Database
[{"id":1,"foo":"ABC","moo":{a:1},"date":ISODate("2016-01-11T14:26:20.768Z"),"flag":false,"tags":[{"created":"2019-05-05",}]}]
Query
db.collection.aggregate([{$project:{types:{$map:{input:{$objectToArray:"$$CURRENT"},in:{$type:["$$this.v"]}}}}}])