Overview

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.

The event loop is what allows Node.js to perform non-blocking I/O operations — despite the fact that JavaScript is single-threaded — by offloading operations to the system kernel whenever possible.

Blocking is when the execution of additional JavaScript in the Node.js process must wait until a non-JavaScript operation completes. This happens because the event loop is unable to continue running JavaScript while a blocking operation is occurring.

In Node.js, JavaScript that exhibits poor performance due to being CPU intensive rather than waiting on a non-JavaScript operation, such as I/O, isn't typically referred to as blocking. Synchronous methods in the Node.js standard library that use libuv are the most commonly used blocking operations. Native modules may also have blocking methods.

All of the I/O methods in the Node.js standard library provide asynchronous versions, which are non-blocking, and accept callback functions. Some methods also have blocking counterparts, which have names that end with Sync.

Blocking methods execute synchronously and non-blocking methods execute asynchronously.

Docker allows you to package an application with all of its dependencies into a standardized unit, called a container, for software development. A container is a stripped-to-basics version of a Linux operating system. An image is software you load into a container.

The Timers module in Node.js contains functions that execute code after a set period of time. Timers do not need to be imported via require(), since all the methods are available globally to emulate the browser JavaScript API. To fully understand when timer functions will be executed, it's a good idea to read up on the the Node.js Event Loop.

Prerequisites

Before proceeding with this tutorial, you should have a basic understanding of JavaScript. As we are going to develop web-based applications using Node.js, it will be good if you have some understanding of other web technologies such as HTML, CSS, AJAX, etc.