[{"data":[{"value":100,"fl":1},{"value":300,"fl":0},{"value":14,"fl":0},{"value":3,"fl":0},{"value":30,"fl":1},{"value":60,"fl":1}]}]

db.collection.aggregate([{"$set":{"data":{"$map":{"input":"$data","in":{"$mergeObjects":["$$m",{"f2":"$$m.fl"}]},"as":"m"}}}}])