javascript - NodeJS + MongoDB ASYNC results appearing late -

i have simple function returns list of connected users in channel, using in initial stage simple array, know, want retrieve user details mongodb database , add array.

the problem i'm having return giving empty result, can see later on in console log because queries running late , return running before having results back.

i know because asynchronous functions, i've tried q , others cant working. :(

//get users specified room function get_room_users( room ){      // create array hold usernames of poeple in specific room     var roomusers = new array();              // clients in ‘room1′     var clients = io.sockets.clients( room );      var = 0;      for(var = 0; < clients.length; i++) {          db.users.findone( { email: clients[i].username }, function(err, userdata) {              if( err || ! userdata ){                  console.log('no user found');              } else {                  console.log("displaying user data: " + userdata.nickname);                 roomusers[roomusers.length] = userdata.nickname;                   console.log("here console shows roomusers filled in");                 console.log(roomusers);                  i++;              }          });      }      console.log("here array looks empty before sending back");     console.log(roomusers);      return roomusers;   }  var users = get_room_users(room1);  console.log("here array looks empty!") console.log(users); 

console log result

here array looks empty before sending [] here array looks empty! [] here console shows roomusers filled in ['user@user.com'] 

finally resolved: ok, 1 of users commented thinking in synchronous mode, changed emit method after bucle got resolved in order emit when has been done. keep in mind i'm using q create promisses :)

//get users specified room function get_room_users( room ){

var the_promises = [];  // create array hold usernames of poeple in specific room var roomusers = new array();          // clients in ‘room1′ var clients = io.sockets.clients( room );  clients.foreach(function (socket) {      var deferred = q.defer();      db.usuarios.findone( { email: socket.username }, function(err, userdata) {          if( err || ! userdata ){              console.log('no user found');             deferred.reject();          } else {              console.log("displaying user data: " + socket.username);             roomusers[roomusers.length] = socket.username;              console.log("dentro del bucle");             console.log(roomusers);              deferred.resolve();          }      });      the_promises.push(deferred.promise);       });   q.all(the_promises).done( function(){        console.log("all things done!");      // broadcast in room 1 usernames of clients connected.     io.sockets.to( room ).emit('updateroomusers', roomusers);     } ); 

}

i suggest use q promises (https://npmjs.org/package/q). promises powerfull tool scheduling asynchronous operations.