Ten Years of TypeScript

I tried to port a vanilla js browser game to typescript and I found it introduced a lot of complexity to the project. It sucked me into the npm ecosystem and forced me to rewrite every file to use js modules import/export syntax and a bundler like webpack to resolve all the modules business for browsers when none of those were needed before.

Of course I could set TS modules to none but then I lose access to typing of any third party libraries I'm using like PixiJS.

And my CI pipelines are like 10x slower now because I need npm to install and compile and bundle stuff which is really slow compared to my previous CI pipeline which simply concatenated the js files together with `cat`.

Does this sound right or an I missing something? What I want:

To be able to just type annotate my existing JS without needing modules, but also have TS be able to pull in type information of 3rd party libraries by pointing it to the appropriate .d.ts file. I suppose that's having your cake and eating it too in this case.

Flow's team have made it clear [0] that they don't care about usage outside internal Facebook projects, so since Facebook (from what I hear) uses few external JS dependencies, support for library types is terrible - there's no practical way for library developers to ship Flow types with their library. The third-party flow-typed repository helps somewhat, but relatively few libraries are covered there, so in practice you'll need to write your own typedefs for most libraries you want covered.

When I worked in a Flow codebase, I enjoyed writing Flow types for things, but it was only ever fun in a sudoku-puzzle-solving, Zachtronics-game kind of way. The tools provided were technically enough to express whatever you wanted, but it always took some lateral thinking. TS certainly allows for the same kind of type astronautery, but as a non-library app developer you never have to resort to that; you can always fall back to something slightly less strict that covers you from most real-world problems without the all-or-nothing strictness Flow mandates. In the end I was the last holdout on the team advocating for not migrating to TS. The migration went well and the team was more productive for it.

It's fun to think about an alternate universe where Facebook gave Flow the investment and community support it deserved, and today it's part of a beautiful React/Flux/Jest/Flow/Reason ecosystem (eventually leading to a complete takeover of the browser frontend by Ocaml). For real work, though, Typescript gets the job done.

[0] https://medium.com/flow-type/clarity-on-flows-direction-and-...

* "Impose no runtime overhead on emitted programs." * "Align with current and future ECMAScript proposals." * "Preserve runtime behavior of all JavaScript code." * "Avoid adding expression-level syntax." * "Use a consistent, fully erasable, structural type system."

I also really liked the callout of their approach to "innovating in the type system around conventions and patterns found 'in the wild' of the JavaScript ecosystem."

This "you can still write the JS-style APIs you want, just safely" is a stark contrast to the Dart/ActionScript/others options mentioned in the HN thread, which said "you have to give up the JS-style APIs you have, and instead write 'basically Java'".

It's also amazing how TS 1.x itself was "basically Java" (in terms of a type system, albeit except being structural), but so many of the TS 2.x type systems innovations (mapped types, conditional types, etc) look as if they were designed in the language from day 1.

One other point, the post calls out they didn't add extra syntax to JS, only types; in this regard, I think TypeScript frankly got lucky by how much JavaScript itself has evolved in the last 10 years. Like if JS had been going through a "10 years of sterility" period like Java did from ~2005-2015, then TS itself would have been greatly hindered and probably would have had to jump to syntax-level changes, like the Scalas and Koltins and other Java.nexts had to do.

So, kudos to JS itself for also evolving extremely well from its ~2010 everything-is-a-callback early days, and letting TS stand on its shoulders.