You can't
The explanation is here [How do I return a list of users if I use the Firebase simple username & password authentication](https://stackoverflow.com/questions/14673708/how-do-i-return-a-list-of-users-if-i-use-the-firebase-simple-username-password)
You can instead set the user's uid to users node in your database, I use that node to store other user's information. then you can get the number of children under that node.

You can't
The explanation is here [https://stackoverflow.com/questions/14673708/how-do-i-return-a-list-of-users-if-i-use-the-firebase-simple-username-password][1]
You can instead set the user's uid to `users` node in your database, I use that node to store other user's information. then you can get the number of childs under that node.

[1]: https://stackoverflow.com/questions/14673708/how-do-i-return-a-list-of-users-if-i-use-the-firebase-simple-username-password