What functions are supported by the CouchDB javascript engine

I want to do validate_doc_update

. What features are supported by this feature using CouchDB? Can I use the Array.find

, Array.map

, Object.keys

and other functions, such as these? If the latest version supports the features that the CouchDB version needs to be tuned to to make sure my check will work without crashing on every system, I would fetch the CouchDB version and make it higher than the specified version.