Cara mendapatkan data Mongo menggunakan agregat MongoDB versi 3.0

Coba codeRefer berikut - https://docs.mongodb.com/manual /reference/operator/aggregation/eq/

https://docs.mongodb.com/manual/reference/operator/ agregasi/kond/

https://docs.mongodb.com/manual/reference/operator/ agregasi/grup/

DB.aggregate([
                {$project:
                {
                    tag_id: '$tag_id',
                    unreadcount: { $cond: [ { $eq: [ '$unread', 'true' ] }, 1, 0 ] }
                }},
                { $group: {
                    _id: '$tag_id',
                    unread: { $sum: '$unreadcount'},
                }}
            ], function (err, results) {
                console.log(results);
            })