KnowKeys

[mdbetancourt]

🍩 Feature Request

Is your feature request related to a problem?

To get only know keys of an object

Describe the solution you'd like

type KnownKeys<T> = {
  [K in keyof T]: string extends K ? never : number extends K ? never : K
} extends { [_ in keyof T]: infer U } ? U : never;

https://stackoverflow.com/a/51956054/8741524

[millsp]

Approved. This can benefit all the ...Keys utilities too, since they return never in the case outlined on StackOverflow.

export type _KnownKeys<O extends object> = {
    [K in keyof O]-?: string extends K
                      ? never
                      : number extends K
                        ? never
                        : K
} extends {
    [K in keyof O]: infer K
} ? K & keyof O : never

And we could rewrite other utilities such as:

export type _RequiredKeys<O extends object> = {
    [K in keyof O]-?: string extends K
                      ? never
                      : number extends K
                        ? never
                        : K
} extends {
    [K in keyof O]: infer K
} ? K & keyof O : never

Thanks!

[mdbetancourt]

Approved. This can benefit all the ...Keys utilities too, since they return never in the case outlined on StackOverflow.

yes i had to use it with SelectKeys in order to work properly

[millsp]

Would you mind posting an example?

[mdbetancourt]

i'm using an ORM so i created

export type PrimaryID<T> = Any.Type<T, 'PrimaryID'> & ID<T>

type KnownKeys<T> = {
  [K in keyof T]: string extends K ? never : number extends K ? never : K
} extends { [_ in keyof T]: infer U }
  ? U
  : never

export type OnlyDeclared<T> = Pick<T, KnownKeys<T>>

export type GetPrimaryID<T extends object> = T[Object.SelectKeys<
  OnlyDeclared<T>,
  PrimaryID<{}>
>]

export type TypeOfPrimaryID<T extends object> = GetPrimaryID<T> extends PrimaryID<infer X>
  ? X
  : never

export class User {
  id: PrimaryID<string>
  name: string
  age: number
  phones: Phone[]
  [prop: string]: unknown
  constructor(data: Partial<User>) {
    super(data)
  }
}
function findById(id: TypeOfPrimaryID<User>) {}