docs: public void setExternalArrayData(ExternalArrayData array)
      {
          externalData = array;
  
          if (array == null) {
              delete("length");
          } else {
              // Define "length" to return whatever length the List gives us.
              defineProperty("length", null,
                             GET_ARRAY_LENGTH, null, READONLY | DONTENUM);
          }
      }