Javascript scope not updating global variable

Question

I'm sitting in my js file trying to upload but for some reason, I don't understand entirely. My :: myUid isn't updating. Can anyone tell me how to fix it and maybe even why it's the case that myUid isn't updating?

var myUid = '33';

firebase.auth().signInAnonymously().catch(function(error) {
    // Handle Errors here.
    var errorCode = error.code;
    var errorMessage = error.message;
    // ...
  });

firebase.auth().onAuthStateChanged(function(user) {
    if (user) {
        // User is signed in.
        var isAnonymous = user.isAnonymous;
        window.myUid = user.uid;
        // ...
    } else {
        // User is signed out.
        // ...
    }
    // ...
});


function writeUserData() {
    database.ref('users/').set({
    profileID: myUid,
  });
};

writeUserData();

Best regards, Sam

Answer 1

myUid value is updated only when the callback for onAuthStateChanged is executed asynchronously . By the time you invoke the writeUserData() function on your main execution flow, the above callback may not be have been completed yet.

So a better approach would be to get rid of the global variable and invoke the writeUserData function from the onAuthStateChanged callback, passing the user uid as a parameter.

function writeUserData(userUid) {
    database.ref('users/').set({
    profileID: userUid,
  });
};

firebase.auth().onAuthStateChanged(function(user) {
    if (user) {
        // User is signed in.
        var isAnonymous = user.isAnonymous;
        writeUserData(user.uid);
        // ...
    } else {
        // User is signed out.
        // ...
    }
    // ...
});