title: Uncaught TypeError: Cannot read property 'RecaptchaVerifier' of undefined at app.js:22,this is the error i am getting.in browser,please resolve it
body: <p>I am trying to implement Firebase Phone Number Authentication as described 
  Uncaught TypeError: Cannot read property 'RecaptchaVerifier' of undefined     at app.js:22
  please go through the code ,i am not able to figure out.and reply has soon as possible.</p>
  
  <p>app.js</p>
  
  <pre><code>
  // window.recaptchaVerifier = new firebase.auth.RecaptchaVerifier('sign-in-button', {
  //   'size': 'invisible',
  //   'callback': function(response) {
  //     // reCAPTCHA solved, allow signInWithPhoneNumber.
  //     onSignInSubmit();
  //   }
  // });
  //firebase.auth().languageCode = 'it';
  
  // var recaptchaResponse = grecaptcha.getResponse(window.recaptchaWidgetId);
  $('#verify_otp_model').hide()
  $('#errorbox').hide()
  
  // phone auth
    window.recaptchaVerifier = new firebase.auth.RecaptchaVerifier('getotp', {
      'size': 'invisible',
      'callback': function(response) {
        // reCAPTCHA solved, allow signInWithPhoneNumber.
        //onSignInSubmit();
  
      }
    });
    // [END appVerifier]
  
  recaptchaVerifier.render().then(function(widgetId) {
      window.recaptchaWidgetId = widgetId;
    //  updateSignInButtonUI();
    });
  
   );
  </code></pre>
  
  <p>app.html</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  
  
          &lt;!-- The core Firebase JS SDK is always required and must be listed first --&gt;
  &lt;script src="https://www.gstatic.com/firebasejs/7.14.3/firebase-app.js"&gt;&lt;/script&gt;
  
  &lt;!-- TODO: Add SDKs for Firebase products that you want to use
       https://firebase.google.com/docs/web/setup#available-libraries --&gt;
  
  &lt;script src="https://www.gstatic.com/firebasejs/7.14.3/firebase-analytics.js"&gt;&lt;/script&gt;
  
  &lt;script&gt;
    // Your web app's Firebase configuration
    var firebaseConfig = {
      apiKey: "AIzaSyDLFhLuJ_SOJDqLcJOi2-7tUhLrJ8wstZU",
      authDomain: "voting-6d410.firebaseapp.com",
      databaseURL: "https://voting-6d410.firebaseio.com",
      projectId: "voting-6d410",
      storageBucket: "voting-6d410.appspot.com",
      messagingSenderId: "769418906177",
      appId: "1:769418906177:web:852a15ba5e50033fd514c0",
      measurementId: "G-37YQP4X9WG"
    };
    // Initialize Firebase
    firebase.initializeApp(firebaseConfig);
    firebase.analytics();
  &lt;/script&gt;
      &lt;/head&gt;
      &lt;body class="gray-bg"&gt;
      &lt;/body&gt;
  
  
  &lt;/html&gt;
  </code></pre>