default.js

var game, board;

window.init = function () {    
    game = new Chess();
    board = new ChessBoard('board', cfg);

    var socket = io();
    $('#go').click(function () {
        socket.emit('button', $('#name').val());
        //socket.emit('button', "dude");
    });

    socket.on('button', function (msg) {
        $('#messages').append($('<li>').text(msg));
    });
};



// do not pick up pieces if the game is over
// only pick up pieces for the side to move
var onDragStart = function(source, piece, position, orientation) {
  if (game.game_over() === true ||
      (game.turn() === 'w' && piece.search(/^b/) !== -1) ||
      (game.turn() === 'b' && piece.search(/^w/) !== -1)) {
    return false;
  }
};

var onDrop = function(source, target) {
  // see if the move is legal
  var move = game.move({
    from: source,
    to: target,
    promotion: 'q' // NOTE: always promote to a queen for example simplicity
  });

  // illegal move
  if (move === null) return 'snapback';

};

// update the board position after the piece snap 
// for castling, en passant, pawn promotion
var onSnapEnd = function() {
  board.position(game.fen());
};

var cfg = {
  draggable: true,
  position: 'start',
  onDragStart: onDragStart,
  onDrop: onDrop,
  onSnapEnd: onSnapEnd
};