setuppassport.js

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

var User = require("./models/user");

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

  passport.deserializeUser(function (id, done) {
     User.findById(id, function (err, user) {
        done(err, user);
     });
  });

  passport.use("login", new LocalStrategy(function (username, password, done) {
      User.findOne({ username: username }, function (err, user) {
         if (err) { return done(err); }
         if (!user) {
             return done(null, false, { message: "No user has that username!" });
         }
         user.checkPassword(password, function (err, isMatch) {
             if (err) { return done(err); }
             if (isMatch) {
                 return done(null, user);
             } else {
                 return done(null, false, { message: "Invalid password." });
             }
         });
      });
  }));
};