Add solution #2

Author: JoshCrozier

solutions/0002-add-two-numbers.js

@@ -4,8 +4,9 @@
  * Difficulty: Medium
  *
  * 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.
+ *
+ * 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.
  */
@@ -24,19 +25,13 @@
  */
 var addTwoNumbers = function(l1, l2) {
   const result = new ListNode();
-  let tail = result;
-  let carry = 0;
-
-  while (l1 || l2 || carry) {
-    const v1 = l1 ? l1.val : 0;
-    const v2 = l2 ? l2.val : 0;
-    const v = v1 + v2 + carry;
 
-    tail.next = new ListNode(v % 10);
+  for (let tail = result, carry = 0; l1 || l2 || carry;) {
+    const value = (l1?.val ?? 0) + (l2?.val ?? 0) + carry;
+    tail.next = new ListNode(value % 10);
     tail = tail.next;
-    carry = v >= 10 ? 1 : 0;
-    l1 = l1 && l1.next;
-    l2 = l2 && l2.next;
+    carry = value >= 10 ? 1 : 0;
+    [l1, l2] = [l1 && l1.next, l2 && l2.next];
   }
 
   return result.next;