This is still experimental and will most likely change later
Extended XForms has its own JavaScript code that provides the following functionalities:
Retrieve a model
Retrieve an instance
Retrieve a specific data node in an instance
Retrieve an attribute
Update a data node
Track a specific data node's changes.
Unfortunately, these rely heavily on the specific XSLTForms implementation and will not work with XSLTForms versions that use a different implementation, let alone other XForms frameworks.
Even though these functions can be used directly by the developer, they were implemented to be used by the JavaScript code from other Extended XForms stylesheets.