[chris_st]

I'd love to use TypeScript, but I've hit walls of errors that are nearly as bad as the old C++ template errors! (Though to be fair, this was a while ago, the compiler may have improved).

SO: Any good way to learn TypeScript, particularly the more complicated types?

[acemarke]

What sort of errors are you running into, and what project setup are you using?

If you're using Create-React-App-TS, that's a separate fork of CRA 1.x that adds TS support, and has _horribly_ restrictive lint rules (many common style practices are treated as _compile_ errors). See https://github.com/wmonk/create-react-app-typescript/issues/... for discussion. (I ran across this while trying to set up a TS project for another team.)

I'm happy to see the TS support in CRA 2.x, because now I can actually recommend that people use it to get started with TS support.

I personally had never actually _used_ TS at all until this last week, when I was helping that same team rework some of their code. They'd been slapping `someVar : any` across the entire codebase just to make the compiler shut up. I tried adding a type representing their API response object, added it as a prop to the appropriate React component, and showed them how you could start getting autocomplete and compile-time catching of mistakes, and suddenly they began to see that there were actually benefits of using TS, not just overhead. I'm hoping to try adding TS support in to my own team's codebase in the near future.

[Nican]

I use TypeScript every day, and I like it way better than JavaScript, but here is an example of a bad error message: http://ss.nican.net/photo_2018-10-22_22-09-58.jpg

[acemarke]

Yup, totally agree - that's pretty tough to read.

In that _specific_ example, I think the key part is the "... is not assignable to ServerRoute | ServerRoute[]". It's just giving you all the fields in the type of the object you _are_ returning, and trying to tell you "I can't go from an A to a B". But yes, hard to pick out the key bits of info in there.

[chris_st]

Thanks! I'll give it a go... I was trying with CRA, with the older compiler.

[naiyt]

Have you used TypeScript 3.0? They improved the type errors a lot. I'd highly recommend giving it another shot.

[a_humean]

That was one of the advertised major features for 3.0 and I really like TS, but I haven't noticed a difference.

Still getting frustratingly long and nested error messages that are impossible to read within a tooltip or error pane of vscode. More often than not I just missed or misspelled a single property off an object, but the best source of information for that ctrl+space to see what the non-optional properties are with autocomplete.

Maybe I'm spoilt from what I've seen in Rust and Elm, but either the error messages are useless or I need to copy and paste the tooltip contents into another editor window to spend 5 minutes to decipher them.

It could be that I'm just dealing with complex types with the various libraries I'm using, and so there isn't much TS can do. Some of the React types do seem to get complicated.

[prmph]

One trick I use: start from the bottom of the wall of error messages. Often the root cause of the problem will indicated there.

[emmanueloga_]

Quick q, are the "walls of errors" of errors coming from code you wrote yourself or from 3rd party libraries?

I ask because you say that you want to learn the more complicated types, but I'd say it is better to stick to the basic types for your own code.

It seems obvious to me now, but It took me a while to realize: the reason TS type system is so advanced is to be able to accommodate all the crazy JavaScript APIs that are already out there in the real world. New code doesn't need (and most likely should not) use many of those complicated patterns.

This is also why other compile-to-JS languages have an advantage over TS: they don't have the burden of having to express all the craziness that is JS, and will probably be built around a much simpler/cohesive core of ideas.

TS is still an amazing compiler that provides lots of value: many projects other than TS benefit from TS type definitions. But I'd rather use something else if I'm writing an app from scratch. I'm exploring ClojureScript these days.