### 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->4Output: 1->1->2->3->4->4

### analyze

/** * 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 dummyLink = new ListNode(0)  let cur = dummyLink  let l1Point = l1  let l2Point = l2
while (l1Point && l2Point) {    if (l1Point.val < l2Point.val) {      cur.next = l1Point      l1Point = l1Point.next    } else {      cur.next = l2Point      l2Point = l2Point.next    }    cur = cur.next  }
while (l1Point) {    cur.next = l1Point    cur = cur.next    l1Point = l1Point.next  }
while (l2Point) {    cur.next = l2Point    cur = cur.next    l2Point = l2Point.next  }
return dummyLink.next}

/** * 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) {  if (l1 === null) {    return l2  }  if (l2 === null) {    return l1  }  if (l1.val < l2.val) {    l1.next = mergeTwoLists(l1.next, l2)    return l1  } else {    l2.next = mergeTwoLists(l1, l2.next)    return l2  }}