Code snippet 4 for blog post http://blog.geomusings.com/2014/02/18/a-little-deeper-with-node-and-postgis/

snippet4.js

/roll up the results
query.on('row', function (result) {
  if (!result) {
      return res.send('No data found');
  } else {
      if (geom == "features") {
          coll.features.push(geojson.getFeatureResult(result, spatialcol)); //use helper function
      } else if (geom == "geometry") {
          var shape = JSON.parse(result.geojson);
          coll.geometries.push(shape);
      }
  }
});

//send the results
query.on('end', function (err, result) {
  res.setHeader('Content-Type', 'application/json');
  res.send(coll);
});