function dataOr dataOr<T>(res: Response,fallback: T): Promise<T> Returns the payload of res, or fallback when the response says success: false. readFirstPage reads the profile pages' lists with it, and the profile its invitees, so that a list the server refuses shows empty rather than failing the page. Type Parameters T Parameters res: Response fallback: T Return Type Promise<T> Throws Error When the body isn't JSON or isn't an envelope.