unload
The unload module allows modules to register callbacks that are called
when they are unloaded.
API Reference
Functions
ensure(object, name)
Calling ensure() on an object does two things:
- It replaces a destructor method with a wrapper method that will never call the destructor more than once.
- It ensures that this wrapper method is called when the object's module is unloaded.
Therefore, when you register an object with ensure(), you can call its
destructor method yourself, you can let it happen for you, or you can do both.
The destructor will be called with a single argument describing the reason
for the unload; see when(). If object does not have the expected 
destructor method, then an exception is thrown when ensure() is called.
An object that defines a destructor method.
Optional name of the destructor method. Default is unload.
when(callback)
Registers a function to be called when the module is unloaded.
A function that will be called when the module is unloaded. It is called
with a single argument, one of the following strings describing the reason
for unload: "uninstall", "disable", "shutdown", "upgrade", or
"downgrade". If a reason could not be determined, undefined will be
passed instead.
Note that if an add-on is unloaded with reason "disable", it will not be
notified about "uninstall" while it is disabled. See
bug 571049.
