[{"_id":123,"userName":"foo","profiles":[{"profileId":345,"hash":{"$binary":{"base64":"z7ynKE45RhOWvPkgtcN+Fg==","subType":"04"}}},{"profileId":456,"hash":{"$binary":{"base64":"z7ynKE45RhOWvPkgtcN+Fg==","subType":"04"}}}]}]

db.collection.aggregate([{$project:{userName:1,profiles:{$map:{input:"$profiles",in:{"$function":{"body":"function convert(s){let t=s.hex();var r=t.substr(6,2)+t.substr(4,2)+t.substr(2,2)+t.substr(0,2),u=t.substr(10,2)+t.substr(8,2),b=t.substr(14,2)+t.substr(12,2),e=t.substr(16,16);return t=r+u+b+e,t.substr(0,8)+'-'+t.substr(8,4)+'-'+t.substr(12,4)+'-'+t.substr(16,4)+'-'+t.substr(20,12)}","args":["$$this.hash"],"lang":"js"}}/**in: "$$this.hash"*/}}}}])