On Refactoring With Generic Types

Back in 2015, only a handful of people using JavaScript (even professionally) knew what generic types were, I believe. While both TypeScript and Flow were already around (at least since October 2014 and June 2015 respectively) and supported them (1, 2), they were still a niche and far from being popular. Nowadays, I see undergrads applying for an internship who not only know that they exist and what the syntax looks like, but can give a reasonable example of using them as well. Sure, they may...