addtwonumslinkedlists.js

function addTwoNumbers(l1, l2) {
  let carry = 0;
  let result = new ListNode(0);
  let current = result;

  while (l1 || l2) {
    let sum = (l1 ? l1.val : 0) + (l2 ? l2.val : 0) + carry;
    carry = sum >= 10 ? 1 : 0;
    current.next = new ListNode(sum % 10);
    current = current.next;
    if (l1) l1 = l1.next;
    if (l2) l2 = l2.next;
  }

  if (carry) {
    current.next = new ListNode(1);
  }

  return result.next;
}

// Assuming that the linked list nodes are represented by the following class:

class ListNode {
  constructor(val = 0, next = null) {
    this.val = val;
    this.next = next;
  }
}

// You can call the function by creating two linked lists and passing them as arguments:
let l1 = new ListNode(2, new ListNode(4, new ListNode(3)));
let l2 = new ListNode(5, new ListNode(6, new ListNode(4)));
let result = addTwoNumbers(l1, l2);
console.log(result); // should print: ListNode { val: 7, next: ListNode { val: 0, next: ListNode { val: 8, next: null } } }