title: Cannot read property 'RecaptchaVerifier' of undefined
body: <p>I am trying to implement phone auth using firebase.
  I was going through this guide -&gt; <a href="https://fireship.io/lessons/firebase-phone-authentication-with-angular-4-tutorial/" rel="nofollow noreferrer">https://fireship.io/lessons/firebase-phone-authentication-with-angular-4-tutorial/</a></p>
  <pre><code>Cannot read property 'RecaptchaVerifier' of undefined&lt;
      at PhoneLoginComponent.ngOnInit (phone-login.component.ts:41)
      at callHook (core.js:2922)
      at callHooks (core.js:2892)
      at executeInitAndCheckHooks (core.js:2844)
      at refreshView (core.js:7213)
      at refreshEmbeddedViews (core.js:8289)
      at refreshView (core.js:7222)
      at refreshComponent (core.js:8335)
      at refreshChildComponents (core.js:6991)
      at refreshView (core.js:7248)
  </code></pre>
  <p>I keep getting the above error</p>
  <pre><code>import { auth } from 'firebase/app';
  
  ngOnInit(): void {
     this.windowRef = this.win.windowRef;
     this.windowRef.recaptchaVerifier = new  auth.RecaptchaVerifier('recaptcha-container');
     this.windowRef.recaptchaVerifier.render();
  }
  </code></pre>
  <p>I have already initialized firebase app in app.module.ts</p>
  <p>from package.json<br>
  &quot;firebase&quot;: &quot;^7.15.5&quot;<br>
  &quot;@angular/fire&quot;: &quot;^6.0.2&quot;,</p>