passport.js

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;

passport.serializeUser(function (user, done) {
  done(null, user._id);
});

passport.deserializeUser(function (id, done) {
  User.findOne({_id: id}, function (err, user) {
    done(err, user);
  })
});

passport.use(new LocalStrategy({
    usernameField: 'email'
  },
  function (username, password, done) {
    User.findOne({email: username}, function (err, user) {
      if (err) return done(err);
      if (!user) {
        return done(null, false, {
          message: 'Incorrect username or password.'
        });
      }
      if (!user.validPassword(password)) {
        return done(null, false, {
          message: 'Incorrect username or password.'
        });
      }

      return done(null, user);
    })
  }
));