Is this the standard method to add the authentication on express with mongoose?

I cannot find any references, documentation, or articles on how to create the authentication functionality this way meaning that you create the method on UserShema that does authentication. During watching the video, I stopped it so that I could attempt before Dave going through the lesson. I basically used bcrypt.compare in index.js, pretty intuitive, I think. I know the object-oriented programming way is more elegant, but the problem is that I cannot find any written articles to implement the authentication, so I don't know if the Dave did is the typical standard way or just works for this particular application.