You’ll hear the word “Node.js” if you’re considering using JavaScript for back-end development. Node is frequently linked to the creation of potent web servers.

But exactly what is Node.js? Is it, like Angular, a JavaScript framework? Is it a language for programming? Is it a library for JavaScript? Is it a catch-all phrase for a collection of technologies? Or is it really a different name for JavaScript?

We will delve into the world of Node.js in this post, discovering what it is, why it was developed, and what it can be used for. This course is not project-based; rather, it seeks to expose new users to Node and its functionality.

You’ll like reading this article if you’re curious to understand more about software tools and how they operate. So with that, let’s get started.

History of Node.js

In 1995, Brendan Eich, a Netscape employee, created JavaScript. However, it was written in a computer language that could only be used with a browser.

Initially, static data was the only thing displayed on web pages. The requirement for greater interactive behavior within web pages was met with the creation of JavaScript. Developers may create more dynamic web sites thanks to this technology.

Companies tried using JavaScript, which Brendan Eich created, to run web servers as well (server-side scripting). These efforts included Microsoft’s Active Server Pages and Netscape’s Livewire.

However, despite JavaScript’s ongoing rise in popularity when used in browsers, this method of creating web servers was never adopted.

Google unveiled Chrome, a revolutionary web browser, in 2008. When it was first published, this browser completely changed how people access the internet. It is an optimized browser that runs JavaScript quickly and has enhanced the web browsing experience.

The fact that Google Chrome runs the V8 JavaScript engine inside of it allowed it to execute JavaScript code so quickly. It was the engine’s job to accept JavaScript code, optimize it, and then run it on the computer.

The engine served as an appropriate client-side JavaScript solution. Google Chrome has emerged as the top web browser.

A software programmer by the name of Ryan Dahl questioned the then-common practice of running back-end servers in 2009. The Apache HTTP Server was the most widely used program for creating web servers. Dahl asserted that it had limitations because it couldn’t successfully handle a high volume of real-time user connections (10,000+).

This was one of the key motivations behind Ryan Dahl’s creation of the utility Node.js. Outside of a browser, Node.js uses Google’s V8 engine to interpret and run JavaScript code. It was an application designed to manage Web servers.

Node.js was a fantastic replacement for the conventional Apache HTTP server and gradually won over the development community.

Many large companies today employ Node.js, including Netflix, NASA, LinkedIn, Paypal, and many others. These businesses make use of Node.js’ features to create powerful applications for their users.

Additionally, at the time this article was being written, Node.js was the most well-liked technology in the “Web Frameworks and Technology” category of the most current StackOverflow Developer Survey. This further demonstrates how well-liked Node.js is right now.

This article will go in-depth to look at what makes Node.js stand out, and how it works. But before that, we need to define exactly what it is.

What is Node.js?

From the Node.js official Website, it states that:

Node.js is an open-source, cross-platform JavaScript Runtime Environment.

For us to define Node.js, we need to break the definition into parts. The terms we’ll define are:

  • open-source
  • cross-platform
  • Runtime Environment

What does open source mean?

In general, the term “open source” refers to software whose source code is available for public inspection and modification. This implies that anyone can examine the code that enables the software to function as it does.

The program’s users gain a deeper understanding of the program’s capabilities as a result, which is a benefit. Additionally, if someone finds a bug, they can help to fixing it.

The most well-known website for showing Open Source code, GitHub, hosts Node’s source code. On GitHub, Node.js receives a lot of contributions from users who add functionality and repair bugs. Everyone gets access to the Node.js source code and is free to create their own customized version of the software if they so choose.

What does cross-platform mean?

If a program is cross-platform, it means that the program is not limited to a single Operating System or hardware architecture.

A cross-platform program can run on multiple platforms. Node.js runs on Windows, Linux, Unix, and MacOS among other platforms. Developers can use Node.js on a lot of operating systems.

What is a runtime environment?

Any setting where a user can run code created in a particular programming language is referred to as the runtime environment of that language. All the equipment and materials required to run the code are available in that environment. A JavaScript runtime environment is Node.js.

In addition to Node.js, a web browser is another illustration of a JavaScript runtime environment. Most of the time, a browser has everything needed to run client-side JavaScript code.

JavaScript can be used in the browser to interact with the markup components and change the style. Since the browser is a runtime environment, it immediately executes the code.

You can see that Node.js is not a JavaScript framework like Angular from the three definitions of the terminology given above. The term “Node.js” does not refer to a programming language, a JavaScript library, or a collection of technologies. It is not a different name for JavaScript either.

Software that can run JavaScript code is called Node.js. Node.js is a JavaScript runtime environment, to put it another way. It is a setting created to enable the use of JavaScript scripting for server-side scripting.

How Does Node.js Work?

Node.js was written mostly with C/C++. As a program that is supposed to run web servers, Node.js needs to constantly interact with a device’s operating system.

Building Node.js with a low-level language like C made it easy for the software to access the operating system’s resources and use them to execute instructions.

But there are many more intricacies involved in how Node.js works. Node.js runs fast and efficient web servers but how exactly does it do that? This section explains the process Node.js uses to achieve its efficiency.

There are three main components we must understand to see how Node.js works. These components are:

  • V8 Engine
  • Libuv
  • Event Loop

We’ll dive into detail and explain each of these components, and how they make up Node.js.

What is the V8 Engine?

The V8 Engine is the JavaScript engine that interprets and runs JavaScript code in the Chrome browser. Some other browsers use a different engine, for example, Firefox uses SpiderMonkey, and Safari uses JavaScriptCore. Without the JavaScript engine, a computer can not understand JavaScript.

The V8 engine contains a memory heap and call stack. They are the building blocks for the V8 engine. They help manage the execution of JavaScript code.

The memory heap is the data store of the V8 engine. Whenever we create a variable that holds an object or function in JavaScript, the engine saves that value in the memory heap. To keep things simple, it is similar to a backpack that stores supplies for a hiker.

Whenever the engine is executing code and comes across any of those variables, it looks up the actual value from the memory heap – just like whenever a hiker is feeling cold and wants to start a fire, they can look into their backpack for a lighter.

There is a lot more depth to understanding the memory heap. Memory management in JavaScript is a topic that takes more time to explain because the real process is highly intricate.

The call stack is another building block in the V8 engine. It is a data structure that manages the order of functions to be executed. Whenever the program invokes a function, the function is placed on the call stack and can only leave the stack when the engine has handled that function.

JavaScript is a single-threaded language, which means that it can only execute one instruction at a time. Since the call stack contains the order of instructions to be executed, it means that the JavaScript engine has just one order, one call stack.

What is Libuv?

Apart from the V8 engine, another very important component of Node.js is Libuv. Libuv is a C library used for performing Input/output (I/O) operations.

I/O operations have to do with sending requests to the computer and receiving responses. These operations include reading and writing files, making network requests, and so on.

From Libuv’s official website, they state that:

Libuv is a multi-platform support Library with a focus on asynchronous I/O.

This means that Libuv is cross-platform (can run on any operating system) and has a focus on Asynchronous I/O.

The computer tends to take time to process I/O instructions, but Libuv—the library Node.js uses to interface with the computer— is focused on Asynchronous I/O. It can handle more than one I/O operation at once.

This is what makes Node.js process I/O instructions efficiently despite being single-threaded. It is all because of Libuv. Libuv knows how to handle requests asynchronously, thereby minimizing delay. But how exactly does the JavaScript engine make use of Libuv?

Whenever we pass a script to Node.js, the engine parses the code and starts processing it. The call stack holds the invoked functions and keeps track of the program. If the V8 engine comes across an I/O operation, it passes that operation over to Libuv. Libuv then executes the I/O operation.

Note that Libuv is a C Library. How do we use JavaScript code to run C instructions? There are bindings that connect JavaScript functions to their actual implementation in Libuv. These bindings make it possible to use JavaScript code for I/O instructions.

Node.js uses Libuv for the actual implementation but exposes Application Programming Interfaces (APIs). So, we can now use a Node.js API (which looks like a JavaScript function) to initiate an I/O operation.

One interesting thing to note is that it is true that JavaScript is a single-threaded language, but Libuv—the low-level library Node.js uses— can make use of a thread pool (multiple threads) when executing instructions in the operating system.

Now, you don’t have to worry about these threads when using Node.js. Libuv knows how to manage them effectively. You just have to make use of the provided Node.js APIs to write the instructions.

Libuv was originally created for Node.js, but different programming languages now have bindings for it. Julia and Luvit (Lua-based Runtime Environment) have the bindings built in just like Node.js, but other languages have libraries that provide those bindings. An example is uvloop in Python, among others.

What is an Event Loop?

The Event Loop in Node.js is a very important part of the process. From the name, we can see it is a loop. The loop starts running as Node.js begins executing a program. In this section, we’ll examine what the event loop does.

When we run our JavaScript program that contains some asynchronous code (like I/O instructions or timer-based actions), Node.js handles them using the Node.js APIs. Asynchronous functions usually have instructions to be executed after the function has finished processing. Those instructions are placed in a Callback Queue.

The Callback Queue works with the First In First Out (FIFO) approach. That means the first instruction (callback) to enter the queue is the first to be invoked.

As the event loop runs, it checks if the call stack is empty. If the call stack is not empty, it allows the ongoing process to continue. But if the call stack is empty, it sends the first instruction on the callback queue to the JavaScript engine. The engine then places that instruction (function) on the call stack and executes it. This is very similar to how the event loop works in the browser.

So, the event loop executes callbacks from asynchronous instructions using the JavaScript V8 engine in Node.js. And it is a loop, which means every time it runs, it checks the call stack to know if it will remove the foremost callback and send it to the JavaScript engine.

Node.js is said to have an event-driven architecture. This means Node.js is built around listening to events and reacting to them promptly when they happen. These events can be timer events, network events, and so on.

Node.js responds to those events by using an event loop to load event callbacks to the engine after something triggers an event. It is for this reason that Node.js is excellent for real-time data transfer in applications.

Modules in Node.js

A lot of the functionality of Node.js is housed in modules that come with the software. These modules are meant to split the building blocks of programs into manageable chunks like Lego blocks. With this in place, we only have to import the modules we need for our programs.

For example, the piece of code below imports a built-in module called fs.

const fs = require('node:fs')

But there are other ways we can use modules in Node.js. Apart from the built-in modules, we can also use modules (or packages) other developers built.

Node Package Manager (NPM) is a software application that comes together with Node.js. It manages all the third-party modules that are available in Node.js. Whenever you need a third-party package, you install it from NPM using the npm install command.

To import a module you installed from NPM would look something like this:

const newModule = require('newModule')

Node.js Looking Forward

Node.js has a large community of developers now. It has thousands of contributors on GitHub and is used by some of the biggest companies today. But what does the future look like for Node.js?

Node.js has evolved well since it came into existence in 2009. It was originally made for back-end development, but it can do so much more now. You can use Node.js to develop desktop applications, front-end web applications, mobile applications, and command-line tools. Developers will continue to use it for more and more of these applications.

Ryan Dahl —the inventor of Node.js— announced a new JavaScript Runtime in 2018 called Deno. He unveiled this Runtime he co-created in a talk titled “10 Things I Regret about Node.js”.

Deno is a JavaScript Runtime Environment based on Google Chrome’s V8 engine but written in Rust. Deno is not only a Runtime environment for JavaScript but also TypeScript.

Ryan Dahl created Deno because he decided he had made some wrong decisions concerning the original blueprint of Node.js. He wanted to make better architectural decisions for a JavaScript Runtime environment for Web Servers. The result was Deno.

But Deno is yet to see massive adoption in the Developer Community. It is still a relatively new technology and needs more time to gain ground.

Also, the OpenJS Foundation which is the organization actively managing, developing, and maintaining Node.js has been fixing some of the bugs and the ultimate efficiency of Node.js. More projects are built on top of the Node.js architecture, and that will likely continue to be the case for the foreseeable future.


In this article, you have learned a lot and can now confidently answer the question “What exactly is Node.js?”.

We started by going over the history of Node.js, then properly defined Node.js. After that we elaborated on how Node.js works, explaining components such as the V8 Engine, Libuv, and Event Loop.

After that, we talked about modules in Node.js and NPM. Finally, we looked at what the future could hold for Node.js, and we concluded it will likely only power even more applications.

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