Classificação do lado do servidor usando o Mongoose (mongodb + node.js)

var mongoose = require('mongoose');
mongoose.connect(uri);
mongoose.connection.on("open", function(err){
  mongoose.connection.db.eval("function(x){ return x; }", "asdf", function (err, retval) {
      console.log('err: '+err);
      console.log('retval: '+retval);
  });
});