How to use aggregation function mongo db-query

Question

I am new in MongoDB and I would like to use the aggregation function where I want to check type == topic and get the following output

E

Answer 1

To see the result of your aggregation you have to pass the callback to be executed as parameter.

records.PedagogyVersions.aggregate([
        {
            $match:{_id:latestVersion} // Step 4
        },
        {
           $unwind:"$contentNodes.LearningNodes"
        },
        {
            $group:
            {
                _id:"$contentNodes.LearningNodes",
                count:{$sum:1}
            }
        }
    ], function(err, results) {
         console.log(results);
    });