fp.js

const pipe = (...args) => val => args.reduce((a,b) => b(a), val);
const foldl = fx => init => arr => [].reduce.call(arr, fx, init);
const fmap = fx => arr => [].map.call(arr, fx);

const arr = [1, 2, 3];

const fx1 = a => a * 2;
const fx2 = a => a - 2;
const fx3 = a => a * a;
const fx4 = (a, b) => a + b;

const piped = pipe(fx1, fx2, fx3);
const myMap = fmap(piped); 
const myFoldl = foldl(fx4)(100); 
const final = pipe(myMap, myFoldl);

console.log(final(arr)); // 120