Hello,
I begin with javascript and I made this code to play TIC-TAC-TOE.
To play it you must enter a digit corresponding to the location of where you want to play (like a cellphone 1 for left top, 2 for middle top, 3 for right top and so on).
It works but i got a problem finding why sometimes I’m able to replay at a position / location that I already used, despite that I have an array and a loop that prevent this. What’s the problem ?
Thanks for helping me out 
// Tic-Tac-Toe
class Player // player
{
constructor(name) // construction of player requires only a name
{
this.name = name;
}
}
const Display = array => // Display the grid by using the array parameter values and text mecanics
{
console.log(`\n ${array[0]} | ${array[1]} | ${array[2]}\n ---------\n ${array[3]} | ${array[4]} | ${array[5]}\n ---------\n ${array[6]} | ${array[7]} | ${array[8]}\n \n`);
}
const InitTicTacToe = tictactoeArray => // Initialize the array to make an empty grid
{
for(let i = 0; i < 9; i++)
{
tictactoeArray[i]=" ";
}
}
const WinTicTacToe = (tictactoeArray, lastPlayer) => // Return 1 if a winning condition is true
{
if((((tictactoeArray[0] === tictactoeArray[1]) && (tictactoeArray[1] === tictactoeArray[2])) && ((tictactoeArray[0] === "X") || (tictactoeArray[0] === "O"))) // Top horizontal
|| (((tictactoeArray[3] === tictactoeArray[4]) && (tictactoeArray[4] === tictactoeArray[5])) && ((tictactoeArray[3] === "X") || (tictactoeArray[3] === "O"))) // Middle horizontal
|| (((tictactoeArray[6] === tictactoeArray[7]) && (tictactoeArray[7] === tictactoeArray[8])) && ((tictactoeArray[6] === "X") || (tictactoeArray[6] === "O"))) // Bottom horizontal
|| (((tictactoeArray[0] === tictactoeArray[3]) && (tictactoeArray[3] === tictactoeArray[6])) && ((tictactoeArray[0] === "X") || (tictactoeArray[0] === "O"))) // Left vertical
|| (((tictactoeArray[1] === tictactoeArray[4]) && (tictactoeArray[4] === tictactoeArray[7])) && ((tictactoeArray[1] === "X") || (tictactoeArray[1] === "O"))) // Middle vertical
|| (((tictactoeArray[2] === tictactoeArray[5]) && (tictactoeArray[5] === tictactoeArray[8])) && ((tictactoeArray[2] === "X") || (tictactoeArray[2] === "O"))) // Right vertical
|| (((tictactoeArray[0] === tictactoeArray[4]) && (tictactoeArray[4] === tictactoeArray[8])) && ((tictactoeArray[0] === "X") || (tictactoeArray[0] === "O"))) // Left top bottom right diagonal
|| (((tictactoeArray[2] === tictactoeArray[4]) && (tictactoeArray[4] === tictactoeArray[6])) && ((tictactoeArray[2] === "X") || (tictactoeArray[2] === "O"))))
{
console.log(`${lastPlayer.name} won !`); // Display the victory
return 1; // return 1
}
}
const GameTicTacToe = (tictactoeArray, player1, player2) => // Play the game itself
{
InitTicTacToe(tictactoeArray); // Initialize the array
let usedLocation = []; // Array of locations already used
let i = 0; // while loop variable
let winner = "no"; // winner detection
while((i < tictactoeArray.length) && (winner != "yes")) // 9 turns or less if there is a winner
{
let lastPlayer = ""; // Last player
let location = ""; // Location where you want to put your mark
if((i%2) === 0) // Player 1 turn
{
location = Number(prompt(`${player1.name}, choose your X`)); // Location where you want to put your mark
for(let i = 0; i< usedLocation.length; i++) // Look in the array of locations already used
{
while((location === usedLocation[i]) || ((location !== 1) && (location !== 2) && (location !== 3) && (location !== 4)
&& (location !== 5) && (location !== 6) && (location !== 7) && (location !== 8) && (location !== 9))) // Any used location or wrong location
{
alert("Please make a valid location choice");
location = Number(prompt(`${player1.name}, choose your X`)); // Re-enter a valid choice
}
}
tictactoeArray[location-1]="X"; // Update the grid with the mark
lastPlayer = player1; // Update the last player
}
else // Player 2 turn
{
location = Number(prompt(`${player2.name}, choose your O`)); // Location where you want to put your mark
for(let i = 0; i< usedLocation.length; i++) // Look in the array of locations already used
{
while((location === usedLocation[i]) || ((location !== 1) && (location !== 2) && (location !== 3) && (location !== 4)
&& (location !== 5) && (location !== 6) && (location !== 7) && (location !== 8) && (location !== 9))) // Any used location or wrong location
{
alert("Please make a valid location choice");
location = Number(prompt(`${player2.name}, choose your O`)); // Re-enter a valid choice
}
}
tictactoeArray[location-1]="O"; // Update the grid with the mark
lastPlayer = player2; // Update the last playe
}
usedLocation.push(location); // Update the array with the previous used location
for(let i = 0; i < usedLocation.length; i++)
{
console.log(`${usedLocation[i]} `); ///////////////////////////
}
console.log(`Round ${i+1} :\n`); // Display the round no at the end of the round
Display(tictactoeArray); // Display the grid at the end of the round
if(WinTicTacToe(tictactoeArray, lastPlayer) === 1) // Check if someone just won, function return 1
{
winner = "yes"; // winner string changed to yes if someone won
};
i++; // while incrementation
}
}
const player1 = new Player(prompt("Choose player 1 name :")); // Create player 1
const player2 = new Player(prompt("Choose player 2 name :")); // Create player 2
alert("TIC-TAC-TOE !"); // Beginning message
let choice = ""; // choice
choice = Number(prompt("Make your choice :\n 1 : Play \n 2 : Change Name\n 0 : Quit")); // Turn the choice into a number
while(choice !== 0) // While user don't choose to leave
{
switch(choice) // switch the choice
{
case 1:
const tictactoeArray = [];
GameTicTacToe(tictactoeArray, player1, player2); // Play the game
break;
case 2:
player1.name = prompt("Choose player 1 name :"); // Change player 1 name
player2.name = prompt("Choose player 2 name :"); // Change player 2 name
break;
}
choice = Number(prompt("Make your choice :\n 1 : Play \n 2 : Change Name\n 0 : Quit")); // Turn the choice into a number
}
alert("Goodbye !"); // End message