If you're looking to delve deeper into PassportJS authentication, check out this insightful blog post: Passport authentication. I've included additional comments where necessary. All you have to do is tweak the code from fetching user data from a database to pulling it from a JSON file.
// config/passport.js
// necessary modules
var LocalStrategy = require('passport-local').Strategy;
// importing users' JSON data
var User = require('../app/data/users');
// export the module function for app use
module.exports = function(passport) {
// =========================================================================
// passport session setup ==================================================
// =========================================================================
// required for persistent login sessions
// needed for serializing and deserializing users in/out of session
// serialize user for the session
passport.serializeUser(function(user, done) {
done(null, user.id);
});
// deserialize the user
passport.deserializeUser(function(id, done) {
// Implement logic to retrieve user from json data using userID
// Return done({}) if not found
// Otherwise, return done(null, userObject);
});
// =========================================================================
// using named strategies for login and signup
// defaults to 'local' if no specified name
passport.use('local-login', new LocalStrategy({
// override default username and password with email
usernameField : 'email',
passwordField : 'password',
passReqToCallback : true // pass entire request back to callback
},
function(req, email, password, done) { // callback with form email and password
// Find user in json data based on email
// Validate password
// If user not found or incorrect password, return done({})
// Else return done(null, userObject);
}));
};