simple-chess-step-2

by lhartikk

HTML

<script src="https://cdn.rawgit.com/lhartikk/simple-chess-ai/master/lib/js/chess.js"></script>
<script src="https://chessboardjs.com/js/chessboard.js"></script>
<!-- Used to get images -->
<base href="http://chessboardjs.com/" />
<h3 class="board">
Evaluation function
</h3>
<div id="board" class="board"></div>
<br>
<div class="info">
    <div id="move-history" class="move-history">
    </div>
</div>

CSS

.board {
    width: 400px;
    margin: auto
}

.info {
    width: 400px;
    margin: auto;
}

.move-history {
    max-height: 100px;
    overflow-y: scroll;
}

/*!
 * chessboard.js $version$
 *
 * Copyright 2013 Chris Oakman
 * Released under the MIT license
 * https://github.com/oakmac/chessboardjs/blob/master/LICENSE
 *
 * Date: $date$
 */

/* clearfix */
.clearfix-7da63 {
  clear: both;
}

/* board */
.board-b72b1 {
  border: 2px solid #404040;
  -moz-box-sizing: content-box;
  box-sizing: content-box;
}

/* square */
.square-55d63 {
  float: left;
  position: relative;

  /* disable any native browser highlighting */
  -webkit-touch-callout: none;
    -webkit-user-select: none;
     -khtml-user-select: none;
       -moz-user-select: none;
        -ms-user-select: none;
            user-select: none;
}

/* white square */
.white-1e1d7 {
  background-color: #f0d9b5;
  color: #b58863;
}

/* black square */
.black-3c85d {
  background-color: #b58863;
  color: #f0d9b5;
}

/* highlighted square */
.highlight1-32417, .highlight2-9c5d2 {
  -webkit-box-shadow: inset 0 0 3px 3px yellow;
  -moz-box-shadow: inset 0 0 3px 3px yellow;
  box-shadow: inset 0 0 3px 3px yellow;
}

/* notation */
.notation-322f9 {
  cursor: default;
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 14px;
  position: absolute;
}
.alpha-d2270 {
  bottom: 1px;
  right: 3px;
}
.numeric-fc462 {
  top: 2px;
  left: 2px;
}

JavaScript

var board,
    game = new Chess();

/*The "AI" part starts here */

var calculateBestMove =function(game) {

    var newGameMoves = game.ugly_moves();
    var bestMove = null;
    //use any negative large number
    var bestValue = -9999;

    for(var i = 0; i < newGameMoves.length; i++) {
        var newGameMove = newGameMoves[i];
        game.ugly_move(newGameMove);

        //take the negative as AI plays as black
        var boardValue = -evaluateBoard(game.board())
        game.undo();
        if(boardValue > bestValue) {
            bestValue = boardValue;
            bestMove = newGameMove
        }
    }

    return bestMove;

};

var evaluateBoard = function (board) {
    var totalEvaluation = 0;
    for (var i = 0; i < 8; i++) {
        for (var j = 0; j < 8; j++) {
            totalEvaluation = totalEvaluation + getPieceValue(board[i][j]);
        }
    }
    return totalEvaluation;
};

var getPieceValue = function (piece) {
    if (piece === null) {
        return 0;
    }
    var getAbsoluteValue = function (piece) {
        if (piece.type === 'p') {
            return 10;
        } else if (piece.type === 'r') {
            return 50;
        } else if (piece.type === 'n') {
            return 30;
        } else if (piece.type === 'b') {
            return 30 ;
        } else if (piece.type === 'q') {
            return 90;
        } else if (piece.type === 'k') {
            return 900;
        }
        throw "Unknown piece type: " + piece.type;
    };

    var absoluteValue = getAbsoluteValue(piece, piece.color === 'w');
    return piece.color === 'w' ? absoluteValue : -absoluteValue;
};

/* board visualization and games state handling starts here*/

var onDragStart = function (source, piece, position, orientation) {
    if (game.in_checkmate() === true || game.in_draw() === true ||
        piece.search(/^b/) !== -1) {
        return false;
    }
};

var makeBestMove = function () {
    var bestMove = getBestMove(game);
   ...