Node.js MongoDB HW#3.1

3.1

var MongoClient = require('mongodb').MongoClient;
 
MongoClient.connect('mongodb://localhost:27017/school', function(err, db) {
    if(err) throw err;
    
    db.collection('students').aggregate(
        {'$unwind':'$scores'},
        {'$match':{'scores.type': 'homework'}},
        {'$group':{'_id':'$_id', 
            // 'scores':{$addToSet:'$scores.score'}, 
            // 'type': {$addToSet:'$scores.type'}, 
            // 'name': {$addToSet: '$name'},
            'minScore': {$min: '$scores.score'}
        }},
        {'$sort': {'_id': 1}},
        function(err, doc) {
            // console.dir(doc);
            // console.dir(doc.length);
            for (var i = 0; i < doc.length; i++) {
                var id = doc[i]._id;
                var minScore = doc[i].minScore;
                // console.dir(id + " : " + minScore);
                db.collection('students').update(
                    {_id: id, 'scores.score': minScore},
                    {$pull: {scores: {'score': minScore}}},
                    function(err, updated) {
                        console.dir("Successfully updated " + updated + " document!");
                    }
                );
            }
        });
});