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Could anyone help me with this code? I need to return a value form a routeToRoom function:

var sys = require('sys');

function routeToRoom(userId, passw) {
    var roomId = 0;
    var nStore = require('nstore/lib/nstore').extend(require('nstore/lib/nstore/query')());
    var users = nStore.new('data/users.db', function() {

        users.find({
            user: userId,
            pass: passw
        }, (function(err, results) {
            if (err) {
                roomId = -1;
            } else {
                roomId = results.creationix.room;
            }
        }
        ));
    });
    return roomId;
}
sys.puts(routeToRoom("alex", "123"));

But I get always: 0

I guess return roomId; is executed before roomId=results.creationix.room. Could someone help me with this code?

Could anyone help me with this code? I need to return a value form a routeToRoom function:

var sys = require('sys');

function routeToRoom(userId, passw) {
    var roomId = 0;
    var nStore = require('nstore/lib/nstore').extend(require('nstore/lib/nstore/query')());
    var users = nStore.new('data/users.db', function() {

        users.find({
            user: userId,
            pass: passw
        }, (function(err, results) {
            if (err) {
                roomId = -1;
            } else {
                roomId = results.creationix.room;
            }
        }
        ));
    });
    return roomId;
}
sys.puts(routeToRoom("alex", "123"));

But I get always: 0

I guess return roomId; is executed before roomId=results.creationix.room. Could someone help me with this code?

• javascript
• node.js
• asynchronous

Share Improve this question Follow edited Nov 9, 2018 at 20:30 hong4rc 4,10344 gold badges2323 silver badges4242 bronze badges asked Aug 31, 2011 at 10:57 profesoralexprofesoralex 41711 gold badge33 silver badges1010 bronze badges

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2 Answers 2

Sorted by: Reset to default 44

function routeToRoom(userId, passw, cb) {
    var roomId = 0;
    var nStore = require('nstore/lib/nstore').extend(require('nstore/lib/nstore/query')());
    var users = nStore.new('data/users.db', function() {
        users.find({
            user: userId,
            pass: passw
        }, function(err, results) {
            if (err) {
                roomId = -1;
            } else {
                roomId = results.creationix.room;
            }
            cb(roomId);
        });
    });
}
routeToRoom("alex", "123", function(id) {
    console.log(id);    
});

You need to use callbacks. That's how asynchronous IO works. Btw sys.puts is deprecated

You are trying to execute an asynchronous function in a synchronous way, which is unfortunately not possible in Javascript.

As you guessed correctly, the roomId=results.... is executed when the loading from the DB completes, which is done asynchronously, so AFTER the resto of your code is completed.

Look at this article, it talks about .insert and not .find, but the idea is the same : http://metaduck.com/01-asynchronous-iteration-patterns.html

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