compose.js

const f = x => x + 1
const g = x => x * 2
const x = 3

const result = f(g(x)) // 7 


const scream = str => str.toUpperCase()
const exclaim = str => `${str}!`
const repeat = str => `${str} ${str}`

const string = 'Awesome'

const result = repeat(exclaim(scream(string))) //   AWESOME! AWESOME!

const compose = (  ...fns ) => 
  fns.reduceRight( ( acc, fn ) => fn(acc), x )

const enhance = compose( repeat, exclaim, scream )

enhance( string ) // AWESOME! AWESOME!