Type Alias ReadonlyKeysOf<T>

ReadonlyKeysOf: NonNullable<
    {
        [P in keyof T]: IsEqual<
            { [Q in P]: T[P] },
            { readonly [Q in P]: T[P] },
        > extends true
            ? P
            : never
    }[keyof T],
>

Extract all readonly keys from the given type.

This is useful when you want to create a new type that contains readonly keys only.

Type Parameters

Example

import type {ReadonlyKeysOf} from 'type-fest';

interface User {
	name: string;
	surname: string;
	readonly id: number;
}

type UpdateResponse<Entity extends object> = Pick<Entity, ReadonlyKeysOf<Entity>>;

const update1: UpdateResponse<User> = {
    id: 123,
};

Type Alias ReadonlyKeysOf<T>

Type Parameters

Example

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