javascript app running in crhome with connection to postgreSQL

OK, I have to admit this is a case of my being influenced by things going on
in the news, which I am not normally influenced by.

All the news about the touch screens on the crew dragon capsule using a
JavaScript app running in Chrome, have me thinking about doing some
testing for a project I am working on that I am not happy with the
direction we are currently going in for the fronted. 

Can anyone point me to some documentation as to how to start building a
test application for this?

My first question is whether this would have a persistent connection to the
backend database, or would it work like a CGI script, and have to make a
connection to the backend every time the user takes an action?

-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                        -- Benjamin Franklin