Listen only to additions to a cloud firestore collection?

Question

I\'ve noticed, when I try to use a realtime listener on a Collection in firestore, each time a new Document is added to the collection, the logic will be rerun, and I will d

Answer 1

It seems that the onSnapshotis only for listening an entire document,which means it would return all of the fields in a document that you're listening. So you are not able to only retrieve the changed field. But you can do different things according to different types of change:

xxxx.onSnapshot(function(querySnapshot){
     querySnapshot.docChanges.forEach(function(change){
                    if(change.type=="added"){//first time it will be triggered

                    }else if(change.type == "modified"){//modified

                    }else if(change.type == "removed"){//removed


                    }
    })
})

Hope this helps