Typescript useful utility types

utilityTypes.d.ts

type Prefix<TModel extends {}, P extends string> = {
    [Key in string & keyof TModel as `${P}${Capitalize<Key>}`]: TModel[Key];
}

type Suffix<TModel extends {}, S extends string> = {
    [Key in string & keyof TModel as `${Key}${Capitalize<S>}`]: TMOdel[Key];
}

// EnsureProps<{}> = never
// EnsureProps<Person> = Person
type EnsureProps<TModel> = keyof TModel extends never ? never : TModel;

// copied from https://stackoverflow.com/a/69288824/75642
export type Expand<T> = T extends (...args: infer A) => infer R
    ? (...args: Expand<A>) => Expand<R>
    : T extends infer O
    ? { [K in keyof O]: O[K] }
    : never;

export type ExpandRecursively<T> = T extends (...args: infer A) => infer R
    ? (...args: ExpandRecursively<A>) => ExpandRecursively<R>
    : T extends object
    ? T extends infer O
        ? { [K in keyof O]: ExpandRecursively<O[K]> }
        : never
    : T;
    
// Use as:
// type SomeExpandedType = Expand<SomeConvolutedType>;
// type SomeFullyExpandedType = ExpandRecursively<SomeConvolutedType>;

// Returns a union of actual enum type values
type EnumValues<TEnum extends string | number> = `${TEnum}` extends `${infer T extends number}`
    ? T
    : `${TEnum}` extends `${infer T extends string}`
        ? T
        : never;

// returns the enum type if it is one or never if it's not ONLY WORKS FOR enumy of "number" sub-type
type IsTsEnum<T> = [T] extends [number] ? ([number] extends [T] ? T : never) : never;
// example usage to map object properties of enum type to some type:
type EnumMap<TModel> = {
    [K in keyof TModel]: TModel[K] extends IsTsEnum<TModel[K]> ? EnumValues<TModel[K]> : TModel[K];
};