checkWinner.js

function isWinner(board , symbol){
    // check for rows .
    if(board[0] == board[1] && board[1] == board[2] && board[2]== symbol) return symbol;
    if(board[3] == board[4] && board[4] == board[5] && board[5]== symbol) return symbol;
    if(board[6] == board[7] && board[7] == board[8] && board[8]== symbol) return symbol;
    
    // check for coloumns
    if(board[0] == board[3] && board[3] == board[6] && board[6]== symbol) return symbol;
    if(board[1] == board[4] && board[4] == board[7] && board[7]== symbol) return symbol;
    if(board[2] == board[5] && board[5] == board[8] && board[8]== symbol) return symbol;
    
    // diagonal check
    if(board[0] == board[4] && board[4] == board[8] && board[4]== symbol) return symbol;
    if(board[2] == board[4] && board[4] == board[6] && board[4]== symbol) return symbol;

    //if no one win the game .
    return "";
}
export default isWinner;