sum and reducer.js

var summer = function(old_sum, old_input) {
  return old_sum + (old_input % 10);
}

var reducer = function(old_input) {
  return old_input / 10;
}

var calculateSum = function(input) {
  var sum = 0;
  while (input > 0) {
    sum += summer(sum, input);
    input = reducer(input);
  }
  
  return sum;
}