added Description

Author: mauricechouam

Add Two Numbers/code.js

@@ -0,0 +1,28 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/*
+ * @param {ListNode} l1
+ * @param {ListNode} l2
+ * @return {ListNode}
+ */
+var addTwoNumbers = function(l1, l2) {
+    const beforeHead = new ListNode();
+ let curr = beforeHead;
+ let carry = false;
+ while (l1 || l2 || carry) {
+   const a = (l1 || 0) && l1.val;
+   const b = (l2 || 0) && l2.val;
+   const sum = a + b + carry;
+   curr.next = new ListNode(sum % 10);
+   curr = curr.next;
+   l1 = l1 && l1.next;
+   l2 = l2 && l2.next;
+   carry = sum >= 10;
+ }
+ return beforeHead.next;
+};