throw new DomEx(DomEx.NO_MODIFICATION_ALLOWED_ERR);
throw new DomDOMException(DOMException.NO_MODIFICATION_ALLOWED_ERR);
  public void appendData(String arg)  {    if (isReadonly())      {      throw new DomEx(DomEx.NO_MODIFICATION_ALLOWED_ERR);      }    String value = text + arg;    mutating(value);    text = value;  }