我用JavaScript做了一个Tic-tac-toe游戏，但我不知道添加代码

// 游戏状态
let board = [
  ['', '', ''],
  ['', '', ''],
  ['', '', '']
];

// 当前玩家
let currentPlayer = 'X';

// 游戏是否结束
let gameEnded = false;

// 胜利组合的数组
const winningCombinations = [
  // 横向胜利组合
  [0, 1, 2],
  [3, 4, 5],
  [6, 7, 8],
  // 纵向胜利组合
  [0, 3, 6],
  [1, 4, 7],
  [2, 5, 8],
  // 对角线胜利组合
  [0, 4, 8],
  [2, 4, 6]
];

// 点击格子时的处理函数
function cellClicked(row, col) {
  // 如果游戏已结束或当前格子已被填充，则不做任何操作
  if (gameEnded || board[row][col] !== '') {
    return;
  }

  // 更新格子状态
  board[row][col] = currentPlayer;

  // 在界面上显示当前玩家的标记
  document.getElementById(`cell-${row}-${col}`).innerText = currentPlayer;

  // 检查当前玩家是否获胜
  if (checkWin(currentPlayer)) {
    // 游戏结束，显示获胜信息
    document.getElementById('status').innerText = `Player ${currentPlayer} wins!`;
    gameEnded = true;
  } else if (checkDraw()) {
    // 检查是否平局
    document.getElementById('status').innerText = 'It\'s a draw!';
    gameEnded = true;
  } else {
    // 切换玩家
    currentPlayer = currentPlayer === 'X' ? 'O' : 'X';
    document.getElementById('status').innerText = `Player ${currentPlayer}'s turn`;
  }
}

// 检查当前玩家是否获胜
function checkWin(player) {
  for (let combination of winningCombinations) {
    let [a, b, c] = combination;
    if (board[Math.floor(a / 3)][a % 3] === player &&
        board[Math.floor(b / 3)][b % 3] === player &&
        board[Math.floor(c / 3)][c % 3] === player) {
      return true;
    }
  }
  return false;
}

// 检查是否平局
function checkDraw() {
  for (let row = 0; row < 3; row++) {
    for (let col = 0; col < 3; col++) {
      if (board[row][col] === '') {
        return false;
      }
    }
  }
  return true;
}