Typescript: example of lesser number of parameters as a narrow type.

less-params-narrow-type.ts

interface CallbackWithNameParameter {
  cb: (name: string) => void
}

type CallbackWithNoParameter = () => void;
const aCallbackWithNoParameter: CallbackWithNoParameter = () => {};

const aCallback: CallbackWithNameParameter = { // okay
  cb: aCallbackWithNoParameter
};
aCallback.cb(); // error

const aSecondCallback: CallbackWithNameParameter = { // error
  cb: (num: number) => {}
};