Functional Solution

[nelsonic]

Can we write a purely functional solution to get beginners used to the idea of writing functional code?

[nelsonic]

Helpful links:

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Map
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill
• Extended example: https://www.sitepoint.com/map-reduce-functional-javascript

[nelsonic]

const COINS = [200, 100, 50, 20, 10, 5, 2, 1]; // "constant" of all coins

function getChange (payable, paid) {
  return COINS.reduce((change, coin) => {
    const change_sum = change.reduce((sum, coin) => sum + coin, 0);
    const remaining = paid - payable - change_sum;
    const times_coin_fits = Math.floor(remaining / coin);
    return change.concat(Array(times_coin_fits).fill(coin));
  }, []); // change array starts out empty and gets filled itteratively.
}

I don't think Array.fill is "purely functional" because it mutates the array in-place, but I can't think of how else to do it ... 🤔