title: core.js:4197 ERROR TypeError: Cannot read property 'TwitterAuthProvider' of undefined
body: <pre><code>   var provider = new firebase.auth.TwitterAuthProvider();
    firebase.auth().signInWithPopup(provider).then(function(result) {
      // This gives you a the Twitter OAuth 1.0 Access Token and Secret.
      // You can use these server side with your app's credentials to access the Twitter API.
      // var token = result.credential.accessToken;
      // var secret = result.credential.secret;
      // The signed-in user info.
      var user = result.user;
      console.log(user);
      // ...
    }).catch(function(error) {
      // Handle Errors here.
      var errorCode = error.code;
      var errorMessage = error.message;
      // The email of the user's account used.
      var email = error.email;
      // The firebase.auth.AuthCredential type that was used.
      var credential = error.credential;
      // ...
    });
  </code></pre>
  <p>I am getting
  <strong>core.js:4197 ERROR TypeError: Cannot read property 'TwitterAuthProvider' of undefined</strong>
  error while running the application</p>