It seems to me that SQL, C++, and Excel VBA (in that order) are probably the 3 top evergreen skills that folks in the 80s or 90s are still able to utilize in a career spanning 20+ years! JavaScript is probably the equivalent for this generation.
Have fun trying to integrate the "document.write('hello world')" example you found from stackoverflow into a react app while being a beginner and not really knowing why exactly they aren't compatible.