/**
 * Merge Two Sorted Lists
 *
 * Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the
 * nodes of the first two lists.
 *
 * Example:
 *
 * Input: 1->2->4, 1->3->4
 * Output: 1->1->2->3->4->4
 */

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
  const temp = new ListNode(0);
  let p = fakeHead;

  while (l1 && l2) {
    if (l1.val < l2.val) {
      p.next = l1;
      l1 = l1.next;
    } else {
      p.next = l2;
      l2 = l2.next;
    }
    p = p.next;
  }

  if (l1) {
    p.next = l1;
  } else if (l2) {
    p.next = l2;
  }

  return temp.next;
};

export { mergeTwoLists };

/**
 * Merge Two Sorted Lists
 *
 * Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the
 * nodes of the first two lists.
 *
 * Example:
 *
 * Input: 1->2->4, 1->3->4
 * Output: 1->1->2->3->4->4
 */

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
  const temp = new ListNode(0);
  let p = temp;

  while (l1 && l2) {
    if (l1.val < l2.val) {
      p.next = l1;
      l1 = l1.next;
    } else {
      p.next = l2;
      l2 = l2.next;
    }
    p = p.next;
  }

  if (l1) {
    p.next = l1;
  } else if (l2) {
    p.next = l2;
  }

  return temp.next;
};

export { mergeTwoLists };

Fix variable name