问在firebase托管之后，我得到了错误"firebase没有被定义“

EN

<!-- update the version number as needed -->
<script defer src="/__/firebase/7.4.0/firebase-app.js"></script>
<!-- include only the Firebase features as you need -->
<script defer src="/__/firebase/7.4.0/firebase-auth.js"></script>
<script defer src="/__/firebase/7.4.0/firebase-database.js"></script>
<script defer src="/__/firebase/7.4.0/firebase-messaging.js"></script>
<script defer src="/__/firebase/7.4.0/firebase-storage.js"></script>
<!-- initialize the SDK after all desired features are loaded -->
<script defer src="/__/firebase/init.js"></script>
<script src="/javascripts/sessionchk.js"></script>

firebase.auth().onAuthStateChanged(function(user) {
        if (user) {
            document.getElementById("loginmenu").textContent = "logout";
            document.getElementById("loginmenu").href = "/logout";
        } else {
            document.getElementById("loginmenu").textContent = "login";
            document.getElementById("loginmenu").href = "/loginform";
        }
    });