count number of pieces or count captures about chess.js

[jhlywa]

So I think your approach would run into problems whenever a player promotes a pawn - it would incorrectly assume the pawn was captured. A better way to build the captured pieces sidebar would be to scan the game history (chess.history({ verbose: true })) and count each captured piece, like so:

var history = chess.history({verbose: true});
var initial = {w: {p: 0, n: 0, b: 0, r: 0, q: 0},
               b: {p: 0, n: 0, b: 0, r: 0, q: 0}};

var captured = history.reduce(function(acc, move) {
  if ('captured' in move) {
    var piece = move.captured;
    // switch colors since the history stores the color of the player doing the
    // capturing, not the color of the captured piece
    var color = move.color == 'w' ? 'b' : 'w';
    acc[color][piece] += 1;
    return acc;
  } else {
    return acc;
  }
}, initial);

Does that work for you?

[tgoldenberg]

Yes, I was able to get the captured pieces to the sidebar, except for in the case of pawn promotion. I will try your suggested method as well. Also, I notice that in my two player real-time game, the castling doesn't show on the opponent's screen - instead, just the king's move - i.e., `e1-g1'. How can I pass into the board.move(notation) to make the king move as well? Or do I have to pass in FEN notation? Here is my code, using Pusher :

channel.bind('new_move', function(data) {

onDrop(data.object_notation.split('-')[0], data.object_notation.split('-')[1]);
board.move(data.object_notation);

[jhlywa]

When you call .move(string) your string needs to be valid Standard Algebraic Notation. So in this case, the SAN for kingside castling would be chess.move('O-O'). Be warned, the SAN parser in chess.js is strict, so you'll need correct capitalization and appropriate decorations (+ for check, and # for mate) or else the move will fail and return null.

An simpler approach would be to call .move(object), like chess.move({from: 'e1', to: 'g1'}). See the .move() docs for more info.

[tgoldenberg]

This sounds great. Thank you for the suggestions!