I would read through AirBnB's JS style guide. Very well structured, and most rules have reasons specified in the guide. It should cover all the unfamiliar parts for you. After that, the next biggest thing is tooling so it'd be picking a framework and seeing how the development process has changed with npm & webpack. Start with Vue, Angular, or React and go through their hello world examples. Not that you need to be a "framework developer", but they are probably the best spots to see how the development process has changed.

https://github.com/airbnb/javascript