addTwoNumbers.js

//////////////////////////////////////////////Add Two Numbers///////////////////////////////////////////////////////
// You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order,
// and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.
// You may assume the two numbers do not contain any leading zero, except the number 0 itself.
// Example 1:
// Input: l1 = [2,4,3], l2 = [5,6,4]
// Output: [7,0,8]
// Explanation: 342 + 465 = 807.
// Example 2:
//
// Input: l1 = [0], l2 = [0]
// Output: [0]
// Example 3:
//
// Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
// Output: [8,9,9,9,0,0,0,1]
//
//
// Constraints:
//
// The number of nodes in each linked list is in the range [1, 100].
// 0 <= Node.val <= 9
// It is guaranteed that the list represents a number that does not have leading zeros.
function ListNode(val, next) {
    this.val = (val === undefined ? 0 : val)
    this.next = (next === undefined ? null : next)

}
const addTwoNumbers = function(l1, l2) {
   let carry = 0, sum = 0, l3 = new ListNode(), newNode = l3;

   while (l1 || l2) {
       let newL1 = (l1 !== null) ? l1.val : 0;
       let newL2 = (l2 !== null) ? l2.val : 0;
       let result = (newL1 + newL2 + carry);
       sum = result % 10;
       carry = Math.trunc(result / 10);

       if (l1 != null) {
           l1 = l1.next;
       }

       if (l2 !== null) {
           l2 = l2.next;
       }

       l3.next = new ListNode(sum);
       l3 = l3.next;
   }

   if (carry > 0) {
       l3.next = new ListNode(carry);
   }

   return newNode.next;
};

// console.log(addTwoNumbers([2,4,3], [5,6,4]));