react_example.html

gistfile1.txt

<div id="root"></div>
<script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
<script type="text/babel">
class Greeting extends React.Component {
    render() {
        return (<p>Hello world</p>);
    }
}
ReactDOM.render(
    <Greeting />,
    document.getElementById('root')
);
</script>