未定义React组件no-undef

Question

作为一个初学者，我正在尝试将默认的响应登陆页面从header.js渲染为index.js。 请帮我解释我哪里错了 Index.js-

import React from 'react';
import ReactDOM from 'react-dom';
import './header.css';
import Header from './header';
import registerServiceWorker from './registerServiceWorker';

class App extends Component {
    render() {
      return (
        <Header />
      );
    }
  }

ReactDOM.render(<App />, document.getElementById('root'));
registerServiceWorker();

header.js-

import React from 'react';
import ReactDOM from 'react-dom';
import './header.css';
import registerServiceWorker from './registerServiceWorker';

class Header extends Component {
    render() {
      return (
        <div className="App">
          <header className="App-header">
            <h1 className="App-title">Welcome to React</h1>
          </header>
          <p className="App-intro">
            To get started, edit <code>src/App.js</code> and save to reload.
          </p>
        </div>
      );
    }
  }

错误-

./src/index.js
  Line 7:  'Component' is not defined  no-undef