Предупреждение: React.createElement: ожидал строку (для встроенных компонентов) или класс / функцию (для составных компонентов), но получил: объект

Question

Я новичок в React и столкнулся с какой-то проблемой и получил следующую ошибку: - Предупреждение: React.createElement: type is invalid - ожидалась строка (для встроенных компонентов) или класс / функция (для составных компоненты), но получил: объект. Ошибка: тип элемента недопустим: ожидается строка (для встроенных компонентов) или класс / функция (для составных компонентов), но получено: объект. Я проверил несколько блогов и реализовал их решения, но все равно получаю ту же ошибку.

индекс. js

  import React from 'react';
  import ReactDOM from 'react-dom';

  import App from './components/App';

  ReactDOM.hydrate(
  <App />,
    document.getElementById('mountNode'),
  );

Прил. js

import React, { useState } from 'react';
import { Route, Router,Link } from 'react-router-dom';
import { createMemoryHistory } from 'history';


import HomePage from './HomePage';
import About from './About';
export default function App()
{

 const history = createMemoryHistory();
return (


    <Router history={history}> 
      {/* A <Switch> looks through its children <Route>s and
          renders the first one that matches the current URL. */}

        <Route path="/about" component={About} />

        <Route path="/" component={HomePage} />

    </Router>

);
}

Ошибка

Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a 
class/function (for composite components) but got: object.
Error: Element type is invalid: expected a string (for built-in components) or a class/function (for 
composite components) but got: object.
    at ReactDOMServerRenderer.render (C:\LMS-APP\node_modules\react-dom\cjs\react-dom- 
   server.node.development.js:3743:17)
    at ReactDOMServerRenderer.read (C:\LMS-APP\node_modules\react-dom\cjs\react-dom- 
   server.node.development.js:3373:29)
    at Object.renderToString (C:\LMS-APP\node_modules\react-dom\cjs\react-dom- 
   server.node.development.js:3988:27)
    at C:\LMS-APP\src\server\/server.js:10:40
    at Layer.handle [as handle_request] (C:\LMS-APP\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\LMS-APP\node_modules\express\lib\router\route.js:137:13)
    at Route.dispatch (C:\LMS-APP\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (C:\LMS-APP\node_modules\express\lib\router\layer.js:95:5)
    at C:\LMS-APP\node_modules\express\lib\router\index.js:281:22
    at Function.process_params (C:\LMS-APP\node_modules\express\lib\router\index.js:335:12)

пакет. json

{
  "name": "LMS-APP",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev-server": "nodemon --exec babel-node src/server/server.js --ignore dist/",
    "dev-bundle": "webpack -w -d"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@babel/core": "^7.9.6",
    "@babel/node": "^7.8.7",
    "@babel/preset-env": "^7.9.6",
    "@babel/preset-react": "^7.9.4",
    "babel-loader": "^8.1.0",
    "express": "^4.17.1",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-router-dom": "^5.2.0",
    "webpack": "^4.43.0",
    "webpack-cli": "^3.3.11"
  },
  "devDependencies": {
    "babel-eslint": "^10.1.0",
    "eslint": "^7.0.0",
    "eslint-plugin-react": "^7.20.0",
    "eslint-plugin-react-hooks": "^4.0.2",
    "nodemon": "^2.0.4"
  }
}

Домашняя страница. js

import React from 'react-dom';
import {Link} from 'react-router-dom';

export default function HomePage()
{
    return(
        <div>
          <nav>
            <ul>
              <li>
               <Link to="/">Home</Link>
              </li>
              <li>
                <Link to="/about">About</Link>
              </li>
            </ul>
          </nav>
         </div> 
    );
}

сервер. js

import express from 'express';
import React from 'react';
import ReactDOMServer from 'react-dom/server';
import App from '../components/App';
import StaticRouter from 'react-router-dom';
const server = express();
server.use(express.static('dist'));

server.get('/', (req, res) => {
  const initialMarkup = ReactDOMServer.renderToString(<StaticRouter><App /></StaticRouter>);

  res.send(`
    <html>
      <head>
        <title>Sample React App</title>
  </head>
  <body>
    <div id="mountNode">${initialMarkup}</div>
    <script src="/main.js"></script>
  </body>
</html>
  `)
 });

 server.listen(4242, () => console.log('Server is running...'));

Около. js

import React from 'react-dom';

export default function About()
{
    return(
        <div>
            <h1>About</h1>
        </div>
    );
}