app.js

controller: function($scope, $state) {
          $scope.fetchUser = function() {
            $scope.user = firebase.auth().currentUser;
            console.log("fetchUser() returns " + $scope.user);
          };
          $scope.isAuthenticated = function() {
            if (firebase.auth().currentUser) {
              return true;
            }
            return false;
          };

          $scope.deauth = function() {
            console.log('Deauth called');
            firebase.auth().signOut().then(function() {
              $state.go($state.current, {}, {reload: true});
            }, function(error) {
              // An error happened.
              console.log(error);
            });
          };
          $scope.fetchUser();
        }

main.html

<div class="col-lg-3 col-jnxn" id="jnxn-messaging">
      <div class="card" ng-show="isAuthenticated()">
        {{ user }}
        <hr>
        <button type="button" ng-click="deauth()" id="btn-join" class="btn btn-default btn-lg btn-block">Sign out</button>
      </div>
      <div class="card" ng-hide="isAuthenticated()">
        <div class="ad" id="junction-ad">
          <h4>Welcome to Junction!</h4>
          <p>
            {{ user }}
          </p>
        </div>
        <hr>
        <button type="submit" ui-sref="auth" id="btn-signin" class="btn btn-default btn-lg btn-block">Sign in</button>
        <button type="button" ui-sref="auth" id="btn-join" class="btn btn-default btn-lg btn-block">Join for free</button>
      </div>
    </div>