Facebook login & Google Login through oauth 2.0( like stackoverflow fb & google login)

Question

I want to give easy login option to the users of my website through Facebook login. I have done the login properly through JavaScript SDK easily through the procedure given in the official Doc of Facebook Developer Console. I have used the code from HERE

Its working fine but the issue is I have to load my js each time when my page reloads that increases my page load at initial time during home page.

I tried studying the Stack overflow Login system for Google and Facebook and found that at the login page its not loading any js, Its working on oauth 2.0.

I searched for it but still couldn't find any useful document or code for doing so.