• https://javascriptforwp.com/product/learn-deeply-course/
• https://es6.io/
• https://reactforbeginners.com/
• https://gutenberg.courses/development/
• https://wpscholar.com/blog/should-i-learn-react-to-build-gutenberg-blocks/
• https://vip.wordpress.com/2018/06/13/jumpstart-gutenberg-testing-transition-ramp/

To learn more, see our resource list for JavaScript for WordPress developers