Social Network (Facebook, Twitter, etc) User Account Integration (duplicate scenario)

Question

So there are definitely many tutorials out there regarding how to integrate various individual social network authentication/registration into existing user accounts. But the s

Answer 1

I have been contemplating adding FB auth to our app, but we know that our returning users might click it and complete checkout for a new item, and then be surprised to not see any of their existing orders. To solve this, when a user clicks the 'Login with Facebook' item, we are using that click to fire a dropdown menu with two options:

[ Login with Facebook ]
[ Create new account ]
[ I have an account ]

If the user clicks 'I have an account' we send them to FB auth and return email from FB to our app. We compare that email to our existing users. If we match, we add the FB creds to the user. If no match, we throw an alert:

The email you have with FB does not match any of our accounts. To log in to your existing account, login with your email below, or update the email in your Facebook account

This allows the user to create a whole new account, if they want to keep them separate, without needing a new email service. While this is an edge case, it is a feature.