The Deno runtime

Deno provides a set of functions that are included in the runtime as globals in the Deno namespace. The runtime APIs are documented at https://doc.deno.land/ and can be used to do the most elementary, low-level things.

Two types of functions are available on Deno without any imports: Web APIs and the Deno namespace. Whenever there's a behavior in Deno that also exists on the browser, Deno mimics the browser APIs – those are Web APIs. Since you come from the JavaScript world, you're probably familiar with most of them. We're speaking about functions such as fetch, addEventListener, setTimeout, and objects such as window, Event, console, among others.

Code written using Web APIs can be bundled and run in the browser with no transformations.

The other big part of the APIs exposed by the runtime lives inside a global namespace named Deno. You can use the REPL and the documentation, two of the things we explored in Chapter 2, The Toolchain...