coinSum.js

function coinSum(amount) {
  return getCount([200, 100, 50, 20, 10, 5, 2, 1], amount);
}

const getCount = memoize((setOfCoins, value) => {
  if (setOfCoins.length === 0 || value < 0) return 0;
  if (value === 0) return 1;
  
  var largestCoinInRemainingSet = setOfCoins.slice(0,1);
  var remainingCoins = setOfCoins.slice(1);
  return getCount(remainingCoins, value) + getCount(setOfCoins, value - largestCoinInRemainingSet);
})

function memoize(fn) {
  var memory = {};
  return function(arg1, arg2) {
    var inputString = `${arg1} ${arg2}`
    var answer = memory[inputString]
    if (answer) return answer
    else {
      answer = fn(arg1, arg2);
      memory[inputString] = answer;
      return answer
    }
  }
}