React Boilerplate – Quickly test React component code in CodePen – https://codepen.io/schafeld/pen/BaXOLXj?editors=1111

index.html

<div id="app"></div>


<!--
In JS window use dependencies:
https://unpkg.com/react@18/umd/react.development.js
https://unpkg.com/react-dom@18/umd/react-dom.development.js

Use Babel precompiler.
-->

react-dummy-tester.markdown

React Dummy Tester

A Pen by Oliver Schafeld on CodePen.

License.

script.babel

/*
function App() {
   const handler = () => console.log('fourth example')
   return ( 
      <div> 
        <button onClick = {handler} >
          Click Me!
        </button>
      </div>
   )
}
export default App
*/

const handler = () => console.log('fourth example')

class App extends React.Component {
  
  render() {
   return ( 
      <div> 
        <button onClick = {handler} >
          Click Me!
        </button>
      </div>
   )
  }
}

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

scripts

<script src="https://unpkg.com/react@18/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script>

This is a gist for quickly testing a piece of React component code in CodePen.