firebase.initializeApp回调/承诺？ [英] firebase.initializeApp callback/promise?
问题描述
<！DOCTYPE html>
< html>
< head>
< meta charset =utf-8>
< meta http-equiv =X-UA-Compatiblecontent =IE = edge>
< meta name =viewportcontent =width = device-width，initial-scale = 1>
< title> Calcolo Diliuzioni< / title>
< / head>
< body>
< h1>我的应用< / h1>
<！ - Libreria per gestire l'autenticazione con google - >
< script src =https://apis.google.com/js/platform.jsasync defer>< / script>
<！ - Firebae config - >
< script src =https://www.gstatic.com/firebasejs/live/3.0/firebase.js>< / script>
< script>
//初始化Firebase
var config = {
apiKey：，
authDomain：，
databaseURL：，
storageBucket： ，
};
firebase.initializeApp（config）;
< / script>
< script type =text / javascript>
var user = firebase.auth（）。currentUser;
if（user）{
console.log（user）;
} else {
console.log（user）;
}
< / script>
< / body>
< / html>
假设我有一个已经登录的用户。当我在控制台中加载页面时，我得到了 null 。如果我在浏览器控制台中运行相同的代码
pre>
var user = firebase.auth（）。currentUser;
if（user）{
console.log（user）;
} else {
console.log（user）;
}
我可以获取当前用户的对象。
$ b我认为 firebase.initializeApp（config）; 有一些异步行为。什么是正确的解决方法？我应该在 firebase.initializeApp（config）; 函数上使用承诺或其他东西吗？一种回调。
initialize app是同步的。但是，确定当前用户状态是异步的。确定当前auth状态的正确方法是使用观察者：
https://firebase.google.com/docs/auth/web/manage-users
firebase.auth （）.onAuthStateChanged（function（user）{
if（user）{
//用户登录且currentUser不再返回null
} else {
//没有用户登录。
}
}）;
This is my web page
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Calcolo Diliuzioni</title>
</head>
<body>
<h1>My app</h1>
<!-- Libreria per gestire l'autenticazione con google -->
<script src="https://apis.google.com/js/platform.js" async defer></script>
<!-- Firebae config -->
<script src="https://www.gstatic.com/firebasejs/live/3.0/firebase.js"></script>
<script>
// Initialize Firebase
var config = {
apiKey: "",
authDomain: "",
databaseURL: "",
storageBucket: "",
};
firebase.initializeApp(config);
</script>
<script type="text/javascript">
var user = firebase.auth().currentUser;
if (user) {
console.log(user);
} else {
console.log(user);
}
</script>
</body>
</html>
Let's assume I have an already logged user. When I load the page in the console I got null. While I'm expecting to have the current user's object.
If I run the same code in the browser console
var user = firebase.auth().currentUser;
if (user) {
console.log(user);
} else {
console.log(user);
}
I'm able to get the current user's object.
I think that the firebase.initializeApp(config); has some async behavior. What's the right way to work around it? Should I use a promise or something on the firebase.initializeApp(config); function? A sort of callback..
initialize app is synchronous. However, determining the current user state is asynchronous. The right way to determine the current auth state is to use an observer: https://firebase.google.com/docs/auth/web/manage-users
firebase.auth().onAuthStateChanged(function(user) {
if (user) {
// User is signed in and currentUser will no longer return null.
} else {
// No user is signed in.
}
});
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