Can we know possible id/name attributes' values of username/password for input tag for all of the websites?

I want to implement password manager, for that I want to provide auto-fill functionalities for username and password.Is there any way I can get the exact field on the webpages (for almost all of the websites!!) ? some of the website uses while some has id="login-username". How to know all the possible values for id and name attribute for username and password field?