[vanwalj]

Having experience with both on Node back-end projects, I can tell you than IMHO Flow is smarter, especially on union types, BUT there are way more TS community type definitions available right now.

[johnfn]

I'd be curious in which ways flow is more intelligent than TS.

[vanwalj]

Here are some examples: TS: https://www.typescriptlang.org/play/#src=type%20TA%20%3D%20%... Flow: https://flow.org/try/#0PQKgBAAgZgNg9gdzCYAoVAXAngBwKZgCSAgmA...

With Typescript, you have to write custom Type Guards functions, whereas Flow is smart enough to infer type

[johnfn]

If you use discriminated union types - e.g. give them both a type key which is a unique string, then you don't need type guards as typescript is smart enough to understand that checking the type key does the type discrimination.

[vanwalj]

Sure, but you don't always have control over an external module or service, and it still something flow is better at

[johnfn]

Yeah, that's true. I don't know why you've been downvoted. You have a legitimate answer.

[boubiyeah]

Me too. I don't really see how you can get any smarter with union types than with TS 2.2+