How to get the key from a Firebase data snapshot?

Question

I\'m able to query my users array with an e-mail address and return the user\'s account info:

users.orderByChild(\'email\').equalTo(authData.user.em         


        

Answer 1

users.orderByChild('email').equalTo(authData.user.email) is a Query (doc) that you have built by "chaining together one or more of the filter methods". What is a bit specific with your query is that it returns a dataSnapshot with only one child, since you query with equalTo(authData.user.email).

As explained here, in this exact case, you should loop over the returned dataSnapshot with forEach():

Attaching a value observer to a list of data will return the entire list of data as a single snapshot which you can then loop over to access individual children.

Even when there is only a single match for the query, the snapshot is still a list; it just contains a single item. To access the item, you need to loop over the result, as follows:

ref.once('value', function(snapshot) {
  snapshot.forEach(function(childSnapshot) {
    var childKey = childSnapshot.key;
    var childData = childSnapshot.val();
    // ...
  });
});