Firebase: Detecting if data exists. This snippet detects if a user ID is already taken

firebase_detect_data.js

function go() {
  var userId = prompt('Username?', 'Guest');
  checkIfUserExists(userId);
}

var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users';

function userExistsCallback(userId, exists) {
  if (exists) {
    alert('user ' + userId + ' exists!');
  } else {
    alert('user ' + userId + ' does not exist!');
  }
}

// Tests to see if /users/<userId> has any data. 
function checkIfUserExists(userId) {
  var usersRef = new Firebase(USERS_LOCATION);
  usersRef.child(userId).once('value', function(snapshot) {
    var exists = (snapshot.val() !== null);
    userExistsCallback(userId, exists);
  });
}

The crux: var exists = (snapshot.val() !== null);

if you want to listen on a node. You can change the implementation to the snippet below.

  const checkIfUserExists = (userId) => {
    const usersRef = new Firebase(USERS_LOCATION);
    usersRef.child(userId).on('value', (snap) => {
    const exists = (snap.val() !== null);
    userExistsCallback(userId, exists);
   });
 }

didn't know about the once() method. thanks 👍

Can you do this in swift?

Nice!

+2

I am making chat application using java, "https://github.com/Abdul007Malik/Conversa.git", I am confused and cannot progress further help me if you can, my questions:

1. if I know the auth.getUID of others can i modify there data or firebase have different mechanism to check authentication.
2. how can I send the invitation(inviting to join the group) to friends if i know there phone numbers but dont know there particular userid.

Did you find any solution for this. I am facing same issue where I know email id but not user id

Can you give us python examples??

Can you give us python examples??

For python example
https://stackoverflow.com/questions/59253867/how-to-check-if-a-child-in-firebase-database-exists-using-django/60844998#60844998

thank's man, very helpful =)