{ head: ok}?

I was looking at the advanced rails recipe for the errata. It has
format.js { hedda: ok}. does this not send back a full response so
you do not require an RJS file?

Also I see that the application helper has the remote_function in it.
Is this a better way to do a remote_function than putting it in the
view along with the ajax call? Does this circumvent the RJS call or
does the { head: ok } do that?