I need to allow read and write to my Firestore database for only users logged in anonymously.

This is the logic I am using

firebase.auth().signInAnonymously()
  .then(() => {
    // Signed in.
    console.log("we are signed in")

  })
  .catch((error) => {
    var errorCode = error.code;
    var errorMessage = error.message;
    // ...
  });

firebase.auth().onAuthStateChanged((user) => {
  if (user) {
    var uid = user.uid;
    console.log(user.uid + " User uid")
  } else {}
});

This is the rule I have setup but its not working.

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if request.auth.uid != null;
    }
  }
}