Chapter 1: What is Deno?

Deno is a secure runtime for JavaScript and TypeScript. I'll guess that you are probably getting that excitement of experimenting with a new tool. You have worked with JavaScript or TypeScript and have at least heard of Node.js. Deno will feel like it has the right amount of novelty for you and, at the same time, has some things that will sound familiar for someone working in the ecosystem.

Before we start getting our hands dirty, we'll understand how Deno was created and its motivations. Doing that will help us learn and understand it better.

We'll be focusing on practical examples throughout this book. We'll be writing code and then rationalizing and explaining the underlying decisions we've made. If you come from a Node.js background, some of the concepts might sound familiar to you. We will also explain Deno and compare it with its ancestor, Node.js.

Once the fundamentals are in place, we'll dive into Deno and explore its runtime features by building small utilities and real-world applications.

Without Node, there would be no Deno. To understand the latter well, we can't ignore its 10+ year-old ancestor, which is what we'll look at in this chapter. We'll explain the reasons for its creation back in 2009 and the pain points that were detected after a decade of usage.

After that, we'll present Deno and the fundamental differences and challenges it proposes to solve. We'll have a look at its architecture, some principles and influences of the runtime, and the use cases where it shines.

After understanding how Deno came to life, we will explore its ecosystem, its standard library, and some use cases where Deno is instrumental.

Once you've read this chapter, you'll be aware of what Deno is and what it is not, why it is not the next version of Node.js, and what to think about when you're considering Deno for your next project.

In this chapter, we'll cover the following topics:

• A little history
• Why Deno?
• Architecture and technologies that support Deno
• Grasping Deno's limitations
• Exploring Deno's use cases

Let's get started!