Is it possible to program extensions using Javascript only and integrate with SAP HANA system later?
Can I use API to get information from the DB, manipulate them and possibly save them to DB or external DB which will be accessed later as well?
Thank you and I am sorry but I could not find it on SAP pages.
If I understood your question correctly, this is exactly what XSJS Can do for you. Proven and tested. Another option would be oData which is more convenient way in case you do not need some advanced logic.