I am facing problem with initializing the **Firebase** and **Flutter** project, while I just updated my `firebase-tools` and `firebase` to **version 9** which is **modern web modular style** and its been a week nothing has helped the documentation of flutter is still according to version 8 which is old style compat type and when I follow firebase documentation which is updated its throwing errors with flutter. I need your help firebase and flutter experts please provide some solution.

The two error which I get are,

```
core.dart:56 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'app')
    at Object.app$ [as app] (core.dart:56)
    at initializeApp (firebase_core_web.dart:68)
    at initializeApp.next (<anonymous>)
    at runBody (async_patch.dart:84)
    at Object._async [as async] (async_patch.dart:123)
    at firebase_core_web.FirebaseCoreWeb.new.initializeApp (firebase_core_web.dart:28)
    at initializeApp (firebase.dart:42)
    at initializeApp.next (<anonymous>)
    at runBody (async_patch.dart:84)
    at Object._async [as async] (async_patch.dart:123)
    at Function.initializeApp (firebase.dart:38)
    at main$ (main.dart:9)
    at main$.next (<anonymous>)
    at runBody (async_patch.dart:84)
    at Object._async [as async] (async_patch.dart:123)
    at main$ (main.dart:7)
    at main (web_entrypoint.dart:19)
    at main.next (<anonymous>)
    at async_patch.dart:45
    at _RootZone.runUnary (zone.dart:1613)
    at _FutureListener.thenAwait.handleValue (future_impl.dart:155)
    at handleValueCallback (future_impl.dart:707)
    at Function._propagateToListeners (future_impl.dart:736)
    at _Future.new.[_completeWithValue] (future_impl.dart:542)
    at future.dart:401
    at _RootZone.runUnary (zone.dart:1613)
    at _FutureListener.then.handleValue (future_impl.dart:155)
    at handleValueCallback (future_impl.dart:707)
    at Function._propagateToListeners (future_impl.dart:736)
    at _Future.new.[_completeWithValue] (future_impl.dart:542)
    at async._AsyncCallbackEntry.new.callback (future_impl.dart:580)
    at Object._microtaskLoop (schedule_microtask.dart:40)
    at _startMicrotaskLoop (schedule_microtask.dart:49)
    at async_patch.dart:166

```

and

```
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
js_primitives.dart:30 The following JSNoSuchMethodError was thrown building MyApp(dirty):
js_primitives.dart:30 TypeError: Cannot read properties of undefined (reading 'app')
js_primitives.dart:30 
js_primitives.dart:30 The relevant error-causing widget was:
js_primitives.dart:30   MyApp file:///C:/Users/Neha/AndroidStudioProjects/devcom/lib/main.dart:10:10
js_primitives.dart:30 
js_primitives.dart:30 When the exception was thrown, this was the stack:
js_primitives.dart:30 C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 236:49  throw_
js_primitives.dart:30 packages/firebase_core_web/firebase_core_web.dart 73:3                                                                     _catchJSError
js_primitives.dart:30 packages/firebase_core_web/src/firebase_core_web.dart 138:13                                                               app
js_primitives.dart:30 packages/firebase_core/src/firebase.dart 55:41                                                                             app
js_primitives.dart:30 packages/firebase_auth/src/firebase_auth.dart 38:47                                                                        get instance
js_primitives.dart:30 packages/devcom/auth.dart 12:51                                                                                            new
js_primitives.dart:30 packages/devcom/main.dart 17:13                                                                                            build
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4648:28                                                                        build
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4574:15                                                                        performRebuild
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4267:5                                                                         rebuild
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4553:5                                                                         [_firstBuild]
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 4548:5                                                                         mount
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 3611:13                                                                        inflateWidget
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 3363:18                                                                        updateChild
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1189:16                                                                          [_rebuild]
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1159:5                                                                           mount
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1104:16                                                                          <fn>
js_primitives.dart:30 packages/flutter/src/widgets/framework.dart 2535:19                                                                        buildScope
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 1103:12                                                                          attachToRenderTree
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 936:24                                                                           attachRootWidget
js_primitives.dart:30 packages/flutter/src/widgets/binding.dart 917:7                                                                            <fn>
js_primitives.dart:30 C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 48:19       internalCallback
js_primitives.dart:30 
js_primitives.dart:30 ════════════════════════════════════════════════════════════════════════════════════════════════════

```

**`main.dart`**:

```
import 'package:flutter/material.dart';
import 'package:devcom/auth.dart';
import 'package:devcom/auth_provider.dart';
import 'package:devcom/root_page.dart';
import 'package:firebase_core/firebase_core.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return AuthProvider(
      auth: Auth(),
      child: MaterialApp(
        title: 'Flutter login demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: RootPage(),
      ),
    );
  }
}

```

**`index.html`** :

```html
<!DOCTYPE html>
  <html>
  <head>
    <!-- <script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-app.js" type = "module"></script>
    <script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-analytics.js" type = "module"> </script>
    <script src="https://www.gstatic.com/firebasejs/9.0.1/firebase-auth.js" type = "module"></script> -->
    <meta charset="UTF-8">
    <meta content="IE=Edge" http-equiv="X-UA-Compatible">
    <meta name="description" content="A new Flutter project.">

    <!-- iOS meta tags & icons -->
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <meta name="apple-mobile-web-app-title" content="devcom">
    <link rel="apple-touch-icon" href="icons/Icon-192.png">

    <!-- Favicon -->
    <link rel="shortcut icon" type="image/png" href="favicon.png" />

    <title>Devcom</title>
    <link rel="manifest" href="manifest.json">
  </head>
<body >
  <!-- The core Firebase JS SDK is always required and must be listed first -->

<script type="module"> 
  import { initializeApp } from 'https://www.gstatic.com/firebasejs/9.0.1/firebase-app.js';
  import {  } from 'https://www.gstatic.com/firebasejs/9.0.1/firebase-auth.js';
  import { getAnalytics } from "https://www.gstatic.com/firebasejs/9.0.1/firebase-analytics.js";

    const firebaseConfig = {
     apiKey: "...",
      authDomain: "......",
      databaseURL: ".....",
      projectId: "...",
      storageBucket: "",
      messagingSenderId: "",
      measurementId: "",
      appId: "1:.........:web:...........",
    };

    const app = initializeApp({ firebaseConfig });
// const app = getAnalytics({ firebaseConfig })    
</script>

 <script>
    var serviceWorkerVersion = null;
    var scriptLoaded = false;
    function loadMainDartJs() {
      if (scriptLoaded) {
        return;
      }
      scriptLoaded = true;
      var scriptTag = document.createElement('script');
      scriptTag.src = 'main.dart.js';
      scriptTag.type = 'application/javascript';
      document.body.append(scriptTag);
    }

    if ('serviceWorker' in navigator) {
      // Service workers are supported. Use them.
      window.addEventListener('load', function () {
        // Wait for registration to finish before dropping the <script> tag.
        // Otherwise, the browser will load the script multiple times,
        // potentially different versions.
        var serviceWorkerUrl = 'flutter_service_worker.js?v=' + serviceWorkerVersion;
        navigator.serviceWorker.register(serviceWorkerUrl)
          .then((reg) => {
            function waitForActivation(serviceWorker) {
              serviceWorker.addEventListener('statechange', () => {
                if (serviceWorker.state == 'activated') {
                  console.log('Installed new service worker.');
                  loadMainDartJs();
                }
              });
            }
            if (!reg.active && (reg.installing || reg.waiting)) {
              // No active web worker and we have installed or are installing
              // one for the first time. Simply wait for it to activate.
              waitForActivation(reg.installing ?? reg.waiting);
            } else if (!reg.active.scriptURL.endsWith(serviceWorkerVersion)) {
              // When the app updates the serviceWorkerVersion changes, so we
              // need to ask the service worker to update.
              console.log('New service worker available.');
              reg.update();
              waitForActivation(reg.installing);
            } else {
              // Existing service worker is still good.
              console.log('Loading app from service worker.');
              loadMainDartJs();
            }
          });

        // If service worker doesn't succeed in a reasonable amount of time,
        // fallback to plaint <script> tag.
        setTimeout(() => {
          if (!scriptLoaded) {
            console.warn(
              'Failed to load app from service worker. Falling back to plain <script> tag.',
            );
            loadMainDartJs();
          }
        }, 4000);
      });
    } else {
      // Service workers not supported. Just drop the <script> tag.
      loadMainDartJs();
    }
  </script>

</body>
</html>
```