A utility type to extract all keys of a given type that are functions

FunctionsOf.ts

/**
 * A utility type to extract all keys of a given type that are functions.
 *
 * @example
 * class Foo {
 *   static bar = 10;
 *   static baz() {
 *     return 'baz';
 *   }
 * }
 *
 * type FunctionOfFoo = FunctionsOf<typeof Foo>; // "baz"
 */
export type FunctionsOf<T> = {
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  [K in keyof T]: T[K] extends (...args: any[]) => any ? K : never;
}[keyof T];