Typescript remap Array Type

Question

Is it possible to remap type of array (or maybe tuple?)

Let's say that I have an array of functions and I want to make of it array of functions captured parameters. Something like.

type Remap<F extends ((... args: any) => any)[]> =
    F extends [infer T1] ? [Parameters<T1>] :
    F extends [infer T1, infer T2] ? [Parameters<T1>, Parameters<T2>] :
    F extends [infer T1, infer T2, infer T3] ? [Parameters<T1>, Parameters<T2>,  Parameters<T3>] :
    never;

const a = [(a: string) => void, (b: number) => void]
type T = Remap<typeof a> // [[string], [number]] - simply captured arguments of functions.

What i need to is pass array of functions like "a" and create maybe new function which will contain parameters from all functions like ([first arguments], [second arguments]).

Titian Cernicova-Dragomir · Accepted Answer · 2019-12-17 20:27:07Z

1

You can use a mapped type to map a tuple:

type Remap<F extends ((...args: any) => any)[]> = {
  [P in keyof F]: F[P] extends (...a: infer P) => any ? P: never
}

declare const a: [(a: string) => void, (b: number) => void]
type T = Remap<typeof a>

Playground Link

edited Dec 17, 2019 at 20:27

answered Dec 17, 2019 at 20:21

Titian Cernicova-Dragomir

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3 Comments

Titian Cernicova-Dragomir Over a year ago

@luky wops, initially repasted the same code..hope you saw the updated mapped tuple version (it was always in the playground link..)

luky Over a year ago

yes i saw it there, but first i was looking for the changes :)

luky Over a year ago

and (...params: T) is [[string], [number]] and if i wanted [string, number]?

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