LeetCode - 21 - Merge Two Sorted Lists

 /**

 * 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) {
    var mergedList = new ListNode(null, null);
    var pointer1 = list1, pointer2 = list2, pointer3 = mergedList;
    while (pointer1 !== null && pointer2 !== null) {
        var value;
        if (pointer1.val < pointer2.val) {
            value = pointer1.val;
            pointer1 = pointer1.next;
        } else {
            value = pointer2.val;
            pointer2 = pointer2.next;
        }
        pointer3.next = new ListNode(value, null);
        pointer3 = pointer3.next;
    }
    while (pointer1 !== null) {
        pointer3.next = new ListNode(pointer1.val, null);
        pointer3 = pointer3.next;
        pointer1 = pointer1.next;
    }
    while (pointer2 !== null) {
        pointer3.next = new ListNode(pointer2.val, null);
        pointer3 = pointer3.next;
        pointer2 = pointer2.next;
    }
    return mergedList.next;
};