Sleutels hernoemen met as in mapped types

type Prefixed<T> = {
  [K in keyof T as `prefix_${string & K}`]: T[K]
};
type P = Prefixed<{ name: string }>;
// { prefix_name: string }

type OnlyStrings<T> = {
  [K in keyof T as T[K] extends string ? K : never]: T[K]
};

type Getters<T> = {
  [K in keyof T as `get${Capitalize<string & K>}`]: () => T[K]
};
type UserGetters = Getters<{ name: string; age: number }>;
// { getName: () => string; getAge: () => number }

type Setters<T> = {
  [K in keyof T as `set${Capitalize<string & K>}`]: (val: T[K]) => void
};

type Invert<T extends Record<string, string>> = {
  [K in keyof T as T[K]]: K
};

type MethodKeys<T> = {
  [K in keyof T as T[K] extends Function ? K : never]: T[K]
};

type Namespaced<T, NS extends string> = {
  [K in keyof T as `${NS}::${string & K}`]: T[K]
};

type FormFields<T> = {
  [K in keyof T as K extends string ? K : never]: string
};