The Deno Handbook: A Concise Introduction to Deno

What is Deno? If you are familiar with Node.js, the popular server-side JavaScript ecosystem, then Deno is just like Node. Except deeply improved in many ways. After you use Deno and learn to appreciate its features, Node.js will look like something old. Especially because the Node.js API is callback based, as it was written way before promises and async/await. There’s no change in place for that in Node, as such a change would be monumental, so we’re stuck to callbacks or to promisifying API calls.

Node.js is awesome and will continue to be the de facto standard in the JavaScript world. But I think we’ll gradually see Deno more adopted because of its first-class TypeScript support and modern standard library. Deno can afford to have everything written with modern technologies, since there’s no backward compatibility to maintain. Of course there’s no guarantee that in a decade the same will happen to Deno and a new technology will emerge, but this is the reality at the moment.

Let’s start from a quick list of the features I like the most about Deno:

• It is based on modern features of the JavaScript language
• It has an extensive standard library
• It has TypeScript at its core, which brings a huge advantage in many different ways, including a first-class TypeScript support (you don’t have to separately compile TypeScript, it’s automatically done by Deno)
• It embraces ES modules
• It has no package manager
• It has a first-class await
• It as a built-in testing facility
• It aims to be browser-compatible as much as it can, for example by providing a built-in fetch and the global window object