Start Point for react.

index.js

import { render } from '@wordpress/element'
import domReady from '@wordpress/dom-ready';

const App = () => {
    return <>Welcome to WP react Tuts</>
}

domReady(function () {
    if ('undefined' !== typeof document.getElementById('wp-react-plugin-test-app') && null !== document.getElementById('wp-react-plugin-test-app')) {
        render(<App />, document.getElementById('wp-react-plugin-test-app'));
    }
});