Referencing Firebase Database With A Variable And String Concatenation

As you can see below i'm trying to read a list of data from the database and then loop over the result, in javascript. The function runs whenever i open/refresh the page: firebase.

Solution 1:

It is extremely unlikely that the problem is in the string concatenation itself. It is much more likely that uid simple doesn't have a value yet when you start reading from the database.

To make sure the uid is available, put the reading of the data into the auth state listener like this:

firebase.auth().onAuthStateChanged(function(user) {
  if (user) {
    uid = user.uid;
    console.log("uid="+uid);
    firebase.database().ref("Users/" + uid + "/rooms").on("value", function(snapshot) {
      snapshot.forEach(function(e) {
        var element = e.val();
        var roomId = element.Id;
        console.log("roodId="+roomId);
      });
    });
  }
})