re: TypeScript is a waste of time. Change my mind. VIEW POST

re: Uh, wait why are you using a single variable across 78 files? If I have to understand 78 files to understand a feature it sounds like you have bigg...

That’s a lot of judgement Jordan. You seem to be making some assumptions.

“uh, wait why are you using a single variable across 78 files? If I have to understand 78 files to understand a feature it sounds like you have bigger problems.”

For a moment, suspend your assumptions and consider the fact that we had a valid reason for updating the the name of a property on some data. The reason the variable change effected 78 files is because we renamed a property on a data object that we use throughout the entire system. And since we have many api tests, end-to-end tests, unit tests, and more it caused a large change. But that’s the beauty of TypeScript... I can make a change that effects the entire system without causing any quality concerns.

So while your assumptions involve a change to one feature, in reality this change effected all features. When you take a functional / data-oriented approach it’s not uncommon to have many transformation functions that manipulate the data. And since I currently work on a data visualization UI, there are a great many ways that the users want the data to be transformed.

Does that clarify how one variable name can ripple out? Hopefully it communicates how TypeScript allows my team to continuously refactor with safety and without having to spend a bunch of time updating tests just because we learned that we originally misspelled a property on the data an API returns.

Yeah, you're right I did judge. Sorry. I don't know your codebase, I just find it odd that a single variable would exist across 78 files. Feels wrong to me. Something like KISS or maybe SRP come to mind. But again I don't know your codebase.

I think what they were doing is renaming a key in an interface, like going from data.online to data.isOnline

Or adding data.timestamp. With TS you automatically get notified of all the places where this data has to be set and also you now automatically know everywhere you use data that it also has a timestamp property. Also, TS ecosystem goes further than that, you could have Protobuf definitions that might be updated because data is serialized and sent over the network to multiple other services, and with the updated TS typings everyone just knows about this change and can update their code accordingly. And yes, this data interface could be used by hundreds of files across multiple services and git repos.

Vscode refactors plain js just fine. Typescript does not help with that.

Actually, I might be mistaken, but VSCode uses tsserver to better understand your code and do stuff like refactoring, IntelliSense and stuff.

TypeScript isn't only able to perform static type checking on explicit types, it also infers types quite well. It's even possible to write plain JS, enable allowJs and checkJs on your tsconfig.json and let it infer and type-check stuff for you.

This also takes me to another point: in my experience I hardly type stuff other than function parameters; typescript can, usually, infer the rest. So arguments like "you write more code" get a bit weaker, IMHO

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