Thanks for the feedback.
The in-code documentation is great. I mention it indirectly, i.e. Intellisense. I might update the article to mention that point more explicitly.
Switching build chains is not really pertinent to this article as the premise is to use TypeScript. I understand though that the Babel ecosystem is what most are used to, so transitioning to the TS build chain could be a pain to some.
Thanks for your answer. About the in-code documentation: even if you don't use Intellisense, it helps: you can get an idea about how to use a library much faster with type annotations.
As about the transitioning Even if the legacy project doesn't use babel, but plain ES5, maybe with jQuery, you can still add some type comments like /* : string */ (or even let flow's type inference do its magic; it will usually cover ~50% of your project without you doing anything) and enjoy at least a bit of type safety without changing anything else.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.