Interactive tic-tac-toe in a terminal

tictactoe.js

const clearScreen = () => {
  process.stdout.cursorTo(0, 0);
  process.stdout.clearScreenDown();
};

clearScreen();
console.log('Welcome to TicTacToe!');
console.log('Please select your opponent:');
console.log('  1. Human');
console.log('  2. Computer');

process.stdin.setRawMode(true);
process.stdin.setEncoding('utf8');
process.stdin.on('data', function (key) {
  if (key === '1' || key === '2') {
    opponent = key === '1' ? 'human' : 'computer';

    process.stdin.removeAllListeners('data');
    
    process.stdin.on('data', function (key) {
      switch (key) {
        case '\u001B\u005B\u0041': // Arrow up
          moveCursor('up');
          break;
        case '\u001B\u005B\u0042': // Arrow down
          moveCursor('down');
          break;
        case '\u001B\u005B\u0043': // Arrow right
          moveCursor('right');
          break;
        case '\u001B\u005B\u0044': // Arrow left
          moveCursor('left');
          break;
        case '\u000D': // Carrige Return
          if (squareIsEmpty()) {
            updateBoardState();
            checkForWinner();
            switchPlayer();
            renderBoard();
          } else {
            renderBoard('That square is already taken. Try again.');
          }
          break;
        case '\u0003': // Ctrl + C
          clearScreen();
          process.exit();
          break;
        default:
          break;
      }
    });

    renderBoard();
  }
});

let opponent = undefined;
let winner = undefined;
let currentPlayer = {
  name: 'Player 1',
  mark: 'X',
};
const cursorBoardPosition = {
  row: 0,
  column: 0,
};
const boardState = [
  [' ', ' ', ' '],
  [' ', ' ', ' '],
  [' ', ' ', ' '],
];

const renderBoard = (message) => {
  clearScreen();
  console.log(boardState[0].join('|'));
  console.log(`—————`);
  console.log(boardState[1].join('|'));
  console.log(`—————`);
  console.log(boardState[2].join('|'));

  if (!winner) {
    console.log(`\n${message ? `${message}\n` : ''}${currentPlayer.name}'s turn.`);
    console.log('\nUse the arrow keys to move the cursor and press enter to place your mark.');
    process.stdout.cursorTo(cursorBoardPosition.column * 2, cursorBoardPosition.row * 2);
  } else {
    if (winner === 'tie') {
      console.log(`\nIt's a tie!`);
    } else {
      console.log(`\n${winner} wins!`);
    }
    process.exit();
  }
};

const moveCursor = (direction) => {
  switch (direction) {
    case 'up':
      if (cursorBoardPosition.row > 0) {
        cursorBoardPosition.row -= 1;
        process.stdout.moveCursor(0, -2);
      }
      break;
    case 'right':
      if (cursorBoardPosition.column < 2) {
        cursorBoardPosition.column += 1;
        process.stdout.moveCursor(2, 0);
      }
      break;
    case 'down':
      if (cursorBoardPosition.row < 2) {
        cursorBoardPosition.row += 1;
        process.stdout.moveCursor(0, 2);
      }
      break;
    case 'left':
      if (cursorBoardPosition.column > 0) {
        cursorBoardPosition.column -= 1;
        process.stdout.moveCursor(-2, 0);
      }
      break;
  }
};

const updateBoardState = () => {
  boardState[cursorBoardPosition.row][cursorBoardPosition.column] = currentPlayer.mark;
};

const squareIsEmpty = () => {
  return boardState[cursorBoardPosition.row][cursorBoardPosition.column] === ' ';
};

const checkForWinner = () => {
  const mark = currentPlayer.mark;

  const rowsWin = () => {
    return boardState[0].every((square) => square === mark) || boardState[1].every((square) => square === mark) || boardState[2].every((square) => square === mark);
  };
  const columnsWin = () => {
    return (
      (boardState[0][0] === mark && boardState[1][0] === mark && boardState[2][0] === mark) ||
      (boardState[0][1] === mark && boardState[1][1] === mark && boardState[2][1] === mark) ||
      (boardState[0][2] === mark && boardState[1][2] === mark && boardState[2][2] === mark)
    );
  };
  const diagonalsWin = () => {
    return (boardState[0][0] === mark && boardState[1][1] === mark && boardState[2][2] === mark) || (boardState[0][2] === mark && boardState[1][1] === mark && boardState[2][0] === mark);
  };

  if (rowsWin() || columnsWin() || diagonalsWin()) {
    winner = currentPlayer.name;
  } else if (boardState.every((row) => row.every((square) => square !== ' '))) { // Check for tie
    winner = 'tie';
  }
};

const switchPlayer = () => {
  if (currentPlayer.name === 'Player 1') {
    if (opponent === 'human') {
      currentPlayer = { name: 'Player 2', mark: 'O' };
    } else if (opponent === 'computer') {
      currentPlayer = { name: 'TicBot', mark: 'O' };
      
      // Bot player will make a move with a small delay to make it seem like it's thinking
      setTimeout(() => {
        while (squareIsEmpty() === false) {
          cursorBoardPosition.row = Math.floor(Math.random() * 3);
          cursorBoardPosition.column = Math.floor(Math.random() * 3);
        }
        updateBoardState();
        checkForWinner();
        switchPlayer();
        renderBoard();
      }, 300)
    }
  } else {
    currentPlayer = { name: 'Player 1', mark: 'X' };
  }
};