1. Webservers and Express.js

What is a Web Server?

• A piece of software that listens on a specific port for HTTP requests from clients
  • Typically port 80 for HTTP requessts and 443 for HTTPS requeests
• When a request is made, the web server sends back the client a response (such as a HTML or JSON file)
• Common responsibilities include:
  • Serving static files (HTML, CSS, JS)
  • Handling form submissions
  • Executing server-side code
  • Managing APIs
  • Logging requests and errors
  • Managing sessions, authentication, and more
• Some common web servers are:
  • Apache HTTP Server: One of the oldest and most widely used web servers.
  • Nginx: Known for its high performance and ability to handle a large number of concurrent connections. It’s often used as a load balancer
  • Caddy: A modern web server written in Go that automatically handles HTTPS by default, known for it’s easy setup and ability to handle lots of connections

What is Express.js?

• Express.js is a Node.js framework that simplifies the process of creating a web application
  • Express provides tooling to build the back end of a web application in Javascript using Node.js as the web server
• Express.js aims to be a rather minimal framework by default, allowing users to bring in extra functionality through the use of plugins
  • i.e. You could find a plugin to handle user authentication in an Express.js server, so you don’t have to write all that code yourself

Why Express.js?

• Express.js allows you to easily write your backend web server in the same language as your front end
• Makes it easy to add custom middleware to handle incoming requests
  • Middleware: Functions that go between the incoming requests and the logic used to process a specific request
    • Example: File upload server
      • User clicks the button to upload a new file, but user’s must be authenticated before uploading
      • Middleware would live between the incoming upload request and the actual upload code and would check if the user is authenticated
      • That way, the file upload doesn’t need to check authentication itself, and we only have to write those authentication checks once
    • Middleware can be used for lots of things, like handling user cookies, parsing incoming data, logging requests, etc.
• Express.js has a huge ecosystem around it
  • That means it’s plugin support can be truly realized, as there are plugins for almost everything
• It scales really well, due to Node.js non-blocking I/O and event-driven nature
  • Meaning it can handle large volumes of requests and is not just for small apps

Summary:

Express.js acts as a thin layer on top of Node.js, simplifying the process of handling HTTP requests, routing, and generating responses. It’s a powerful yet simple framework for building modern web servers.