为什么我会收到 404 错误，没有 Firebase 应用“[DEFAULT]”是什么意思？

Question

What does it exactly mean and how do I solve it?

Failed to load resource: the server responded with a status of 404 ()
firebaseNamespaceCore.ts:106 Uncaught FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call Firebase
App.initializeApp() (app/no-app).
     at f (https://www.gstatic.com/firebasejs/7.9.1/firebase.js:1:73499)
     at Object.i [as auth] (https://www.gstatic.com/firebasejs/7.9.1/firebase.js:1:73757)
     at https://superx-bcf15.web.app/:37:22

Answer 1

The error messages you provided are actually two separate errors.

The 404 Error

The first error message,

Failed to load resource: the server responded with a status of 404 ()

is caused by

<script src="js/app.js"></script>

where the file https://superx-bcf15.web.app/js/app.js doesn't exist.

The Firebase '[DEFAULT]' app

firebaseNamespaceCore.ts:106 Uncaught FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call FirebaseApp.initializeApp() (app/no-app).

This error message indicates that you haven't called firebase.initializeApp() to pass in the required configuration parameters before trying to use the SDK elsewhere.

In your code, you try to call firebase.auth() before calling firebase.initializeApp() here:

<script src="https://www.gstatic.com/firebasejs/7.9.1/firebase.js"></script>
<script>
    firebase.auth().onAuthStateChanged(function(user){
        if(user){
            window.location.href = "admin.html";
        }
    });
</script>

You need to change that to

<script src="https://www.gstatic.com/firebasejs/7.9.1/firebase.js"></script>
<script>
    firebase.initializeApp(/* your firebase config here */);
    firebase.auth().onAuthStateChanged(function(user){
        if(user){
            window.location.href = "admin.html";
        }
    });
</script>

These steps are well documented in the Getting Started documentation .

Because you are using Firebase Hosting, you can also use the built-in helper script to call initializeApp() with the configuration needed for your project automatically (as you can see here ):

<script src="https://www.gstatic.com/firebasejs/7.9.1/firebase.js"></script>
<script src="/__/firebase/init.js"></script>
<script>
    firebase.auth().onAuthStateChanged(function(user){
        if(user){
            window.location.href = "admin.html";
        }
    });
</script>