Node.js has become a very popular language, so to speak. It's not actually a language, it's a wraparound language, like JavaScript, or ECMAScript. JavaScript was developed for the browser and it is actually small by definition. Then, browsers created a layer of access to the page elements and events, called DOM. That's one of the reasons why people hate the language so much. Node.js takes only the base language and adds an API so that developers have access to I/O, namely, the filesystem and network.

Ryan Dahl started developing Node.js back in 2009. He felt the need for a performant and less blocking program than the ones that were available. Node.js used Google's V8 JavaScript engine from the beginning and was first introduced at the JSConf in Berlin in 2009.

Looking just at the language, it's actually a sound and small, functional, object-oriented, prototype-based language. Everything is an object or inherits from it. Even numbers and functions inherit from an object. The good parts are as follows:

• Functions are first-class objects
• Functions and block-scoped variables
• Closures and anonymous functions
• Loose typing (can be seen as a bad aspect)

Node.js introduced JavaScript to a group of API modules that enable developers to access the filesystem, run and manage processes, and communicate over the network. Since it was first designed to replace a traditional web server, it also has HTTP and HTTPS modules to perform the roles of the client or server. Some other modules exist around these ones, which can be built as separate modules from the core (like DNS or URL), but live and are maintained inside the core.

At first, Node.js was very unstable, and not only the code's stability, but also the API's stability. Methods could change between versions dramatically. Modules got deprecated and replaced by others rapidly (search for the sys module for more information). Only brave developers would use it in production.

By the time it hit version 0.8, it became more reliable and the API had been stabilized. Large companies started supporting it and the community grew. Although there was a fork in 2014 because of internal conflicts, the community survived and the two code trees merged back in 2015:

Because of its use of Google's V8, and because it has a small and stable API, it's very fast and reliable. The reason for having a small API is that one of the guidelines of the community is to only have core functionality in the core API since everything else should go into a module. This has also become a major advantage of Node.js. It has a huge community with hundreds of thousands of modules available.

If you stop and think about it, this is the microservices approach – having separate modules to do one job and one job only, and do it well. You can easily find good, stable, and mature modules for specific needs, which are used by thousands of developers. These mature modules are all easy to deploy and have test suites to ensure they keep stable and functional.

But Node.js is not only about the modules. JavaScript has also evolved in the last couple of years and Google's V8 has always been an early adopter, so Node.js developers get access to the latest new features. Some of them have given developers new ways of simplifying code and removing some of the so-called callback hell.

Node.js's Long Term Support (LTS) version already has stable support for many new language features. Let's see some of them and how they're useful.