Board State

[streamich]

How can I get the current board state? You have this variable board but it seems to be private, so is there a way to get the current board state?

[streamich]

Public API like this would be great:

board: function() {
    return board;
}

[streamich]

BTW, why are there 128 squares on the board?

var board = new Array(128);

[streamich]

Maybe it could be like this then:

board: function() {
    var pieces = [];
    for(var pos in SQUARES) {
        var square = board[SQUARES[pos]];
        if(square) {
            // pieces.push({
            //     type: square.type,
            //     color: square.color,
            //     pos: pos,
            // });

            // pieces.push([pos[0], parseInt(pos[1]), square.type, square.color]);

            // pieces.push([parseInt(pos[0], 18) - 10, parseInt(pos[1]) - 1, square.type, square.color === 'w']);

            pieces.push([pos, square]);
        }
    }
    return pieces;
}

[jhlywa]

The internal board uses 128 squares because of the 0x88 move generation algorithm. During move generation, the algorithm can easily tell which squares are off the board by checking for a non-zero return from square & 0x88. This saves cycles compared to the more obvious approach if (x < 0 || x > 7 || y < 0 || y > 7).

The FEN string (chess.fen()) contains the entire state of the board along with castling and en passant permissions, and move numbers. FEN is the standard way to import/export positions from chess utilities. You could also try using chess.get() if you like.

The internal board representation is not meant to be exported.

[streamich]

I wanted to use chess.js to parse a .fen string and then print the board on the screen, so exporting back to .fen is not an option for me.

I guess looping through chess.get() is the way to go.

Would be nice though to have a programmatic way of accessing the state of the whole board, like chess.toJson().

Also, for example, if I want to use chess.js to parse a .pgn game, I can load the .pgn file, but how do I access the header information? It seems you can only write header information?

.header()

Allows header information to be added to PGN output. Any number of key/value pairs can be passed to .header().

[AlexeiDarmin]

The internal board representation is not meant to be exported.

@jhlywa Being unable to access the board state is inconvenient when building bots. Without the functionality, I have to convert every fen position into an array before I can evaluate it, which is unnecassary when board already stores and works with the array.

It would be really awesome if this was part of the api :)

[jhlywa]

@AlexeiDarmin The internal board array is an atypical board configuration of 128 squares. Exporting this would eventually leak all of internal constants (e.g. RAYS, SHIFTS, etc...) used to transverse this array. Probably not ideal.

Would a simple 8x8 board array be more appropriate for your use case?

[AlexeiDarmin]

@jhlywa I believe an 8x8 board would be fine, anything that is easily loop-able. For example: column based comparisons are inconvenient via the fen string such as checking for double pawns since some math needs to be done to calculate the columns.

Visual example of how arrays make this easier.:
8/p6p/1p4p1/2p2p2/3pp3/8/8/8/8

[
[null, null, null, null, null, null, null, null],
[pawn, null, null, null, null, null, null, pawn],
[null, pawn, null, null, null, null, pawn, null],
[null, null, pawn, null, null, pawn, null, null],
[null, null, null, pawn, pawn, null, null, null],
[null, null, null, null, null, null, null, null],
[null, null, null, null, null, null, null, null],
[null, null, null, null, null, null, null, null]
]

[jhlywa]

@AlexeiDarmin I've added a board() method to master. It'll be officially included in the 0.11.0 release.

[streamich]

Thank you!

It might also make sense to have an option to return only the list of squares where some piece are actually present. Consider an empty board with just a rook:

r7/8/8/8/8/8/8/8

You could return:

{
    a8: 'r'
}

[abdurrahmanekr]

When will this feature be added?