[{"empno":1500,"province":"North"},{"empno":1600,"province":"West"}]

db.collection.aggregate([{"$facet":{"g0":[{"$match":{"province":{"$eq":"North"}}},{"$group":{"_id":null,"count":{"$sum":1}}},{"$project":{"_id":0}}],"g1":[{"$match":{"province":{"$eq":"East"}}},{"$group":{"_id":null,"count":{"$sum":1}}},{"$project":{"_id":0}}],"g2":[{"$match":{"province":{"$eq":"South"}}},{"$group":{"_id":null,"count":{"$sum":1}}},{"$project":{"_id":0}}],"g3":[{"$match":{"province":{"$eq":"West"}}},{"$group":{"_id":null,"count":{"$sum":1}}},{"$project":{"_id":0}}]}},{"$set":{"data":{"$map":{"input":{"$objectToArray":"$$ROOT"},"in":{"$cond":[{"$eq":["$$d.v",[]]},0,{"$let":{"vars":{"m":{"$arrayElemAt":["$$d.v",0]}},"in":"$$m.count"}}]},"as":"d"}}}},{"$project":{"data":1}}])