typescript code: transforming object values into keys in typescript

Question

Here is a scenario:

const obj1 = {
  a: 'x',
  b: 'y',
  c: 'z',
}

I am looking to automatically create a type like this:

type Type = {
  x: number,
  y: number,
  z: number,
}

I initially considered the following approach:

type Type = {[key in Object.values(obj1)]: number}

However, it did not work as expected.

SOLUTION

Thanks to @jcalz's assistance, I was able to come up with a generic solution:

type ObjectKeysFromValues<
  O extends { [key: string | number]: string | number},
  V = string,
> = Record<O[keyof O], V>

This can be implemented as shown below:

const obj2: ObjectKeysFromValues<typeof obj1> = {
  x: '1',
  y: '1',
  z: '1',
}

or

const obj2: ObjectKeysFromValues<typeof obj1, number> = {
  x: 1,
  y: 1,
  z: 1,
}

Perhaps I should rethink my naming strategy 😂

Answer 1

Answer №1

To start, make sure to include "as const" after defining obj1.

const obj1 = {
  a: "x",
  b: "y",
  c: "z",
} as const;

Next, there are two ways to define your type.

Option 1 is using index signatures:

type Type = {
    [P in typeof obj1[keyof typeof obj1]]: number
}

Option 2 involves using the built-in utility type "Record" like this:

type Type = Record<typeof obj1[keyof typeof obj1], number>

Answer 2

To start, make sure to include "as const" after defining obj1.

const obj1 = {
  a: "x",
  b: "y",
  c: "z",
} as const;

Next, there are two ways to define your type.

Option 1 is using index signatures:

type Type = {
    [P in typeof obj1[keyof typeof obj1]]: number
}

Option 2 involves using the built-in utility type "Record" like this:

type Type = Record<typeof obj1[keyof typeof obj1], number>