How to Check if a host object has been properly added?

[ahmed-salem-me]

A call from web-code on a method of an added host object works in one scenario but not the other.
So I'm looking for a way to check if the host object been properly added, even by just a console check..
here onCallBack is properly added and I receive the native call fine, xyz is just a dummy name yet, they both seem to give the same error or value when just typed in the console

In a different scenario, a method call on onCallBack fails with this error and I can't figure out why or even if the host object been added properly