Being confidently programming language agnostic
I know formal education often gets a lot of criticism around HN, but I think the approach the article is talking about is heavily mirrored in most university computer science curriculums.Universities tend to focus on paradigms and patterns, and typically force a student to learn at least 3 languages throughout their education (much more if they want to). Just in my undergrad I learned C, C++, C#, Objective C, Swift, assembler, Java, Go, Javascript, Python, and Haskell. My personal experience is that university grads are much better at adapting to new languages than someone with 4 years experience in only a single language.That's of course not to say you can't do the exact same sort of education without going to school (and probably in less time).