Fun JavaScript stuff

doubleList.js

// Old, imperative way
const originalDoubleList = list => {
  const newList = [];
  for (let i = 0; i < list.length; i++) {
    newList[i] = list[i] * 2;
  }
  return newList;
};

console.log(originalDoubleList([20]));

// New, declarative way with a twist ;)
const doubleList = list => list.myMap(x => x * 2);

const box = value => ({
  myMap: f => box(f(value)),
  toString: () => `box value: ${value}`
});

const tmp = doubleList(box(20));

console.log(tmp.toString());