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    Type Alias RequiredKeys<Type>

    RequiredKeys: Type extends unknown
        ? Exclude<keyof Type, OptionalKeysOf<Type>>
        : never

    Extract all required keys from the given type.

    This is useful when you want to create a new type that contains different type values for the required keys only or use the list of keys for validation purposes, etc...

    Type Parameters

    • Type extends object
    import type {RequiredKeysOf} from 'type-fest';

    declare function createValidation<
    Entity extends object,
    Key extends RequiredKeysOf<Entity> = RequiredKeysOf<Entity>,
    >(field: Key, validator: (value: Entity[Key]) => boolean): (entity: Entity) => boolean;

    type User = {
    name: string;
    surname: string;
    luckyNumber?: number;
    };

    const validator1 = createValidation<User>('name', value => value.length < 25);
    const validator2 = createValidation<User>('surname', value => value.length < 25);

    // @ts-expect-error
    const validator3 = createValidation<User>('luckyNumber', value => value > 0);
    // Error: Argument of type '"luckyNumber"' is not assignable to parameter of type '"name" | "surname"'.