Handling callback functions

Question

Handling callback functions

I am working on a node.js project in which I need to communicate with a mongoDb database. I am currently programming a function to find some data in my db using th node-mongodb-native module. Everything works, but my code looks like a callback in a callback in a callback in a callback...

I created this function to prevent me from using callbacks every time I want to access my database. I now just need to call this function.

module.exports.find = function(query, projection, callback){
    db.open(function(err, db){
        if(err) throw err;
        db.collection('rooms', function(err, collection){
            if(err) throw err;
            collection.find(query, projection, function(err, cursor){
                if (err) throw err;
                cursor.toArray(function(err, find){
                    db.close();
                    callback(err, find);
                });
            });
        });
    });
};

Is there a method to reduce this codeception ?
Thank you :)
I am sorry if my English is not really good, I am learning it.

javascript
node.js
asynchronous
callback

Answer 1

If you just want to know how to cleanup callbacks reasonably and scope db:

module.exports.find = function(query, projection, callback){
    var local_db;

    function db_open(err, db) {
        if(err) throw err;
        local_db = db;
        local_db.collection('rooms', handle_homes_collection);

    }

    function handle_homes_collection(err, collection){
        if(err) throw err;
        collection.find(query, projection, handle_find_query);
    }

    function handle_find_query(err, cursor){
        if (err) throw err;
        cursor.toArray(function(err, find){
            local_db.close();
            callback(err, find);
        });
    }

    db.open(db_open);
};

Answer 2

Like this:

module.exports.find = function(query, projection, callback){
    var database;

    db.open(function(err, db_temp){
        if(err) throw err;

        database = db_temp;
    });

    database.collection('rooms', function(err, collection){
        if(err) throw err;
        collection.find(query, projection, function(err, cursor){
            if (err) throw err;
            cursor.toArray(function(err, find){
                db.close();
                callback(err, find);
            });
        });
    });
};