merge two sorted link-list JS

21. Merge Two Sorted Lists
    You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by
splicing together the nodes of the first two lists.

Return the head of the merged linked list.

https://leetcode.com/problems/merge-two-sorted-lists/description/

I am trying to solve this problem and i don’t understand why my logic or code is wrong !!

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {
    let head = new ListNode()
    let temp = head
    while(list1 && list2){
        if(list1.val>list2.val){
            head.next = list2
            list2 = list2.next
        }
        if(list1.val <= list2.val){
            head.next = list1
            list1 = list1.next
        }
        head = head.next
    }
    if(list1){
        head.next = list1
    }
    if(list2){
        head.next = list2
    }
    return temp.next
};

My test case is this:

Thank you