On: Yarn – A new package manager for JavaScript

[bcherny]

> Do you think Flow was built in 3 months as a reaction to Typescript?

They probably knew that TS was in progress when they started, but I don't have a window into that. I did ask some Flow devs a few weeks ago if they are interested in merging with TS, and they answered with a categorical no.

[mambodog → bcherny]

I can't speak for either project, but personally I would say that I don't think static typing in JS is a solved problem, and at this stage to me it seems a monoculture would be much less fruitful than a competition of ideas.

[bcherny → mambodog]

I would agree if they were at all different, but they seem to be syntactically and functionally identical.

As a caveat, I am a daily TS user, and have only played around with Flow.

[pluma → bcherny]

I am not a computer scientist, but I have heard people repeatedly argue that Flow sets out to create a "sound type system" which TS intentionally does not.

What this means in practice I don't fully understand but it seems to result in enough architectural differences that it apparently makes sense to have both despite the superficial similarities in syntax and behaviour.

[mlsarecmg → bcherny]

I think the issue is that TS is non-modular and dictates javascripts reach. It behaves like no other tool and blocks others from working. Take something like React/Redux for instance, which are built around modern day javascript, but if you transpile any example on the official Redux page right now you will see TS bail out because it can't understand some of the syntax.

Flow on the other hand solves one problem and solves it well. It behaves as any other tool would.

[bcherny → mlsarecmg]

Not sure I understand. Can you give a concrete example?

[mlsarecmg → bcherny]

You can only do as much as TS allows you to, unless you route through babel in a second pass. TS is a tool that controls to which extend you can use language features that are drafted. They do pick drafts here and there, but others they omitt, object spread for instance which is very common for Redux.

As i said, try to transpile this in TS: http://redux.js.org/docs/basics/ExampleTodoList.html

This is why they made Flow.

[bcherny → mlsarecmg]

Still not sure I understand. All the code in that link is valid TS - TS is just a superset of JS.

Object spread is not part of the ES7 spec. It is a proposal which has not made it to stage 3 yet, and might still be dropped. That said, there is a TS issue tracking adding support for it: https://github.com/Microsoft/TypeScript/issues/2103.