I keep a big list of links to high-quality tutorials on React and related topics ([0]). As part of that list, I have a couple categories that point to info on learning Javascript ([1]), using the new Javascript ES6+ features and syntax ([2]), and understanding what the many modern dev tools do and how they fit together ([3]). That last category also has links to some "suggested learning approach"-type pages.

Hopefully these help!

[0] https://github.com/markerikson/react-redux-links

[1] https://github.com/markerikson/react-redux-links/blob/master...

[2] https://github.com/markerikson/react-redux-links/blob/master...

[3] https://github.com/markerikson/react-redux-links/blob/master...