Five in a row

board.js

function Board() {
    var GOAL = 5, winnerIs, values = {'white': {}, 'black': {}};

    function placePiece(col, row, player) {
        values[player][col + '-' + row] = 1;
        winnerIs = findWinner(col, row, player);
    }

    function findWinner(x, y, player) {
        for (var radian = 0; radian < Math.PI; radian += Math.PI / 4) {
            var dx = Math.round(Math.cos(radian)),
                dy = Math.round(Math.sin(radian));

            if (getCount(player, x, y, dx, dy, true) + getCount(player, x, y, dx, dy, false) + 1 >= GOAL) {
                return player;
            }
        }
    }

    function getCount(player, x, y, dx, dy, along) {
        var k = 1;
        while (values[player][(x + (k * (along ? dx : -dx))) + '-' + (y + (k * (along ? dy : -dy)))]) {
            k++;
        }

        return k - 1;
    }

    return {
        placePiece: placePiece,
        winner: function () {
            return winnerIs;
        }
    };
}