"If you can do that effectively, you should probably be presenting and writing books on JavaScript."
If I hire someone as an experienced frontend dev, I want them to be able to explain how stuff works to other people - especially to non-frontend developers, and junior developers. I want them to be able to train others up. So yes, I want them to be able to present on JavaScript. If their answer to the question tells me they're good enough at explaining things that they could write a book on the subject? Fantastic! Put that in plus column.
If I hire someone as an experienced frontend dev, I want them to be able to explain how stuff works to other people - especially to non-frontend developers, and junior developers. I want them to be able to train others up. So yes, I want them to be able to present on JavaScript. If their answer to the question tells me they're good enough at explaining things that they could write a book on the subject? Fantastic! Put that in plus column.