Demonstrando o poder da composição com fold

comp.js

const def =  ( x ) => typeof x !== 'undefined'
const identityFn =  ( x ) => x
const compose =  ( f, g ) => ( x ) => f( g( x ) )
const fold =  ( fn, acc, [ x, ...xs ] ) =>
  def( x ) && fold( fn, fn( acc, x ), xs ) || acc

const addOne =  ( x ) =>  x + 1
const timesTwo =  ( x ) =>  x * 2
const addThree =  ( x ) =>  x + 3

const functions = [ addOne, timesTwo, addThree ]

const composeMany =  ( xs ) => fold( compose, identityFn, xs )
const outputFn = composeMany( functions )

outputFn( 2 )