docs: public static Object setObjectElem(Object obj, Object elem, Object value,
                                         Context cx, Scriptable scope)
      {
          Scriptable sobj = toObjectOrNull(cx, obj, scope);
          if (sobj == null) {
              throw undefWriteError(obj, elem, value);
          }
          return setObjectElem(sobj, elem, value, cx);
      }