Pick your starting point in react.js code example

Example 1: react quick tutorial

ReactDOM.render(  
    <Hello />,   
    document.getElementById("root")  
);

Example 2: create tic tac toe game in react using jsx files

useEffect(()=>{
        //checking winner row and col
        for (let i = 0; i <= 2; i++){
            const idx = (i % 3) * 3 // -> 0,3,6
            //check row
            if ( (table[idx] + table[idx+1] + table[idx+2] )=== 9 || (table[idx] + table[idx+1] + table[idx+2] ) === 15){
                setWinner([idx,idx+1,idx+2])
                gameOver()
            }
            //check col
            if ((table[i] + table[i+3] + table[i+6] )=== 9 || (table[i] + table[i+3] + table[i+6] ) === 15){
                setWinner([i,i+3,i+6])
                gameOver()
            }
        }
        //checking winner diagonal
        if ((table[0] + table[4] + table[8] ) === 15 || (table[0] + table[4] + table[8] ) === 9 ){
            setWinner([0, 4, 8])
            gameOver()
        }
        if ((table[2] + table[4] + table[6] ) === 9 || (table[2] + table[4] + table[6] ) ===15){
            setWinner([2, 4, 6])
            gameOver()
        }
        // check if table completed
        if (table.indexOf(0) === -1){
            gameOver()
        }
    }, [table])