A couple of problems with the API.

First, why do you have to call checkDestinationQueue after modifying the queue? It's awfully redundant. I assume this is due to some kind of limitation.

And second, goingUpIndicator and goingDownIndicator are kind of sketchy. Can you activate both at the same time? What effect would that have? There should be a single property, directionIndicator of an enum type with the possible values up, down, and none. I don't think you can make enums in javascript though, but I don't know the language very well. I'm just explaining this in terms that I know; there probably is a suitable javascript equivalent or replacement.