Simple composition helper for FP in ES6.

es6-simple-compose.js

const compose = (...callbacks) => (
  (...args) => (
    callbacks.reduce((prev, callback) => (
    	[callback(...prev)]
    ), args)
  )
);

compose(
  (x) => (x * 2),
  (x) => (x * 3),
  (x) => (x * 4)
)(2);