[treehau5]

- You are writing javascript, not typescript.

- When typescript came out, I was an early adopter, and a lot of it's touted benefits were the class-like syntax and constructors to make it more palatable to enterprise shops (not for me, but it was easier to sell to higher ups), this is mostly a moot point now.

- flow can be attached to any codebase as the codebase stands easily. It is, I have found, difficult to bring TS into an existing project.

- flow fits nicely into existing popular js tooling, mainly babel and react.

- no risk of vendor lock in. Maybe TS compiles to pure 100% syntactically correct javascript today, maybe it doesn't in the future. It isn't javascript, so I won't know.

[whatever_dude]

At the risk of probably repeating myself, allow me to give my $0.02:

> - You are writing javascript, not typescript.

Flow's and TypeScript's distance to JS world are the same, and are very similar in most cases. If you want to add type to one, it's the same as in the other. The only difference here is the file extension, since TS tends to like .ts/.tsx.

> - When typescript came out, I was an early adopter, and a lot of it's touted benefits were the class-like syntax and constructors to make it more palatable to enterprise shops (not for me, but it was easier to sell to higher ups), this is mostly a moot point now.

True, although IMO the greatest feature of TS is making your code stronger, not compiling things that are already part of some ECMAScript version.

>- flow can be attached to any codebase as the codebase stands easily. It is, I have found, difficult to bring TS into an existing project.

True, with TS it's more of a lateral move rather than drops here and there.

>- flow fits nicely into existing popular js tooling, mainly babel and react.

TS works just as well; better, IMO, because dev tools (editors, linters) have better TS support in my experience. Writing React in JS to me makes me feel like I'm using Notepad since there's so much TS helps me with that is lost when using a purely dynamic language.

>- no risk of vendor lock in. Maybe TS compiles to pure 100% syntactically correct javascript today, maybe it doesn't in the future. It isn't javascript, so I won't know.

It does compile to pure JS so ejecting TS is easy; it's trying to follow future standards and proposed changes, not create something different; the project is open source. There is no vendor lock in.

[shados]

There's a few subtle things here. Flow does support annotating types with comments, and can type check React's flowtypes, so you actually can get a fair bit without a compiler at all. In practice, no one does that, so you're still right, but it's worth nothing.

And it's worth noting that TypeScript having its own parser vs the rest of the world using Babel is a pain in the rear. See the time it took for ESLint (having to us TSLint in the meantime), now Prettier, having to use TypeScript with an ES6 target and piping the output in Babel to get proper plugin support, the difference between webpack's resolution mechanism and the one used by TypeScript in tools (an issue Flow also shares), and so on.

Some features like enums (omg, TS enums die die die) namespaces, decorators, and the old module system are also pretty awkward when blending with modern javascript. Makes you want to add lint rules to prevent them from being used.