node.js - How to synchronize requests? -

i using nodejs+express+mongoose. assuming have 2 schemas , models in place: "fruits" , "vegetables".

assuming have following:

var testlist = ["tomato", "carrot", "orange"]; var convertedlist = []; // assume res "response" object in express 

i wan able check each item in array against "fruits" , "vegetables" collections respectively , insert them converted list tomato, carrot, , broccoli replaced respective documents.

below have pseudocode of think be, know not how this.

for(var = 0; < testlist.length; i++) { var fruitfind = fruit.find({"name":testlist[i]}); var vegfind = vegetables.find({"name":testlist[i]});  // if fruit if(fruitfind) { convertedlist.push(fruitfindresults); }  // if vegetable else if(vegfind) {  convertedlist.push(vegfindresults); }  // if identified fruit , vegetable (assume tomato doc listed under both fruit , vegetable collections) else if (fruitfind && vegfind) { convertedlist.push(vegfindresults); } }  // converted list should contain appropriate docs found. res.send(convertedlist) // appears return empty array... how deal waiting callbacks finish fruitfind , vegfinds? 

what best way this? or possible?

assuming there's 1 of each fruit/vegetable , intended push veggie that's found in both collections twice.

var async = require("async"),     testlist = ["tomato", "carrot", "orange"];  async.map(testlist, function (plant, next) {   async.parallel([function (done) {     fruit.findone({"name": plant}, done);   },   function (done) {     vegetables.findone({"name": plant}, done);   }], function (err, plants) { // edited: before (err, fruit, veggie) wrong     next(err, plants);   }); }, function (err, result) {   var convertedlist = [].concat(result);   res.send(convertedlist); }); 

note: haven't tested code, should work. the async module excellent managing callbacks btw.

update

to each fruit once, async.parallel callback have rewritten this:

function (err, plants) {   next(err, plants[0] || plants[1]); } 

and there's no concat needed anymore in .map callback:

function (err, result) {   res.send(result); }