Custom utility type to filter or remove types

custom-typefilter.ts

// Playground: https://www.typescriptlang.org/play/?#code/PTAEBUE8AcFNWgJwPYHNEEMC2WCWA7VAKBFAHFkMAbALlADNcqAXWRUDUACgGdZnQyegEpQzGLB4MUWDvmTMAFmzESSYRc2bQeNEACMqaAHQBrXEmQ9FxgMbIswWwFcezBwFpnzJrnEfxOB4PAgCJHltEC2ZgIiJA+AAFNh5kfABJfHpkUABeUABvIlBQfGxYOjcowgBuYo5UCtLnLH02OpLoRTSm-Ba2xA7QAEdnBSaqglQhgHdkRFM6LlFcgD5QADdkXAATIgBfOviJUAAlWCxkDdgAaVhIHgB5eig4AB5X2AAaUDvIdfyRRKAG1TPdQARQGDIEIICcMFJPqD7gBdUCwAAerHwOykf1AAH5SrBruw6NCUXQkRS6oc4glQAAxJisRB-J4vCQfCQ-P4Awr1ZGQCH4KH3WGfDiIiRCtGY7G437gonQ0B0fAktiUuFwWW0o7HOCgADqfm63gAcv0Unkzhcrrd7hzPm9kohUhkssgfn1WmxVkcGY98FRIFa-e7bcyWGx2c8XW6PZlsj7rYgA-STsHQ+GBjwAII4gDKzGqqCk+WjrLjnPeibSye9zQjoAAPqBJoRVkQgA

// Type programming
// Goal: filter a (set of) types from another type
// https://blog.kiprosh.com/custom-utility-types-in-typescript/

type PersonInfo = {
  name: string;
  age: number;
  phone: number;
  quote: string;
  work: () => void
};

type RemoveKeysOfType<Type, Key> = {
  [key in keyof Type as Type[key] extends Key ? never : key]: Type[key];
};

type FilterKeysOfType<Type, Key> = {
  [key in keyof Type as Type[key] extends Key ? key : never]: Type[key];
};


type WithoutNumbers = RemoveKeysOfType<PersonInfo, number>;

type OnlyNumbers = FilterKeysOfType<PersonInfo, number>;

type OnlyNumbersAndStrings = FilterKeysOfType<PersonInfo, number | string>