In the previous chapter, we learned about how HTML becomes the DOM and how to use JavaScript to query and manipulate the content of a page.

Before JavaScript, all pages were static. After Netscape introduced the scripting environment to its browser, developers started using it to create dynamic and responsive applications. The applications started to become more and more complex but the only place where JavaScript was running was inside the browser. Then, in 2009, Ryan Dahl, the original developer of Node.js, decided to create a way to run JavaScript on the server side, simplifying the web developer's life by allowing them to build applications without having to depend on other languages.

In this chapter, you will learn how Node.js works and how to use it to create scripts using JavaScript. You will learn about the basics of the Node.js core APIs, where to find their documentation, and how to use their read-eval-print loop (REPL) command line.

With the skills...

Node.js is an execution environment that runs on top of the V8 JavaScript engine. Its base premise is that it is asynchronous and event-driven. This means that all the blocking operations, such as reading data from a file, can be handled in the background while the other parts of the application continue to do their work. When the data has finished loading, an event is emitted and whoever was waiting for the data can now execute and do the work.

From its inception, Node.js was designed to serve as an efficient backend for web applications. Because of that, it was widely adopted by companies of all sizes and industry types. Trello, LinkedIn, PayPal, and NASA are some of the companies that use Node.js in multiple parts of their technology stack.

But what is an execution environment? An execution environment provides basic functionality, such as APIs, for a programmer to write applications. Think about the browser, for example – it has the DOM, objects such...

Node.js and JavaScript have a huge community and a very fast-paced development cycle. Because of this rapid development and its release cycles, it is very easy to become out of date (check Node.js's previous releases page for more information: https://nodejs.org/en/download/releases/).

Can you imagine working on a project that uses Node.js and is a few years old? By the time you come back to fix a bug, you will notice that the version you have installed can't run the code anymore because of some compatibility issues. Or, you will find that you can't change the code using your current version since what is running in production is a couple of years old and doesn't have async/await or some other lifesaving feature you use a lot in the most recent version.

That issue happens with all programming languages and development environments, but in Node.js, this is prominent because of the extremely fast release cycles.

To solve this, it...

When someone talks about Node Package Manager or npm for short, they can be referring to one or more of the following three things:

• A command-line application that manages packages for a Node.js application
• The repository where developers and companies publish their packages for others to use
• The website where people manage their profile and search for packages

Most programming languages offer at least one way for developers to share packages with each other: Java has Maven, C# has NuGet, Python has PIP, and so on. Node.js started to ship with its own package manager just a few months after its initial release.

Packages can include any type of code that developers think would be useful to others. And sometimes, they also include tools to aid developers in terms of local development.

As the packaged code needs to be shared, there needs to be a repository where all the packages are stored. And to publish their packages, authors...

In this chapter, we learned about what Node.js is and how its single-threaded, asynchronous, event-driven programming model can be used to build simple and efficient applications. We also learned about nvm and how to manage multiple versions of Node.js. Then, we studied npm and used external libraries in our Node.js applications. Finally, we learned what npm scripts are and some basic concepts related to them.

To help you understand what you learned about in this chapter, you can go to the npm repository, find some projects, and explore their code bases. The best way to learn about npm, Node.js, and the packages and libraries that exist out there is to explore other people's code and see what and how they are building and also what libraries they use.

In the next chapter, we will explore the Node.js APIs and learn how to use them to build a real web scraping application. In future chapters, you will learn how to use npm scripts and packages to improve the quality...