> Avoid vendor locking.

It's open source.

> you can just strip all type annotations with Babel and move on.

Are you implying that this isn't possible with TypeScript?

TypeScript compiles to JS in a straightforward manner as well. If you wanted to move away from TS, you could simply have the TS compiler compile to ES6 and you're done.

But that'd still be transpiled code, right? After getting rid of flow it will be exactly same minus the type annotations. Same cannot be said about typescript considering various language features and syntactic sugar TS offers. Will it run? Yes. Will it feel that it was written by me? That depends.

> Same cannot be said about typescript considering various language features and syntactic sugar TS offers

I think you're vastly misinterpreting what TS is.

It's not anything like CoffeeScript. It's JS plus types and a few other features like Interfaces or advanced ECMAScript features when targetting older versions of the standard.

If you strip away types by exporting to your ECMAScript target of choice, you'll get real JavaScript with the same style as it was written in TypeScript.

It's exactly the same thing you'd get with Flow in that sense. The only additional code you'd get would be for polyfills, but a) those are minimal and b) those will only appear if you export to an older ECMAScript version than the one you wrote it in.

There is no vendor lock.

there are a few minor things like enums and decorators that will need to be compiled because they're not standard and are not just types either (well, const enums are i think?, but the rest are not?).

That's about it though.

Your equivalence with transpiling coffeescript is false. TS doesn't really have "syntactic sugars". Just about everything in it(less the types of course) is pretty far along in the ES adoption process. There are a couple exceptions like decorators that are called out in a very visible manner.

If you target ES6 your code may look identical. Even much of the ES5 down leveling produced code that looks like a person wrote it.

I converted a 10k line coffeescript project(with async/await !) to JS and then TypeScript. The similarities are so far apart they might as well be in different dimensions. But, if you don't want to take a rando posters word for it, it's pretty easy to make a little sample project and see if the output is to your liking.

With target esnext, it produces almost the same output with some spacing differences. Sans the annotations obviously.

That's an objectively incorrect assertion if you're applying that to TypeScript.

The same can be done to it that would be done to Flow: you can just either strip types manually, or just do a single export to your ECMAScripttarget of choice. It'll be native JavaScript. Even the little shims/polyfills it does (to support older ECMAScript versions if you wish to export to it) are optional and can be disabled.

TypeScript has `--target ESNext` this will strip out any TypeScript-specific type annotations, and leave you with standard-track-only JS code that looks identical to your input (modulo type annotations).

If you're afraid of vendor lock-in, but fine with comments then you can just put all of your typing information in jsdoc comments.

https://github.com/Microsoft/TypeScript/wiki/JSDoc-support-i...

FYI we do have an issue open about TS https://github.com/babel/babylon/issues/320 so that we could eventually support TS in Babel as a plugin and then create the same strip-types-plugin just like Flow.

Also, you can progressively opt in to add typing information, while still getting most of the benefits without.

The same can be done with TypeScript. Type inference has been added to it in 2015.

Awesome, did not know this.

Do you have a use case where something would be correctly inferred in Flow but not in TS?

The classic example is:

  function double(x) {
    return x * 2;
  }
  const result = double("foo");

Which passes in TS, but fails in Flow. In TS, the 'x' parameter to the double function is inferred as Any.