Firebase 身份验证 onAuthStateChanged 在函数主体后响应

Question

I am creating an application with firebase. When loading any page, I am checking for authentication via following code. When I call isAuthenticated from landing page, its returning false even though user is already logged in and persistence is LOCAL( https://firebase.google.com/docs/auth/web/auth-state-persistence ), after false returned the inner function is executed.

authentication.ts

import {auth} from "../firebase";

export function isAuthenticated() {
    console.log("Started!");
    auth.onAuthStateChanged(function(user) : boolean {
        console.log("Coming inside authentication");
        if (user) {
            console.log('User signed in - auth success! ', user.email);
            return true;
        } else {
            console.log('User not signed in - auth failed! ');
            return false;
        }
    });
    console.log("Something wrong, coming here!");
    return false;
};

I am getting false even before the inner onAuthStateChanged function runs. Please look at the screen shot.

How to make sure I always get return value of inner function.

Answer 1

auth.onAuthStateChanged doesn't return anything helpful. It adds a listener asynchronously that gets invoked whenever the user signs in or out. It's not very useful for knowing the user state immediately, and you can't simply return a value out of the callback for use in an enclosing function.

If you want to know immediately if a user is currently signs in or out, you should just use auth.currentUser to get a User object. It will be null if the user is signed out. However, this status can change over time. If you're interested in changes over time, use the listener instead.