react.dev/_js/examples/markdown.js

var MARKDOWN_COMPONENT = `
class MarkdownEditor extends React.Component {
  constructor(props) {
    super(props);
    this.handleChange = this.handleChange.bind(this);
    this.state = {value: 'Type some *markdown* here!'};
  }

  handleChange() {
    this.setState({value: this.refs.textarea.value});
  }

  getRawMarkup() {
    var md = new Remarkable();
    return { __html: md.render(this.state.value) };
  }

  render() {
    return (
      <div className="MarkdownEditor">
        <h3>Input</h3>
        <textarea
          onChange={this.handleChange}
          ref="textarea"
          defaultValue={this.state.value} />
        <h3>Output</h3>
        <div
          className="content"
          dangerouslySetInnerHTML={this.getRawMarkup()}
        />
      </div>
    );
  }
}

ReactDOM.render(<MarkdownEditor />, mountNode);
`.trim();

ReactDOM.render(
  <ReactPlayground codeText={MARKDOWN_COMPONENT} />,
  document.getElementById('markdownExample')
);