javascript - Find inside callback of another find (...), how to escape from callback hell? -

(first: i'm sorry, don't speak english well!)

i wanna return results of 3 finds in 1 array. code (next) running well, i'm in callback hell!

_schema   .static('retrieveall', function(cb) {     query = {};     this.find(query, function(err, data) {       if(err) {         cb(err, null);         return;       }        if(data)         = data;       else         = [];        _storesmodel.find(query).select('contact address').exec(function(err, data) {         if(err) {           cb(err, null);           return;         }          if(data) {           = data.reduce(function(coll, item) {             coll.push(item);             return coll;           }, all);         }          _customersmodel.find(query).select('contact address').exec(function(err, data) {           if(err) {             cb(err, null);             return;           }            if(data) {             = data.reduce(function(coll, item) {               coll.push(item);               return coll;             }, all);           }            cb(null, all);                   });       });     });   }); 

i've find inside find inside find. there anyway improve this?

solution:

_schema .static('retrieveall', function(cb) { var model = this;

_async.parallel(   { contacts: function(cb) {       model.find({}).exec(cb);     }   , stores: function(cb) {       _storesmodel.find({}).select('contact address').exec(cb);     }   , costumers: function(cb) {       _costumersmodel.find({}).select('contact address').exec(cb);     }   } , function(err, data) {   if(err) {     cb(err, null);     return   }    var ret = [];   if(data.contacts.length > 0) {     ret = ret.concat(data.contacts);   }   if(data.stores.length > 0) {     ret = ret.concat(data.stores);   }   if(data.costumers.length > 0) {     ret = ret.concat(data.costumers);   }    cb(null, ret); }); 

take @ npm async. great library of different patterns can used on node.js.

you want use waterfall if there chronological priority or parallel pattern if can execute in parallel.