MEN Stack Session Auth Build and Run server.js

Learning objective: By the end of this lesson, students will be able to set up and run an Express server integrated with MongoDB, use environment variables for configuration, and include the proper middleware stack to process form requests.

Boilerplate express set-up

Let’s begin with the same boilerplate Express code and libraries we’ve come to know and love. As a quick reminder, this setup includes the essentials that you’ve already worked with in previous applications - Express for our web server framework, Mongoose for MongoDB interactions, Dotenv for managing our environment variables, EJS for templating, and Morgan for logging requests.

Install packages:

npm i express mongoose dotenv ejs morgan method-override

Create your .env file at the root level of the repository and include your MONGODB_URI connection string variable.

touch .env

Your .env should look like this:

MONGODB_URI=<connection-string-from-mongodb-atlas>

Add the following code to server.js:

const dotenv = require("dotenv");
dotenv.config();
const express = require("express");
const app = express();

const mongoose = require("mongoose");
const methodOverride = require("method-override");
const morgan = require("morgan");

// Set the port from environment variable or default to 3000
const port = process.env.PORT ? process.env.PORT : "3000";

mongoose.connect(process.env.MONGODB_URI);

mongoose.connection.on("connected", () => {
  console.log(`Connected to MongoDB ${mongoose.connection.name}.`);
});

// Middleware to parse URL-encoded data from forms
app.use(express.urlencoded({ extended: false }));
// Middleware for using HTTP verbs such as PUT or DELETE
app.use(methodOverride("_method"));
// Morgan for logging HTTP requests
app.use(morgan('dev'));

app.listen(port, () => {
  console.log(`The express app is ready on port ${port}!`);
});

process.env.what ?

You probably noticed a new port variable we’re defining and using in the app.listen statement. This will come in handy when we’re deploying our applications and cannot know in advance which port the hosting service will use.

The syntax commonly used to set this variable is a ternary statement, which is essentially a condensed if...else statement. You could replace it with the following:

let port;
if (process.env.PORT) {
  port = process.env.PORT;
} else {
  port = 3000;
}

The ternary statement decides which value to assign to the variable. If the process.env.PORT variable is defined and has a ‘truthy’ value, then that value is set as the port number. Otherwise, if it’s ‘falsy’ (undefined or holding no value), the default port 3000 is used. This way, we get to use the environment variable in a hosted environment, and still use 3000 when running the application locally.

Run the server.js

Let’s confirm the application is working before moving on. Run server.js and confirm you’ve received the mongoose connection message.

nodemon

You should see something in your terminal like:

Connected to MongoDB <mongoose-uri>.
The express app is ready on port 3000!