One of the most important things that people get confused about while getting introduced to Node.js is understanding what, exactly, it is. Is it a different language altogether, is it just a framework on top of it, or is it something else? Node.js is definitely not a new language, and it is not just a framework on JavaScript. It can be considered as a runtime environment for JavaScript built on top of Google's V8 engine. So, it provides us with a context where we can write JavaScript code on any platform where Node.js can be installed. Anywhere!

Now, a bit about its history! Back in 2009, Ryan Dahl gave a presentation at JSConf that changed JavaScript forever. During his presentation, he introduced Node.js to the JavaScript community. He concluded it after a roughly 45-minute talk, receiving a standing ovation from the audience in the process. He was inspired to write Node.js after he saw a simple file upload progress bar on Flickr, the image-sharing site. Realizing that the site was going about the whole process the wrong way, he decided that there had to be a better solution.

Now let's go through the features of Node.js, which make it unique from other server-side programming languages.

The V8 engine was developed by Google and was open sourced in 2008. As we all know, JavaScript is an interpreted language and it will not be as efficient as a compiled language, as each line of code gets interpreted one by one while the code gets executed. The V8 engine brings in an efficient model, where the JavaScript code is first interpreted and then compiled into machine-level code.

The new V8 5.9 provides a stable release that introduces TurboFan compiler which provides performance and mass optimization benefits. It also launches Ignition interpreter which is quiet efficient for all the small and big devices like servers or IOT devices etc that varies on memory spectrum. Due to such low memory footprint it delivers fast startup of an application. We can study benchmarks in following link : https://goo.gl/B15xB2

With two powerful updates, the v8 team is also working on Orinoco, which is a garbage collector that works on mechanism of parallel and concurrent compacting.

Such a high performance with promising results was the reason to push the node 8(LTS) launch date from may 2018 to october 2018. Currently we are using node 8 with a non-LTS version. It provides clean replace for users using node v4.x.x and above with no broken library. The version 8 also has various inbuilt features like buffer improvements and inbuilt promisify methods etc. We can study them in following link : https://goo.gl/kMySCS

With the advent of the web, the traditional JavaScript was intended to add simple functionality and minimal runtime in the browser. Thus, JavaScript was kept as a single-threaded scripting language. Now, just to get a brief idea regarding single-threaded model, let's consider the following diagram:

A single-threaded model creates a single Callstack in an execution context. In the preceding code, when the function getData() is invoked, the function is pushed in the stack for execution sequentially.

In the context of Node.js, JavaScript is the base scripting language, hence, Node.js is single-threaded. You might be asking, how does a single-threaded model help? Typical PHP, ASP.NET, Ruby, or Java-based servers follow a model where each client request results in the instantiation of a new thread or even a process.

When it comes to Node.js, requests are run on the same thread with shared resources. A question that is often asked is, what will be the advantage of using such a model? To understand this, we should understand the problem that Node.js tries to resolve. It tries to do asynchronous processing on a single thread to provide more performance and scalability for applications that are supposed to handle too much web traffic. Imagine web applications that handle millions of concurrent requests; if the server makes a new thread for handling each request that comes in, it will consume a lot of resources and we will end up trying to add more and more servers to increase the scalability of the application.

The single-threaded, asynchronous processing model has its advantage in the previous context, and you can process much more concurrent requests with fewer server-side resources. However, there is a downside to this approach; Node (by default) will not utilize the number of CPU cores available on the server it is running on, without using extra modules like pm2.

One of the most powerful features of Node.js is that it is both event-driven and asynchronous. So, how does an asynchronous model work? Imagine you have a block of code and at some n^th line you have an operation that is time consuming. What happens to the lines that follow the n^th line while this code gets executed? In normal synchronous programming models, the lines that follow the n^th line will have to wait until the operation at that line completes. An asynchronous model handles this case differently.

Let us visualize this scenario with the help of the following code and diagram:

In the preceding case, the setTimeout() method is provided by JavaScript (Node.js) API. Hence, this method is recognized as synchronous and is executed in a different execution context. According to functionality to setTimeout() , it executes the callback function after a specified duration, in our case after three seconds.

Further, the current execution is never blocked for a process to complete. When Node.js API determines that the completion of an event has been fired, it will execute your callback function at that moment.

In a typical synchronous programming language, executing the preceding code will yield the following output:

Writing applications with Node.js is really enjoyable when you realize the sheer wealth of information and tools at your disposal! Using Node.js's built-in package manager, npm, you can find literally tens of thousands of modules that can be installed and used within your application with just a few keystrokes! One of the biggest reasons for the success of Node.js is npm, which is one of the best package managers out there, with a very minute learning curve. If this is the first ever package manager that you are getting exposed to, you should consider yourself lucky!

On a regular month, npm handles more than a billion downloads, and it has around 150,000 packages currently available for you to download. You can view the library of available modules by visiting www.npmjs.com. Downloading and installing any module within your application is as simple as executing the following command:

npm install package 

Have you written a module that you want to share with the world? You can package it up using npm and upload it to the public registry at www.npmjs.org just as easily! If you are not sure how a module you installed works, the source code is right there in your project's node_modules/ folder waiting to be explored!

While you develop web applications, you will always end up doing the validations for your UI, both at the client and server sides, as the client-side validations are required for better UI experience and server-side validations are needed for better security of the app. Think about two different languages in action: you will have the same logic implemented in both the server and client sides. With Node.js, you can think of sharing the common function between server and client, reducing the code duplication to a large extent.

Ever worked on optimizing the load time for client-side components of your Single-Page Application (SPA) loaded from template engines such as Underscore? You would end up thinking about a way we could share the rendering of templates in both server and client at the same time; some call it hybrid templating.

Node.js resolves the context of duplication of client templates better than any other server-side technologies, just because we can use the same JS templating framework and the templates both at server and client.

If you are taking this point lightly, the problem it resolves is not just the issue of reusing validations or templates on the server and client. Think about an SPA being built; you will need to implement the subsets of server-side models in the client-side MV* framework also. Now, think about the templates, models, and controller subsets being shared on both client and server. We are solving a higher scenario of code redundancy.

Node.js is not just to write JavaScript in the server-side. Yes, we have discussed this point earlier. Node.js sets up the environment for the JavaScript code to work anywhere it can be installed. It can be a powerful solution to create command-line tools, as well as fully featured, locally run applications that have nothing to do with the web or a browser. Grunt.js is a great example of a Node-powered command-line tool that many web developers use daily to automate tasks such as build processes, compiling CoffeeScript, launching Node.js servers, running tests, and more.

In addition to command-line tools, Node.js is increasingly popular among the hardware crowd with the Node.js bots movement. Johnny-Five and Cylon.js are two popular Node.js libraries that exist to provide a framework to work with robotics. Just search on YouTube for Node.js robots and you will see a lot of examples. Also, there is a chance that you might be using a text editor developed on Node.js. GitHub's open source editor named Atom, which is hugely popular, is an example.

One of the important reasons behind the origin of Node.js was to support real-time web applications. Node.js has a couple of frameworks built for real-time web applications which are hugely popular: Socket.io and Sock.JS. These frameworks make it very simple to build instant, collaboration-based applications such as Google Drive and Mozilla's together.js. Before the introduction of WebSockets in the modern browsers, this was achieved via long polling, which was not a great solution for real-time experience. While WebSockets is a feature that is only supported in modern browsers, Socket.io acts as a framework, which also features seamless fallback implementations for legacy browsers.

In addition to the powerful non-blocking asynchronous nature of Node.js, it also has robust networking and filesystem tools available via its core modules. With Node.js's networking modules, you can create server and client applications that accept network connections and communicate via streams and pipes. Node contains a module named as fs or filesystem which is totally responsible for all kind of read write operations performed on files. It also takes an advantage of streaming feature of node to perform those operations.

Dividing the app with respect to a functionality unit is called a microservice. Each microservice becomes the self contained unit of deployment. Node.js is based on the common JS modules pattern which provides modularity in structure of an application. Such a pattern is used to create the microservices. With the increase of functionality, the number of microservices increases. To manage those services, the Node.js ecosystem provides powerful libraries like pm2. Therefore, it enables the elements of an application to be updated and scaled separately.

With the advent of Internet of things (IoT), the Node.JS ecosystem provides amazing library support for various devices like sensors, beacons, wearables, and so on. Node.js is considered as an ideal technology for managing the request made by those devices via its powerful backbone of streams and non-blocking I/O. Popular IoT board variants like Arduino, Raspberry Pi, and so on, have more than 300 Node.js packages. The developers building data-intensive, real-time applications often find Node.js as a natural fit.