code: private static void deleteElem(Scriptable target, long index) {
          int i = (int)index;
          if (i == index) { target.delete(i); }
          else { target.delete(Long.toString(index)); }
      }
docs: /* Utility functions to encapsulate index > Integer.MAX_VALUE
  handling.  Also avoids unnecessary object creation that would
  be necessary to use the general ScriptRuntime.get/setElem
  functions... though this is probably premature optimization.