text: mergeList(one, two) = () => {
      let oneCurr = one.head;
      let twoCurr = two.head;
      let one_next;
      let two_next;
  
      while (oneCurr != null && twoCurr != null) {
          let one_next = oneCurr.next;
          let two_next = twoCurr.next;
  
          twoCurr.next = one_next;
          oneCurr.next = twoCurr;
  
          oneCurr = one_next;
          twoCurr = two_next; 
      }
      oneCurr = one.head;
  }