(tail) recursive solution to giving change

recursive-change.js

"use strict";

/**
 * The function will use a Greedy method to solve the problem of giving
 * change.
 *
 * @param {Integer} the amount for which we have to give change
 * @param {Array} the values of the coins that are available
 *
 * @return {Array} the list of the selected coins, sorted ascending by value,
 * or an empty array if impossible
 */

function coinChange (amount, coins) {

  // sort coins outside recursive step
  coins.sort((a,b) => b - a);

  return recursiveCoinChange(amount, coins, []);

}

function recursiveCoinChange(amount, coins, used) {
  if(coins.length === 0) {
    return amount > 0 ? [] : used.reverse();
  }

  const biggest = coins[0];
  // first coin won't fit...
  if(amount < biggest) {
    coins.shift();
    // ...so new sub-problem doesn't consider it
    return recursiveCoinChange(amount + 0, coins, used);
  // ...or if it will
  } else if(amount >= biggest) {
    used.push(biggest);
    // use it - we reduce the amount and store and coin
    return recursiveCoinChange(amount - biggest, coins, used);
  } else {
    // otherwise we're done! no coin will fit
    return used.reverse();
  }
}