Wordpress Two Step Login

Question

I would like wp login form to have two steps authentication.

1.) If the username exists, ¹ password field appears.
2.) If the username doesn't exist, the password field is hidden.

¹ visitor must type correct username to proceed to step two.*

Where can I begin my quest to have the login form "detect usernames" in the DB?
If there is a better way, may you please share your idea?

Thanks for your attention,

Answer 1

Wordpress has the function username_exists. You should start there.

As for 'If there's a better way...'; I don't know what you want to achieve. It's looks like a lot of work for something that adds very little to the user experience and could cause security issues like Maggew said.