tic tac toe recurse center

index.js

const readline = require("readline");
const validLetters = "abc";
const validNumbers = "123";

const circle = "O";
const cross = "X";

let turn = circle;

let state = [
  ["", "", ""],
  ["", "", ""],
  ["", "", ""],
];

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

console.clear();
console.log("     TIC TAC TOE");
console.log("    _____________");

renderState(state);
console.log("Press a, b or c then 1, 2 or 3");
console.log("Player turn:", turn);

requestMove();

function switchTurn(turn) {
  return turn === circle ? cross : circle;
}

function checkRows(state) {
  let winner = "";
  for (let i = 0; i < state.length; i++) {
    const row = state[i];
    if (row[0] === row[1] && row[1] === row[2] && row[0] !== "") {
      winner = row[0];
      break;
    }
  }
  return winner;
}

function checkColumns(state) {
  let winner = "";
  // assumes all rows are the same length
  for (let i = 0; i < state[0].length; i++) {
    if (
      state[0][i] === state[1][i] &&
      state[1][i] === state[2][i] &&
      state[0][i] !== ""
    ) {
      winner = state[0][i];
    }
  }
  return winner;
}

function checkDiagonals(state) {
  let winner = "";
  if (state[0][0] === state[1][1] && state[1][1] === state[2][2]) {
    winner = state[0][0];
  }
  if (state[0][2] === state[1][1] && state[1][1] === state[2][0]) {
    winner = state[0][2];
  }
  return winner;
}

function checkWinner(state) {
  const winner =
    checkRows(state) || checkColumns(state) || checkDiagonals(state);
  return winner;
}

function requestMove() {
  rl.question("What is your move? ", function (move) {
    if (validateMove(move, state)) {
      state = updateState(state, move, turn);
      renderState(state);
      if (checkWinner(state) !== "") {
        console.log("Winner is:", checkWinner(state), "🎉");
        console.log("Game Over");
        rl.close();
      } else {
        turn = switchTurn(turn);
        console.log("Player turn:", turn);
        requestMove();
      }
    } else {
      console.log("Invalid move");
      requestMove();
    }
  });
}

function renderState(state) {
  console.log("____| 1 | 2 | 3 | ");
  for (let i = 0; i < state.length; i++) {
    const s = state[i];
    console.log(
      "|",
      validLetters[i],
      "|",
      s[0] || " ",
      "|",
      s[1] || " ",
      "|",
      s[2] || " ",
      "|",
    );
  }
  console.log("_________________");
}

function updateState(state, moveString, player) {
  const letter = moveString[0];
  const number = moveString[1];
  const row = validLetters.indexOf(letter);
  const column = validNumbers.indexOf(number);
  state[row][column] = player;
  return state;
}

function validateMove(moveString, state) {
  if (moveString.length !== 2) {
    return false;
  }
  const letter = moveString[0];
  const number = moveString[1];

  let valid = false;
  if (validLetters.indexOf(letter) > -1 && validNumbers.indexOf(number) > -1) {
    valid = true;
  }

  const row = validLetters.indexOf(letter);
  const column = validNumbers.indexOf(number);

  if (state[row][column] !== "") {
    valid = false;
  }
  return valid;
}