[russley]

There have been several projects that were flow based that have moved to TS. I think the real litmus test will be if React eventually either includes TS types or is rewritten in TS.

Disclaimer: I work with TypeScript professionally.

[acemarke]

I'm pretty in tune with what's going on around React, and I don't see that one ever happening.

The React team is _very_ busy already with work around Hooks, Concurrent Mode, and Suspense. There's no way they're going to pause development on implementing all these major chunks of functionality just to rewrite from one type system to another.

I've seen Dan express some frustration with Flow's pace of development on Twitter a couple times, but beyond that, no indications whatsoever that React would be converted to TS. In the entirely hypothetical scenario that React _did_ get rewritten to another language, I have to assume it would be something like ReasonML (which was created by Jordan Walke, the original creator of React).

[52-6F-62]

One of the benefits to TypeScript is that the codebase wouldn't need to be rewritten.

A declaration file(s) could be included. There they could just declare types for all classes, methods, constants, etc. Similar to C header files.

(This is how the DefinitelyTyped repository handles typings for untyped source repositories: https://github.com/DefinitelyTyped/DefinitelyTyped)

Ex:

JavaScript: app.js

    function app(arg1, arg2, arg3) {
       // does something
       return {
          key1: someStringValue,
          key2: someNumberValue,
       };
    }

TypeScript: app.d.ts

    declare type AppReturnValue = { key1: string, key2: number };
    declare function app(arg1: string, arg2: string[], arg3: boolean): AppReturnValue;

[acemarke]

Given that React is already heavily invested in Flow types, there would be _some_ form of rewrite.

And like I said, Flow is providing sufficient benefit for the React team right now, and their focus is on expanding React's capabilities. Changing type systems is not on their radar as far as I know.

[52-6F-62]

Oh— can you point me at a file in particular? I had a look around the codebase and didn't see anything but plain JS. Might have been looking in the wrong places.

And I certainly get your point. However I wonder if they'd consider community-contributed TypeScript declaration files to the official repo as they wouldn't cause conflicts with the Flow system—

[acemarke]

Flow types are _everywhere_ in the codebase.

To pick a specific example, here's the file that implements the core logic for the new Hooks feature:

https://github.com/facebook/react/blob/6cb26774e27e03c7d5d6e...

As for the TS typings, there's been lots of agitation from people asking them to be officially included and shipped with React. But, again, the React devs themselves aren't TS users (that I know of), and so they don't have the expertise to write and maintain those typings. Better that they be left over in DefinitelyTyped for the community to maintain.

(I'm a Redux maintainer, and I feel exactly the same way about the typings for React-Redux. I don't have any actual TS experience myself yet, and I couldn't do anything useful in regards to the React-Redux typings. Plus, I've got far too much else on my plate to worry about those.)