title: What does "export default" do in JSX?
body: <p>I want to ask what the last sentence means and does (export default HelloWorld;) but I can't find any tutorials about it.</p>
  
  <pre><code>// hello-world.jsx
  
  import React from 'react';
  
  class HelloWorld extends React.Component {
    render() {
      return &lt;p&gt;Hello, world!&lt;/p&gt;;
    }
  }
  
  export default HelloWorld;
  </code></pre>