description to merging sorted linked lists

merge sorted linked lists

var mergeTwoLists = function(l1, l2) {
    const newNode = new ListNode(-1);
    
    function mergeTwoListsRec(newL1Head, newL2Head, prevHead) {
        
        if(!newL1Head || !newL2Head) {
            prevHead.next = (newL1Head || newL2Head);
            return;
        }
        
        const newHead = (newL1Head.val <= newL2Head.val) ? newL1Head : newL2Head;
        
         prevHead.next = newHead;
        
        if(newHead === newL1Head) newL1Head = newL1Head.next;
        
        if(newHead === newL2Head) newL2Head = newL2Head.next;
        
        mergeTwoListsRec(newL1Head, newL2Head, newHead);
    }
    
    mergeTwoListsRec(l1, l2, newNode);
    
    return newNode.next;
};