If you already know JavaScript, but don’t have much React experience, you’ll learn what you need get started. You’ll then be able to develop your own blocks and extend Gutenberg.

You’ll see the most important parts of ES6 and JSX to know. Also, you’ll learn the basics of how React works, see a basic build setup, and learn about ES6 modules.

https://2019.brisbane.wordcamp.org/session/a-quickstart-guide-to-react-development/