The goal of Flow was apparently to be able to add types to some parts of the code while leaving the rest of it unchanged, this to me was confusing, because at t

The goal of Flow was apparently to be able to add types to some parts of the code while leaving the rest of it unchanged, this to me was confusing, because at that time, you were already able to do that with TypeScript. Over time the argument in favour of Flow became the following: it has a "sound" type system, which means it produces better results in some extreme cases where TypeScript fumbles. I didn't seem to ever hit those corner cases, I just enjoyed the fact that TypeScript had a more robust type system. Next argument was: Flow is just a linter that strips out the type annotations. Most projects that use Flow use a transpiler, which renders the linter argument moot. As of today, I don't know of anything that you can do with Flow and cannot do with TypeScript, the reverse is not true though. Unless I'm missing something, it seems that Flow's existence is based on tribalism rather than rationality, the Angular team realised that if there is already a project out there that covers 99% of their needs, it might be better to just work with the project instead of reinventing the wheel, Facebook seems to have been ignorant of that. Facebook developers seem to have a tendency to just re-invent the wheel instead of collaborating, see Yarn, I'm not saying that they are wrong in doing so, there is a chance that they might be on the right, however I don't feel that is the case when it comes to TypeScript.