React路由器v4错误“未捕获ReferenceError:未定义路由器”

npm install react-router-dom
# 或者
yarn add react-router-dom

import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';

import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';
import App from './App';
import Home from './Home';
import About from './About';

ReactDOM.render(
  <Router>
    <Switch>
      <Route exact path="/" component={Home} />
      <Route path="/about" component={About} />
      {/* 其他路由 */}
    </Switch>
  </Router>,
  document.getElementById('root')
);

import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';
import App from './App';
import Home from './Home';
import About from './About';

ReactDOM.render(
  <Router>
    <Switch>
      <Route exact path="/" component={Home} />
      <Route path="/about" component={About} />
    </Switch>
  </Router>,
  document.getElementById('root')
);

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

function App() {
  return (
    <div>
      <nav>
        <ul>
          <li>
            <Link to="/">Home</Link>
          </li>
          <li>
            <Link to="/about">About</Link>
          </li>
        </ul>
      </nav>
      {/* 其他内容 */}
    </div>
  );
}

export default App;

import React from 'react';

function Home() {
  return <h2>Home</h2>;
}

export default Home;

import React from 'react';

function About() {
  return <h2>About</h2>;
}

export default About;