ReactDOM.render is no longer supported in React 18. Use createRoot instead

index.js

import ReactDOM from 'react-dom'
import App from './App'
import './index.css'

ReactDOM.render(<App/>, document.querySelector("#root"))

>Solution :

In React 18, the Index.js file structure changed and should look like this:

import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
    <App />
);

reportWebVitals();