Cannot find issue with function for iterating array numbers, adding them, evaluating, and returning largest index.

var cards = 
    ['5865-2600-5889-0555', '4779-598666-3666', '4252-278553-7978' ,'4556-4242-9283-2260'];  // card numbers used console.log(cards, "1");  // raw data

  function maxCardSum(card){             // function...returns card when called
  var resultMaxSum = 0;                       // max sum of card to be used
  var currentSum = 0;                          // counter of current card add
  var newCards = [];                            // reassigning modified cards to array
  var resultCard;

  for (var i = 0; i < cards.length; i++){            // iterate through 
    newCards[i] = cards[i].replace(/-/g, ""); // R&R dashes with ""
    console.log(newCards[i], "2");               // update ... string
    newCards[i] = newCards[i].split("");     // split to separate
    console.log(newCards[i], "3");             // update now an object   
    //newCards[i] = newCards[i].toString();
    // console.log(typeof newCards[i], "4");
   // for loop on the cards
       for (var j = 0; j < newCards.length; j++){    // nested loop
       console.log(newCards[j], "5");                // currently an object
       currentSum += parseInt(newCards[j]);           // adding all on string to currentSum ... does not work...
       console.log(newCards[j], "6");                   // update object
       console.log(currentSum, "7");                    // update number
       } if (resultMaxSum <= currentSum){
             resultMaxSum = currentSum;                 // biggest card updated to this
             resultCard = cards[i];}                    // calculation of max reassigned
   }
   return resultCard;                                       // returns resultCard as qualifying card
}
 maxCardSum(cards);                                       // function maxCardSum,  pass in cards
console.log("The credit card number with the max sum of all numbers is: " + resultCard);