我是ReactJS的新手

我创建了一个称为页脚的子组件，并安装了Bootstrap程序包，但是页脚没有收到任何样式。

代码App.js-

import React,{ Component }from 'react';
import './App.css';
import Header from './components/header';
import Footer from './components/footer';

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

export default App;

Footer.js在组件文件夹下

import React from 'react';

const Footer = () => {

    return (
        <footer classname="page-footer font-small blue">
            <div classname="footer-copyright text-center py-3">© 2019 Copyright:
                <a href="http://www.google.co.uk/">Test.com</a>
            </div>
        </footer>
    );
};

export default Footer;

index.js-

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';
import 'bootstrap/dist/css/bootstrap.min.css';

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

// If you want your app to work offline and load faster,you can change
// unregister() to register() below. Note this comes with some pitfalls.
serviceWorker.register();

但是页脚中没有样式。

我们非常感谢您的帮助。