Authentication System using Passport.js, Node.js, and MongoDB - Part 2: Local Sign up and Sign in

Authentication is used to verify a customer's identity using an email/password or a social login like Google, Facebook etc. Passport.js makes it easy to set up OAuth2 login strategies from all identity providers and acts a uniform interface between the user and the application. Build a local sign up/sign in button to authenticate users using a traditional email and password Save and manage user data in MongoDB Give useful notifications using Express Flash to the user.