script.js

let gameActive = true;
let currentPlayer = "X";
let gameState = ["","","","","","","","",""];
const winningConditions = [
	[0,1,2],
	[3,4,5],
	[6,7,8],
	[0,3,6],
	[1,4,7],
	[2,5,8],
	[0,4,8],
	[2,4,6],
];
const statusDisplay = document.getElementById('status');

const winningMessage = function(){
	return currentPlayer + "'s Wins!";
}
const drawMessage = function (){
	return "Draw!";
}
const currentPlayerTurn = function(){
	return "it's" + currentPlayer + "'s turn";
}

document.querySelectorAll('.cell').forEach(function(cell){
	cell.addEventListener('click', CellClick);
});
document.querySelector('.restart').addEventListener('click', RestartGame);

function CellClick(clickedCellEvent){
	const clickedCell = clickedCellEvent.target;
	const clickedCellIndex = parseInt(clickedCell.getAttribute('data-cell-index'));
	if(gameState[clickedCellIndex] !== "" || !gameActive){
		return;
	}
	CellPlayed(clickedCell, clickedCellIndex);
	ResultValidation();
}

function CellPlayed(clickedCell, clickedCellIndex){
	gameState[clickedCellIndex] = currentPlayer;
	clickedCell.innerHTML = currentPlayer;	
}

statusDisplay.innerHTML = currentPlayerTurn();

function PlayerChange(){
	if(currentPlayer === "X"){
		currentPlayer = "O";
	}else{
		currentPlayer = "X";
	}
	statusDisplay.innerHTML = currentPlayerTurn();
}

function ResultValidation(){
	let roundWon = false;
	for(let i=0; i<=7; i++){
		const winCondition = winningConditions[i];
		let a = gameState[winCondition[0]];
		let b = gameState[winCondition[1]];
		let c = gameState[winCondition[2]];		
		if(a === '' || b === '' || c === ''){
			continue;
		}
		if(a === b && b === c){
			roundWon = true;
			break;
		}
	}
	if(roundWon){
		statusDisplay.innerHTML = winningMessage();
		gameActive = false;
		return;
	}
	let roundDraw = !gameState.includes("");
	if(roundDraw){
		statusDisplay.innerHTML = drawMessage();
		gameActive = false;
		return;
	}
	PlayerChange();
}

function RestartGame(){
	let gameActive = true;
	let currentPlayer = "X"
	let gameState = ["","","","","","","","",""];
	statusDisplay.innerHTML = currentPlayerTurn();
	document.querySelectorAll('.cell').forEach(function(cell){
		cell.innerHTML ='';
	})
}