MongoJS synchronous call

Question

I'm fixing some bugs in one project. I need synchronous cursor, to load data in loop. I have code:

var mongo     = require('mongojs'),
    dataMaps  = [];

mongo.penguin_friends.find({ user_id_1: id_user }, function(err, friends) {     
    friends.forEach(function(data) {
        var cursor = mongo.penguin_user_maps3.find({ user_id: data.id_user }, { fields: { maps: 1 } });
    //I need to do dataMaps.push(cursor.data);

    });

    console.log("processingThisSomething()");

    processSomething();     
});

I need to complete this request before calling processSomething(); So I need to process mongodb query inside a loop synchronously.

It's not possible to make the queries synchronous. The API doesn't support it. But, you can use an iterator that supports asynchronous blocks. E.g., async.each(). — Jonathan Lonowski
– Jonathan Lonowski, Commented May 8, 2014 at 15:02

Jonathan Lonowski · Accepted Answer · 2014-05-08 15:50:37Z

It's not possible to make the queries synchronous as the API doesn't support it.

You'll have to provide a callback to .find() or a cursor method to receive the results:

cursor.toArray(function (err, maps) {
    if (!err) {
        dataMaps.push(maps);
    }
});

But, you can replace the iterator with one that's asynchronous-aware, such as async.each(), to continue when they've completed:

async.each(
    friends,

    function (data, callback) {
        var cursor = mongo....;

        cursor.toArray(function (err, maps) {
            if (!err) {
                dataMaps.push(maps);
            }

            callback(err);
        });
    },

    function (err) {
        if (!err) {
            processSomething();
        }
    }
);

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