Mongo/Mongoose check if an item exists

Question

I'm pretty new to building large-scale web applications with Mongo and Mongoose and I'm wondering what the correct way to check if an items exists is.

I've commented the function below so it should be easy to understand what I'm doing and the wall I've hit. So essentially what I'm creating is: item_exists ? do nothing : save. I've currently removed the 'save' function as I'm not too sure where it should be placed.

app.post('/tracks/add/new', function (req, res) {

        var newTrack;

        // loop through the objects in req.body
        // item_exists ? do nothing : save

        for (var i = 0; i < req.body.length; i++) {

            newTrack = new tracksTable({
                for_user: req.user._id,
                title: req.body[i].title,
                artist: req.body[i].artist,
                artwork: req.body[i].artwork,
                source: req.body[i].source,
                stream: req.body[i].stream
            });

            // check if the item already exists by
            // first finding the 'for_user' field and
            // any tracks associated with it (title)

            var query = tracksTable.find({});

            query
                .where('for_user', req.user._id)
                .select('title')
                .exec(function (err, data) {
                    for (var x = 0; x < data.length; x++) {

                        // this is where I've hit a wall...
                        // does 'this' track in the database match
                        // one in the request?

                    }
                });

        }

    });

Solution

If you were looking for one item in the tracksTable collection you could do something like this:

tracksTable.findOne({for_user: req.user._id}, function(err, tracksTableItem) {
    if (err) {
        console.log("MongoDB Error: " + err);
        return false; // or callback
    }
    if (!tracksTableItem) {
        console.log("No item found, creating tracksTable item");

        tracksTable.create(
            {
                for_user: req.user._id,
                title: req.body[i].title,
                artist: req.body[i].artist,
                artwork: req.body[i].artwork,
                source: req.body[i].source,
                stream: req.body[i].stream
            }, function(err, createdItem) {
                if (err) {
                    console.log("MongoDB Error: " + err);
                    return null; // or callback
                }
            }
        );
    }
    else {
        console.log("Found one tracksTable item: " + tracksTableItem.for_user);
        // here you could even update your existing item using "tracksTable.save"
    }
    return true; // or callback
}

Comments

[leaksterrr]

for_user is my relational field and one that I'm also using as a unique identifier for the lookups. I need to look for a 'for_user' item and see if it has a 'title' that matches one in the request. If not then save it to the tracks db.

[Santiag00]

I guess you could either add the req.body[i].title to the findOne condition or loop through the "tracksTableItem" tracks if a track item was found using the "for_user" field

[leaksterrr]

It's going to have to be the latter because the track could exist for another user but I'm doing two pretty big loops now (req loop and db loop)... Surely there's got to be a cleaner way?

[Santiag00]

Hmm unless I'm missing something and assuming the title is a simple String field I don't see why you can't do "findOne({for_user: req.user._id, title: req.body[i].title})" to look just for those tracks that belong to a certain user and have a certain title.