function_composition-pipe.js

// reference https://medium.com/javascript-scene/master-the-javascript-interview-what-is-function-composition-20dfb109a1a0

const pipe = (...fns) => x => fns.reduce((v, f) => f(v), x);

const fn1 = s => s.toLowerCase();
const fn2 = s => s.split('').reverse().join('');
const fn3 = s => s + '!'

const newFunc = pipe(fn1, fn2, fn3);
const result = newFunc('Time'); // emit!