overloads-in-an-interface.ts

function pipe<A>(value: A): A;
function pipe<A, B>(value: A, fn1: (input: A) => B): B;
function pipe<A, B, C>(value: A, fn1: (input: A) => B, fn2: (input: B) => C): C;
function pipe<A, B, C, D>(
  value: A,
  fn1: (input: A) => B,
  fn2: (input: B) => C,
  fn3: (input: C) => D
): D;
function pipe<A, B, C, D, E>(
  value: A,
  fn1: (input: A) => B,
  fn2: (input: B) => C,
  fn3: (input: C) => D,
  fn4: (input: D) => E
): E;
// ... and so on

function pipe(value: any, ...fns: Function[]): unknown {
  return fns.reduce((acc, fn) => fn(acc), value);
}

// BUT YOU CAN DO THIS IN AN INTERFACE AND USE ARROW FUNCTIONS LIKE A SANE PERSON

interface Pipe {
  <A>(value: A): A;
  <A, B>(value: A, fn1: (input: A) => B): B;
  <A, B, C>(value: A, fn1: (input: A) => B, fn2: (input: B) => C): C;
  <A, B, C, D>(
    value: A,
    fn1: (input: A) => B,
    fn2: (input: B) => C,
    fn3: (input: C) => D
  ): D;
  <A, B, C, D, E>(
    value: A,
    fn1: (input: A) => B,
    fn2: (input: B) => C,
    fn3: (input: C) => D,
    fn4: (input: D) => E
  ): E;
  // ... and so on
}

const pipee: Pipe = (value: any, ...fns: Function[]): unknown => {
  return fns.reduce((acc, fn) => fn(acc), value);
};