Typescript creating Object Type from Readonly Array

Question

I have an array like so:

const arr = [{id: 2, name: "hotdog"}, {id: 3, name: "chicken"}] as const

And I want to generate a type from it, that looks like this:

type ArrTransform = { readonly hotdog: 2, readonly chicken: 3 }

I've tried to do something like this (and many other attempts, but this was the closest I could get):

type ArrToObject<T extends ReadonlyArray<{name: string, id: number}>> = {
  [key in T[number]["name"]]: T[number]["id"]
}

But it doesn't map names with the exact id, it generates a union from all the ids (2 | 3) - which is not what I want.

Is it even possible to create a generic like this in Typescript?

CertainPerformance · Accepted Answer · 2022-04-19 01:03:19Z

3

Access each whole individual object with only [number], then separately extract the name property (assert that it'll be the key with as) and the id after the colon.

type Obj = {
    [T in typeof arr[number] as T["name"]]: T["id"]
}

answered Apr 19, 2022 at 1:03

CertainPerformance

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2 Comments

Bbrk24 Over a year ago

It is possible to make a generic version as well: playground link

moomoolive Over a year ago

Damn this is good! What is this sorcery? Also thanks a ton @Bbrk24, your playground link was more or less exactly what my actual use case is.

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