> I tried Flow and TypeScript for the first time a few months ago. Flow is absolutely abandoned and dying. TypeScript is taking over where Flow left off, and is far ahead of the game by now. I use TypeScript with create-react-app in my client work and it is invaluable and a wonderful experience, with no downsides as far as I can see.
To add to that, the only reason I can see to use Flow in 2018 instead of TypeScript is if you already have a large project that uses Flow and migrating to TypeScript might take a few days. But even then it's probably worth making the switch. I have noticed a much smoother experience and much better integration with TypeScript than with Flow. And there are many type errors that Flow never caught no matter how much I tried to configure it right. Existing code bases may have these too. Even more reason to switch sooner than later!
We are in the process of doing this on a moderately large product. We've found TypeScript itself has much less friction to write (quicker development), and has a lot less gotchas (probably because it restricts the language itself, unlike Flow), so porting the code has been a big task but a very positive one. We went with Flow originally because it would work with our untyped JS better, but in hindsight we should have bitten the bullet earlier and gone straight to TS.
We're still exporting Flow types generated from TS modules to be imported by older projects (which is... _okay_). I would recommend just choosing the better option from the outset. You'll save hours researching why Flow has a problem (and eventually just writing `// $FlowFixMe <https://github.com/some-flow-issue/666` and moving on). I don't see any compelling reason to start a Flow project these days.
> I tried Flow and TypeScript for the first time a few months ago. Flow is absolutely abandoned and dying. TypeScript is taking over where Flow left off, and is far ahead of the game by now. I use TypeScript with create-react-app in my client work and it is invaluable and a wonderful experience, with no downsides as far as I can see.
To add to that, the only reason I can see to use Flow in 2018 instead of TypeScript is if you already have a large project that uses Flow and migrating to TypeScript might take a few days. But even then it's probably worth making the switch. I have noticed a much smoother experience and much better integration with TypeScript than with Flow. And there are many type errors that Flow never caught no matter how much I tried to configure it right. Existing code bases may have these too. Even more reason to switch sooner than later!