Question

NodeJS + Express, MongoDB + Mongoose

I have a JSON feed where each record has a set of “venue” attributes (things like “venue name” “venue location” “venue phone” etc). I want to create a collection of all venues in the feed — one instance of each venue, no dupes.

I loop through the JSON and test whether the venue exists in my venue collection. If it doesn’t, save it.

jsonObj.events.forEach(function(element, index, array){
    Venue.findOne({'name': element.vname}, function(err,doc){
        if(doc == null){
            var instance = new Venue();
            instance.name = element.vname;
            instance.location = element.location;
            instance.phone = element.vphone;
            instance.save();
        }
    }
}

Desired: A list of all venues (no dupes).

Result: Plenty of dupes in the venue collection.

Basically, the loop created a new Venue record for every record in the JSON feed.

I’m learning Node and its async qualities, so I believe the for loop finishes before even the first save() function finishes — so the if statement is always checking against an empty collection. Console.logging backs this claim up.

I’m not sure how to rework this so that it performs the desired task. I’ve tried caolan’s async module but I can’t get it to help. There’s a good chance I’m using incorrectly.

Thanks so much for pointing me in the right direction — I’ve searched to no avail. If the async module is the right answer, I’d love your help with how to implement it in this specific case.

Thanks again!

Answer 1

Why not go the other way with it? You didn’t say what your persistence layer is, but it looks like mongoose or possibly FastLegS. In either case, you can create a Unique Index on your Name field. Then, you can just try to save anything, and handle the error if it’s a unique index violation.