How to Access Firebase's Authentication Persistence Manager Keys?

I am running a web app with Firebase redirect authentication.

When the user is returned to the web app, the web app initializes once more while the authentication redirect is pending.

This state can be seen in the browser session storage, like this:

{firebase:pendingRedirect:XXXXXXXXXXXXXXXXXXXXXXXXXXX:[DEFAULT]: '"true"'}

I want to retrieve this item in an idiomatic way. Right now I am using this util:

function getAuthRedirectIsPending() {
  for (let i = 0; i < sessionStorage.length; i++) {
    const key = sessionStorage.key(i)
    if (
      key?.startsWith('firebase:pendingRedirect') &&
      sessionStorage.getItem(key) === '"true"'
    ) {
      return true
    }
  }
  return false
}

But I also noticed that this key exists on the firebase auth object, albeit inaccessible:

{
    "persistenceManager": {
        ...
        "fullUserKey": "firebase:authUser:XXXXXXXXXXXXXXXXXXXXXXXXXXX:[DEFAULT]",
        "fullPersistenceKey": "firebase:persistence:XXXXXXXXXXXXXXXXXXXXXXXXXXX:[DEFAULT]"
}

I was wondering if there was a way to retrieve the persistence redirect key name from Firebase, then using it to access the window session storage?

Firebase Authentication Persistence Manager uses the Web Storage API to store user authentication tokens. The Web Storage API is a simple key-value storage system that provides two types of storage mechanisms: session storage and local storage.

The session storage is a temporary storage mechanism that is cleared when the user closes the browser window or tab, while the local storage persists even after the user closes the browser window or tab.

Firebase Authentication Persistence Manager stores the user authentication tokens in the local storage, and the keys for the local storage are accessible through the browser's developer console.

To access the Firebase Authentication Persistence Manager keys, follow these steps:

Open your web application in your browser and navigate to the authentication page.

Open the browser's developer console by pressing F12 or right-clicking on the page and selecting "Inspect."

In the developer console, select the "Application" tab.

In the "Application" tab, expand the "Local Storage" option.

Look for the Firebase Authentication Persistence Manager keys. The keys are named "firebase:authUser" followed by your Firebase project ID.

Click on the key to view the stored value, which will include the user's authentication token.

Note: Accessing the user authentication token may not be necessary in most cases, as Firebase Authentication provides methods to manage user authentication state without directly accessing the authentication token. Additionally, manipulating the authentication token can be dangerous and could compromise the security of your application.