[Typescript]106. Medium - OnPropChnagedMethods

type OnPropChnagedMethods<T> = {
  [Key in keyof T & string as `${Key}Changed`]: (cb: (newValue: T[Key]) => void) => void
}
declare function makeWatchedObject<T>(obj: T): T & OnPropChnagedMethods<T>;
let homer = makeWatchedObject({
  firstName: "Homer",
  age: 33,
  location: "Springfield"
})