Database
[{_id:"5dde4c55c6c36b3bb4f5ad30",name:"Peter",age:45,division:"marketing"}]
Query
db.collection.aggregate([{$replaceWith:{$arrayToObject:{$reduce:{input:{$objectToArray:"$$ROOT"},initialValue:[],in:{$concatArrays:["$$value",{$cond:[{$eq:[{$type:"$$this.v"},"string"]},["$$this"],[]]}]}}}}}])