app.js

var express = require("express");
var bodyParser = require("body-parser");
var mongoose = require("mongoose");
var session = require("express-session");
var MongoStore = require("connect-mongo")(session);
var app = express();

// mongodb connection
mongoose.connect("mongodb://localhost:27017/bookworm");
var db = mongoose.connection;
// mongo error
db.on("error", console.error.bind(console, "connection error:"));

// use sessions for tracking logins
app.use(
  session({
    secret: "treehouse loves you",
    resave: true,
    saveUninitialized: false,
    store: new MongoStore({
      mongooseConnection: db
    })
  })
);

// make user ID available in templates
app.use(function(req, res, next) {
  res.locals.currentUser = req.session.userId;
  next();
});

// parse incoming requests
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

// serve static files from /public
app.use(express.static(__dirname + "/public"));

// view engine setup
app.set("view engine", "pug");
app.set("views", __dirname + "/views");

// include routes
var routes = require("./routes/index");
app.use("/", routes);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error("File Not Found");
  err.status = 404;
  next(err);
});

// error handler
// define as the last app.use callback
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.render("error", {
    message: err.message,
    error: {}
  });
});

// listen on port 3000
app.listen(3000, function() {
  console.log("Express app listening on port 3000");
});