code: function TicTacToeBoard(cells){
      this.board = [];
  		for(var i=0; i<NUM_CELLS; i++) {
        if(cells){
          this.board[i] = cells[i];
        } else {
          this.board[i] = Cell.EMPTY;
        }
  		}
    }
docs: ***************** TicTacToeBoard ********************************