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Comment by vinnymac | Hacker News Reader

I think they are referring to the manual creation of type definitions. As they mention it in the article.

But then they assume the code is authored in Typescript... Who is authoring in Typescript and then simultaneously writing their d.ts manually?? It makes no sense.

I write all my d.ts files manually. Maybe that’s the problem: people don’t know how to write TS, expect some software to do it for them, and then end up waiting hours on a build that should take 10 seconds.

This confuses me. You either write the d.ts manually before build, which only makes sense if you wrote the original code in JavaScript (not Typescript) or you write the source in Typescript and enable the declaration option in your tsconfig and the d.ts pops out in seconds along with your final JS output.

Unless you are using transpileOnly, generating declarations will not make a few second build become a few hours-- Typescript is already type checking your code.

I write TypeScript projects in TypeScript from the start. If I have an existing JS project that needs to port to TypeScript then I will rewrite it entirely in TypeScript. Yes, that takes some small amount of time, but it’s never a complete rewrite. It’s mostly just minor syntax updates as the actual runtime should remain the same as validated by test automation.

I type everything I declare whether a primitive or not. My complex types like data structures, objects, and modules get typed as interfaces. I write them as I need them. I also have lint rules that check for missing type declarations.

Don’t over think any of this. None of this exists as an exercise in code masturbation. There are two immediate values to TS: warning on unintended type coercion and predictive rapid refactoring. So, just keep plan your software appropriately and keep everything simple.

But why would any of that need to be done manually in a .d.ts file? You can just write your type definitions in ts files

Types are meta data for the compiler. They are not code that is compiled to JavaScript, so I isolate my type definitions to d.ts files. That is the only reason I have d.ts files at all.

Types are also documentation for the developers reading and editing the code.

Maybe if writing .d.ts-es by hand was a proper way to write TS, people would know about that from the docs. Don’t sell your fetishes as some sort of a common knowledge please, it doesn’t help anyone.

Writing types yourself may or may not be the best approach. Everybody is entitled to their opinions. However, builds that take more than 30 seconds (and that is extremely forgiving) is ridiculously wrong.

So, my very best recommendation is to turn that frown upside down and measure things. This is called total cost of ownership (TOS). If the cost of manually writing types is less than the total cost of running builds in a week you then it is absolutely the most correct approach.

https://en.wikipedia.org/wiki/Total_cost_of_ownership

As far as fetishes go I try to avoid logical fallacies like you recommended for me: https://en.wikipedia.org/wiki/Argumentum_ad_populum

Author here. Unfortunately, I think worded that a bit confusingly in the article. I'm used to working with runtimes that run TS natively and didn't have to care about .d.ts files myself for a long time. From that perspective creating them by running the tsc compiler feels like a manual step for me.

There are cases where folks write them by hand, but that's not what I had in mind when writing the article. I've rephrased that part a bit to hopefully make it less confusing.

Thanks for the clarification.

The fact that there are developers out there that are willing to accept hour long compile times from the typescript compiler is disgusting. I’ve seen slow recursive types here and there, but you can analyze your slow types using tsc and fix them yourself.

I hope that slow typescript compiling is a niche issue for massively large/complex codebases and not a common problem.

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