Authorization via VK on the client?

Question

PHP

There is an application written in pure JS that generates html code and communicates with the server using requests.
It is necessary to implement authorization through VK.
The current procedure:
1. The user clicks on VK, a new window opens where VK is logged
in 2. In this window, a redirect is made to our server, where user data is collected (id, first name, last name ...)
3. A regular token is generated
4? How to pass the token back to the client to complete the authorization?
The js application works by itself and a redirect from the server will not help, some way is needed to transfer the token to the client.

Answer 1

Two different options for user authorization in VK :
Now you have implemented the 2nd. And you want the 1st.