Shaping data from PG/Node query?

I am having trouble understanding how to shape my queried data into a specific json structure. For example how could I do something like the following? (this is not real code just what I would like to accomplish). Thank you!

router.get('/data/:start/:end', function(req, res, next) {

    pg.defaults.ssl = true;
    pg.connect('dburl', function(err, client, done) {

        if (err) throw err;
        console.log('db connected');

            client.query("SELECT * FROM tablename WHERE datetime::date >= '"+req.params.startdate +"'::date AND datetime::date <= '"+req.params.enddate +"'::date ", function(err, rows, fields) {

                //HERE CAN I ITERATE THROUGH THE ROW RESULTS?
                for (var i = 0; i < rows.length; i++) {

                        //AND SHAPE A NEW STRUCTURE?
                        console.log(rows[i].lat);
                        res.json({ latitude: rows[i].lat, longitude: rows[i].long,});

                }

                res.send('hi');

                done();

            });

    });


});

via andehlu