vs. KB, or K vs. KN); otherwise false.
var chess = new Chess('k7/8/n7/8/8/8/8/7K b - - 0 1');
chess.insufficient_material()
.load(fen)
The board is cleared and the FEN string is loaded. Returns true if position was
successfully loaded, otherwise false.
var chess = new Chess();
chess.load('4r3/8/2p2PPk/1p6/pP2p1R1/P1B5/2P2K2/3r4 w - - 1 45');
chess.load('4r3/8/X12XPk/1p6/pP2p1R1/P1B5/2P2K2/3r4 w - - 1 45');
.load_pgn(pgn, [ options ])
Load the moves of a game stored in
Portable Game Notation.
Options is a optional parameter that may contain a newline_char
which is a
string representation of a RegExp (and should not be pre-escaped) and defaults
to \r?\n
). Options may also contain the sloppy
flag to handle overly
disambiguated moves (see .move
documentation for more information). Returns
true if the PGN was parsed successfully, otherwise false.
var chess = new Chess();
pgn = ['[Event "Casual Game"]',
'[Site "Berlin GER"]',
'[Date "1852.??.??"]',
'[EventDate "?"]',
'[Round "?"]',
'[Result "1-0"]',
'[White "Adolf Anderssen"]',
'[Black "Jean Dufresne"]',
'[ECO "C52"]',
'[WhiteElo "?"]',
'[BlackElo "?"]',
'[PlyCount "47"]',
'',
'1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4 Bxb4 5.c3 Ba5 6.d4 exd4 7.O-O',
'd3 8.Qb3 Qf6 9.e5 Qg6 10.Re1 Nge7 11.Ba3 b5 12.Qxb5 Rb8 13.Qa4',
'Bb6 14.Nbd2 Bb7 15.Ne4 Qf5 16.Bxd3 Qh5 17.Nf6+ gxf6 18.exf6',
'Rg8 19.Rad1 Qxf3 20.Rxe7+ Nxe7 21.Qxd7+ Kxd7 22.Bf5+ Ke8',
'23.Bd7+ Kf8 24.Bxe7# 1-0'];
chess.load_pgn(pgn.join('\n'));
chess.fen()
chess.ascii()
.move(move, [ options ])
Attempts to make a move on the board, returning a move object if the move was
legal, otherwise null. The .move function can be called two ways, by passing
a string in Standard Algebraic Notation (SAN):
var chess = new Chess();
chess.move('e4')
chess.move('nf6')
chess.move('Nf6')
Or by passing .move() a move object (only the 'to', 'from', and when necessary
'promotion', fields are needed):
var chess = new Chess();
chess.move({ from: 'g2', to: 'g3' });
Some chess applications (e.g. Fritz and Chessbase) overly disambiguate SAN. To
handle these situations, a sloppy flag can be passed to .move to allow slightly
relaxed parsing:
var chess = new Chess('r2qkbnr/ppp2ppp/2n5/1B2pQ2/4P3/8/PPP2PPP/RNB1K2R b KQkq - 3 7');
chess.move('Nge7');
chess.move('Nge7', {sloppy: true});
.moves([ options ])
Returns a list of legals moves from the current position. The function takes an optional parameter which controls the single-square move generation and verbosity.
var chess = new Chess();
chess.moves();
chess.moves({square: 'e2'});
chess.moves({square: 'e9'});
chess.moves({ verbose: true });
The piece, captured, and promotion fields contain the lowercase
representation of the applicable piece.
The flags field in verbose mode may contain one or more of the following values:
- 'n' - a non-capture
- 'b' - a pawn push of two squares
- 'e' - an en passant capture
- 'c' - a standard capture
- 'p' - a promotion
- 'k' - kingside castling
- 'q' - queenside castling
A flag of 'pc' would mean that a pawn captured a piece on the 8th rank and promoted.
.pgn([ options ])
Returns the game in PGN format. Options is an optional parameter which may include
max width and/or a newline character settings.
var chess = new Chess();
chess.header('White', 'Plunky', 'Black', 'Plinkie');
chess.move('e4');
chess.move('e5');
chess.move('Nc3');
chess.move('Nc6');
chess.pgn({ max_width: 5, newline_char: '<br />' });
.put(piece, square)
Place a piece on square where piece is an object with the form
{ type: ..., color: ... }. Returns true if piece was successfully placed,
otherwise the board remains unchanged and false is returned. put()
will fail
when passed an invalid piece or square, or when two or more kings of the
same color are placed.
chess.clear();
chess.put({ type: chess.PAWN, color: chess.BLACK }, 'a5')
chess.put({ type: 'k', color: 'w' }, 'h1')
chess.fen();
chess.put({ type: 'z', color: 'w' }, 'a1')
chess.clear();
chess.put({ type: 'k', color: 'w' }, 'a1')
chess.put({ type: 'k', color: 'w' }, 'h1')
.remove(square)
Remove and return the piece on square.
chess.clear();
chess.put({ type: chess.PAWN, color: chess.BLACK }, 'a5')
chess.put({ type: chess.KING, color: chess.WHITE }, 'h1')
chess.remove('a5');
chess.remove('h1');
chess.remove('e1');
.reset()
Reset the board to the initial starting position.
.square_color(square)
Returns the color of the square ('light' or 'dark').
var chess = Chess();
chess.square_color('h1')
chess.square_color('a7')
chess.square_color('bogus square')
.turn()
Returns the current side to move.
chess.load('rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1')
chess.turn()
.undo()
Takeback the last half-move, returning a move object if successful, otherwise null.
var chess = new Chess();
chess.fen();
chess.move('e4');
chess.fen();
chess.undo();
chess.fen();
chess.undo();
.validate_fen(fen):
Returns a validation object specifying validity or the errors found within the
FEN string.
chess.validate_fen('2n1r3/p1k2pp1/B1p3b1/P7/5bP1/2N1B3/1P2KP2/2R5 b - - 4 25');
chess.validate_fen('4r3/8/X12XPk/1p6/pP2p1R1/P1B5/2P2K2/3r4 w - - 1 45');
MUSIC
Musical support provided by:
BUGS
- The en passant square and castling flags aren't adjusted when using the put/remove functions (workaround: use .load() instead)
TODO
- Investigate the use of piece lists (this may shave a few cycles off
generate_moves() and attacked()).
- Refactor API to use camelCase - yuck.
- Add more robust FEN validation.