snippent.js

 function(eventList, next) {                                                                                                                                                           
                if (_.isEmpty(eventList))                                                                                                                                                         
                    return next(null, eventList);                                                                                                                                                 

                var tmp = {};                                                                                                                                                                     
                var val = _                                                                                                                                                                       
                    .chain(eventList)                                                                                                                                                             
                    .map(function(e) {

                        if(!e.patientId)                                                                                                                                                          
                            return e;                                                                                                                                                             

                        function patientInfo(pid, fn) {                                                                                                                                           
                            patients.read(pid, function(err, res) {
                                if(err)
                                    return fn(err);                                                                                                                                               
                                return fn(res);
                            });
                        }

                        patientInfo(e.patientId, function(res) {
                            e.patientInfo = res;
                            return e;
                        });
                    }).value()
 }