Node.js Study Guide

Introduction to Node.js

What is Node.js?

Node.js is an open-source, cross-platform JavaScript runtime environment that allows developers to execute JavaScript code outside of a web browser. Unlike traditional JavaScript that runs in browsers and is primarily used for front-end development, Node.js enables developers to build server-side applications using JavaScript. It is built on the V8 JavaScript engine from Google, which is known for its performance and is also used in the Chrome browser.

History of Node.js

Node.js was created by Ryan Dahl in 2009. Dahl was motivated to create Node.js due to the limitations of the most popular web server of the time, Apache HTTP Server, especially its performance issues with concurrent connections. He introduced Node.js at the inaugural European JSConf on November 8, 2009. The platform gained immediate popularity within the developer community due to its unique approach to non-blocking, event-driven I/O, which optimized throughput and scalability for web applications with many I/O operations.

Since its inception, Node.js has seen numerous releases and updates, with contributions from a vibrant community and backing from various tech giants. The Node.js Foundation, established in 2015, oversees the development and maintenance of Node.js to ensure its continued growth and relevance.


Non-blocking I/O: Node.js operates on a single-threaded event loop using non-blocking I/O calls, allowing it to handle thousands of concurrent connections without incurring the cost of thread context switching.

Performance: With the V8 engine at its core, Node.js offers impressive speed and runtime efficiency.

Unified Development: Developers can use JavaScript for both server-side and client-side scripting, leading to a more cohesive and efficient development process.

Rich Ecosystem: The Node Package Manager (NPM) provides a vast library of reusable packages, making it easier to develop and deploy applications.

Scalability: Node.js is designed with scalability in mind, making it suitable for large-scale applications and microservices architectures.

Use Cases

Web Applications: From simple websites to complex web applications, Node.js is a popular choice for web development.

Real-time Applications: Due to it’s non-blocking nature, Node.js is ideal for real-time applications like chat applications, online gaming, and live-tracking systems.

APIs and Microservices: Node.js’ lightweight nature makes it perfect for developing RESTful APIs and microservices.

Data Streaming: Node.js can read and write streams of data, making it suitable for video or audio encoding and proxying between different data sources.

In conclusion, Node.js has revolutionized the way developers approach server-side programming by bringing JavaScript, traditionally a front-end language, to the back end. Its non-blocking, event-driven architecture makes it a top choice for modern web applications, especially those requiring real-time functionality and high concurrency.

Basics of Node.js

Understanding the Architecture

  1. Event Loop

The event loop is the heart of Node.js’s non-blocking I/O mechanism. It allows Node.js to handle many connections concurrently, making it highly scalable. Here’s how it works:

  • When a Node.js application starts, it initializes the event loop, processes the provided input script (which may make asynchronous API calls, schedule timers, or call process.nextTick()), and then begins processing the event loop.
  • The event loop continually checks if there are tasks to be executed, and if there are, it executes them, otherwise, it remains in a waiting state.
  • It’s essential to understand that JavaScript executed by Node.js is run in a single thread, but many of the I/O operations (like network, database, or file system operations) run in separate threads because they are provided by the libuv library which Node.js is built on. This is how Node.js can be single-threaded but still support concurrency.

Erik August Johnson is a software developer working with JavaScript to build useful things. Follow them on Twitter.