monolith-vs-composition.js

const monolith = () => {
  var mutable = 10;
  var sum = 0;
  while (mutable !== 0) {
    if (mutable % 2 === 0) {
	sum += mutable;
    }
    mutable -= 1;
  }  
  return sum;
}


const generateList = n => Array.from(Array(n).keys())
const isEven = n => n % 2 == 0
const filter = f => xs => xs.filter(f)
const sum = xs => xs.reduce((acc, val) => acc + val)
const compose = (f, g) => x => f(g(x))

const composition = () => compose(sum, filter(isEven))(generateList(11))