Switch to BJS version 5 and your problem will be solved. It seems 4.2.1 really doesn’t have these methods. I did what I should do as the first. Created a project using 4.2.1 and it has only a Parse method and no getControlByName.
Or you can load the gui by fetching it from the server, pass it to the Parse method.
The getControlByName can be replaced by gui.getChildren().find(c => c.name === "name")
Sorry for being lame 