var addTwoNumbers = function(l1, l2) {
 
    function printListReverse(list){
        let current = list;
        let digits =[];
        while (current){
            digits.unshift(current.val);
            current = current.next;
            }
        return(parseInt(digits.join("")));  
        }
    

    let listReverse1 = printListReverse(l1);
    let listReverse2 = printListReverse(l2);
    
    let listSum = listReverse1+listReverse2;
    
    
 
    class Node {
        constructor(data, next = null){
            this.data = data;
            this.next = next;
        }
    }
    
    class LinkedList{
        constructor(){
            this.head = null;
        }
    }
    
    let list = new LinkedList();
    
    LinkedList.prototype.insertAtBeg = function (data){
        let newNode = new Node(data);
        newNode.next = this.head;
        
        this.head = newNode;
        
        return this.head;
    }
    
    

    let listArr = String(listSum).split("")
    
    for (digit of listArr){
        list.insertAtBeg(parseInt(digit))
    }
    
  return(list);
}