How, when clicking on a link, check if there is an administrator session, and if so, redirect to admin, and if not, then stay on the same page?

Question

JavaScript

There is a link on the site Authorization
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The server is written in express.
When you click on the link, you need to check if there is an administrator session, if there is one without authorization (it appears if there is no session, this is not a new page, but a separate block that is initially hidden on the welcome page) redirect to the Admin and stop the handler on the link. If there is no administrator session, then execute the following code (it opens the block with the authorization form).

Answer 1

check by localStorage or cookie