title: Firebase stop listening onAuthStateChanged
body: <p>As of version ^3.0.0, I'm having a difficult time removing the auth state change listener. </p>
  
  <p>To start the listener per the documentation: </p>
  
  <pre><code>firebase.auth().onAuthStateChanged(function (user) {
      // handle it
  });
  </code></pre>
  
  <p>However, I cannot find anywhere in the documentation that refers to a remove auth state change listener. There is peculiar function on the Firebase.Auth class called <code>removeAuthTokenListener</code>. Unfortunately it's not documented (<a href="https://firebase.google.com/docs/reference/js/index-all" rel="noreferrer">firebase docs reference</a>). </p>
  
  <p>Via your browser's web console. </p>
  
  <pre><code>var auth = firebase.auth();
  auth.removeAuthTokenListener;
  </code></pre>
  
  <p>prints a function definition that takes one parameter. I tried to do the following:</p>
  
  <pre><code>this.authListener = firebase.auth().onAuthStateChanged(function (user) {...});
  firebase.auth().removeAuthTokenListener(this.authListener);
  </code></pre>
  
  <p>but that didn't do anything. </p>