board.js

function Board() {

  this.isWinner   = isWinner;
  this.placePiece = placePiece;

   var GOAL = 5, winnerIs, values = {'white': {}, 'black': {}};
 
    function placePiece(col, row, player) {
        values[player][col + '-' + row] = 1; 		
    }
 
    function isWinner(x, y, player) {
    	var dir = [[1,0],[0,1],[1,1],[1,-1]];
    	for(var d in dir) {
            if(getCount(player, x, y, dir[d][0], dir[d][1]) + getCount(player, x, y, -dir[d][0], -dir[d][1], false) + 1 >= GOAL) return true;
	}    	
       	return false;
    }
 
    function getCount(player, x, y, dx, dy) {
    	return values[player][(x + dx) + '-' + (y + dy)] ? 1 + getCount(player, x+dx, y+dy, dx, dy) : 0;
    }
}