TIL: `satisfies` is my favorite TypeScript keyword

Re:TIL: `satisfies` is my favorite TypeScript keyword by kennywinker on Sunday November 23, 2025 @03:29AM (#46021770)

Ah, yeah you’re right. I somehow thought typescript could do type narrowing based on checks - like say:

If (i >= 1) { // i’s type now includes >= 1 }

But that is not the case, so you’d need a single cast to make it work (from number to ClampedNumber<1,200>) or however exactly you’d want to express this.

Tbf having looked more closely into how typescript handles number range types, I don’t think I would ever use them. Not very expressive or clear. I think I hallucinated something closer to what is in this proposal: https://github.com/microsoft/TypeScript/issues/43505

I still think that the general idea of communicating what acceptable input is via the type system is a good one. But the specifics of doing that with numbers isn’t great in typescript yet.

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Re:TIL: `satisfies` is my favorite TypeScript keyword by samdoesnothing on Sunday November 23, 2025 @04:09AM (#46021943)

How would you implement it in other languages that support it better? Can you literally just do a range check and the compiler infers its range for types? If so thats actually pretty neat.

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