javascript - How to handle results of multiple async callbacks in Node -

i'm working on scenario in node involves multiple async.map calls, 1 of nested in _.map function need access nested arrays. i'm struggling combine results of these calls array return in end.

more specifics on scenario:

i start userid , query games db find games userid associated with. pull gameid , description each game.

i query gameid of each of these games find userids associated each game. filter original userid out of these results.

next query users db each of these userids in order details such user email , name. (note: _.map comes play userids nested in array of arrays; each inner array representing game).

the last step, , i'm struggling, how combine these results , return them. final desired array looks below. array of game objects. each game object has gameid, description, , users property. users array of users associated game , has id, email, , name properties.

[   {     gameid: 'dfh48643hdgf',     description: 'lorem ipsum...',     users: [       {         id: 1,         email: 'test@example.com',         name: 'john doe'       },       {         id: 7,         email: 'sample@example.com',         name: 'jane smith'       }, ...     ]   }, ... ] 

below code have (note: code block part of larger async.series call):

sharedgames: function(next) {   db.games.index({userid: userid},     function(err, gamesdata) {       if (err) {         logger.warn('error retrieving games userid %d', userid, err);         next(err, null);       } else {         gamesdata = _.map(gamesdata, function(game) {           return {             gameid: game.id,             description: game.description,             users: []           };         });         async.map(gamesdata,           function(item, callback) {             db.gamedetails.getgameusers({gameid: item.gameid},               function(err, users) {                 if (err) {                   callback(err, null);                 } else {                   callback(null, _.without(users.userids, number(userid)));                 }               }             );           },           function(err, results) {             if (err) {               next(null, null);             } else {               var flattenedresults = _.chain(results)                 .flatten()                 .uniq()                 .value();               async.map(flattenedresults, function(user, callback) {                 db.users.getbyid(user, function(err, userdetails) {                   if (err) {                     callback(err, null);                   } else {                     callback(null, _.pick(userdetails, 'id', 'email', 'name'));                   }                 });               }, function(err, users) {                 if (err) {                   next(null, null);                 } else {                   _.each(results, function(result, index) {                     _.each(result, function(user) {                       var customerdetails = _.find(customers, function(u) {                         return u.id === user;                       });                       gamesdata[index].users.push(userdetails);                     });                   });                   console.log(gamesdata);                   next(null, gamesdata);                 }               });             }           }         );         next(null, []);       }     }   ); } 

so can accomplish you're describing async.auto. check docs:

async.auto({ get_data: function(callback){     console.log('in get_data');     // async code data     callback(null, 'data', 'converted array'); }, make_folder: function(callback){     console.log('in make_folder');     // async code create directory store file in     // run @ same time getting data     callback(null, 'folder'); }, write_file: ['get_data', 'make_folder', function(callback, results){     console.log('in write_file', json.stringify(results));     // once there data , directory exists,     // write data file in directory     callback(null, 'filename'); }], email_link: ['write_file', function(callback, results){     console.log('in email_link', json.stringify(results));     // once file written let's email link it...     // results.write_file contains filename returned write_file.     callback(null, {'file':results.write_file, 'email':'user@example.com'}); }] }, function(err, results) {     console.log('err = ', err);     console.log('results = ', results); }); 

so if follow same approach, can array of game objects injecting more info every call. can use async.waterfall. hope helps