### 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``````

### analyze

``````/**
* function ListNode(val) {
*     this.val = val;
*     this.next = null;
* }
*/
/**
* @param {ListNode} l1
* @param {ListNode} l2
* @return {ListNode}
*/
var mergeTwoLists = function (l1, l2) {
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
}

}``````

``````/**
* 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
}
}``````