我试图在我的网站中添加Firebase身份验证。我试过这段代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>
Sample FirebaseUI App
</title>
<!-- ******************************************************************************************* * TODO(DEVELOPER): Paste the initialization snippet from: * Firebase Console > Overview > Add Firebase to your web app. * ***************************************************************************************** -->
<script type="text/javascript">
// Initialize Firebase
var config = {
apiKey: "AIzaSyB7cfgbxS4UgkGwsHyFgYwa6Ir7eRTWHM0",
authDomain: "web-teachinger.firebaseapp.com",
databaseURL: "https://web-teachinger.firebaseio.com",
projectId: "web-teachinger",
storageBucket: "",
messagingSenderId: "1070392376591"
};
firebase.initializeApp(config);
</script>
<script src="https://cdn.firebase.com/libs/firebaseui/2.5.1/firebaseui.js"></script>
<link type="text/css" rel="stylesheet" href="https://cdn.firebase.com/libs/firebaseui/2.5.1/firebaseui.css" />
<script type="text/javascript">
firebase.initializeApp(config);
// FirebaseUI config.
var uiConfig = {
signInSuccessUrl: 'success.html', signInOptions: [
// Leave the lines as is for the providers you want to offer your users.
firebase.auth.GoogleAuthProvider.PROVIDER_ID,
firebase.auth.FacebookAuthProvider.PROVIDER_ID,
firebase.auth.TwitterAuthProvider.PROVIDER_ID,
firebase.auth.GithubAuthProvider.PROVIDER_ID,
firebase.auth.EmailAuthProvider.PROVIDER_ID,
firebase.auth.PhoneAuthProvider.PROVIDER_ID
],
// Terms of service url.
tosUrl: 'TOS.php' };
// Initialize the FirebaseUI Widget using Firebase.
var ui = new firebaseui.auth.AuthUI(firebase.auth());
// The start method will wait until the DOM is loaded.
ui.start('#firebaseui-auth-container', uiConfig);
</script>
</head>
<body>
<!-- The surrounding HTML is left untouched by FirebaseUI. Your app may use that space for branding, controls and other customizations.-->
<h1>
Welcome to My Awesome App
</h1>
<div id="firebaseui-auth-container">
</div>
</body>
</html>
但是，当我访问Localhost时，它只显示“欢迎使用我的真棒应用程序”，并且没有使用身份验证提供程序，也没有看到容器。请帮助注意：您也可以在Localhost中测试此代码。
您在控制台中收到以下错误：Uncaught ReferenceError: firebase is not defined
您不包括Firebase JS CDN：<script src="https://www.gstatic.com/firebasejs/4.8.1/firebase.js"></script>