class component to arrow function

routes/sample_router.js

-const express = require('express');
-const router = express.Router();
-
-router.get('/', (req, res, next) => {
-    res.send('Hello, I am sample router');
-});
-
-module.exports = router;
\ No newline at end of file

src/App.js

 import React, { Component } from 'react';
 
-class App extends Component {
-  render() {
+const App = () => {
     return (
-      <div>
-        Hello, React Boilerplate!
-      </div>
+      <h1>
+        What time is it?
+      </h1>
     );
 }
-}
 
 export default App;

src/index.js

@@ -2,6 +2,9 @@ import React from 'react';
 import ReactDOM from 'react-dom';
 import App from './App';
 
-ReactDOM.render(<App />, document.getElementById('root'));
+var container = document.getElementById('root');
+var root = ReactDOM.createRoot(container);
+
+root.render(<App />);
 
 module.hot.accept()
\ No newline at end of file