TS compose fn

compose.ts

type FirstOf<T extends IOFn[]> = T extends [infer F extends (...args: any) => any, ...IOFn[]]
  ? Parameters<F>
  : never
type LastOf<T extends IOFn[]> = T extends [...IOFn[], infer L extends (...args: any) => any]
  ? ReturnType<L>
  : never
type IOFn<I extends any[] = any, O = any> = (...x: I) => O
type Composed<A extends IOFn[]> = (...x: FirstOf<A>) => LastOf<A>

export function compose<A extends IOFn[]>(...fns: A): Composed<A> {
  return (...x: any[]) => fns.reduceRight((acc, fn) => [fn(...acc)], x)[0]
}