let changeMapping = [];
changeMapping.push(createChangeObj("twentyDollar", 2000));
changeMapping.push(createChangeObj("tenDollar", 1000));
changeMapping.push(createChangeObj("fiveDollar", 500));
changeMapping.push(createChangeObj("twoDollar", 200));
changeMapping.push(createChangeObj("oneDollar", 100));
changeMapping.push(createChangeObj("quarter", 25));
changeMapping.push(createChangeObj("dime", 10));
changeMapping.push(createChangeObj("nickel", 5));
changeMapping.push(createChangeObj("penny", 1));

var createChangeObj = function(key, value) {
  let changeObj = {};
  changeObj.key = key;
  changeObj.value = value;
  return changeObj;
};

var calculateChange = function(total, cash) {
  if (cash <= total) {
    // Cash given is less than total owed.
    return {};
  }

  let retChangeObj = {};
  let difference = cash - total;
  for (let changeObj of changeMapping) {
    let val = changeObj.value;
    // This denomination is greater than amount remaining
    let numDenom = 0;
    while (val <= difference) {
      difference -= val;
      numDenom++;
    }

    if (numDenom > 0) {
      retChangeObj[changeObj.key] = numDenom;
    }
  }
  return retChangeObj;
};

var runTask4 = function() {
  console.log(calculateChange(1787, 2000));
  console.log(calculateChange(2623, 4000));
  console.log(calculateChange(501, 1000));
  /*
    { twoDollar: 1, dime: 1, penny: 3 }
    { ten: 1, twoDollar: 1, dollar: 1, quarter: 3, penny: 2 }
    { twoDollar: 2, quarter: 3, dime: 2, penny: 4 }
    */
};

runTask4();