Formatting, Commenting, variable naming, debugging, testing, flow, a little on typescript.
Learn good habits. I don't mean some fad style guide. I mean learn not to expose globals, learn not to loop over stuff multiple times when once will suffice, learn when not to do something.
Learn to tune out the noise. There's lots of BS out there from people who have a lot of time to write about JavaScript, because they don't have to manage and write a lot of real code.
