What is Deno?

Deno is a modern runtime that lets you execute JavaScript and TypeScript code outside of a web browser. It was created by the original author of Node.js and includes built-in security, a standard library, and developer tools all in one package.

Let's break it down

  • Modern runtime: a program that can run code written in a language (like JavaScript) on your computer, using up-to-date design ideas.
  • JavaScript and TypeScript: two programming languages; JavaScript is the language of the web, and TypeScript is a version of JavaScript that adds optional typing to help catch errors.
  • Outside a web browser: you can run the code on a server, your laptop, or any computer, not just inside a web page.
  • Created by the original author of Node.js: Ryan Dahl, who first built Node, also built Deno, so it benefits from his experience.
  • Built-in security: Deno runs code in a sandbox and requires you to explicitly grant permissions (like file or network access).
  • Standard library: a collection of ready-made functions (for things like reading files or making HTTP requests) that come with Deno, so you don’t need extra packages for many common tasks.
  • Developer tools: Deno includes a formatter, linter, test runner, and bundler right out of the box.

Why does it matter?

Because Deno gives developers a safer, more streamlined way to write server-side code, especially if they already use TypeScript. Its all-in-one approach reduces the need to install and configure many separate tools, saving time and reducing bugs.

Where is it used?

  • Building lightweight REST APIs or GraphQL servers that run on cloud VMs or containers.
  • Writing serverless functions for platforms like AWS Lambda, Deno Deploy, or Cloudflare Workers.
  • Creating command-line utilities and scripts for automation, file processing, or DevOps tasks.
  • Prototyping edge-computing services where fast startup and built-in security are important.

Good things about it

  • Secure by default: code can’t access the file system, network, or environment variables unless you allow it.
  • First-class TypeScript support: no extra compilation step needed.
  • Single executable: one binary includes the runtime, standard library, and tools, simplifying installation.
  • Rich standard library: many common tasks are covered without third-party dependencies.
  • Built-in tooling: formatter, linter, test runner, and bundler are ready to use immediately.

Not-so-good things

  • Smaller ecosystem: fewer third-party modules compared to the massive npm registry for Node.js.
  • Learning curve for permission flags: developers must remember to grant the right permissions, which can be confusing at first.
  • Still relatively young: some libraries and frameworks are still catching up, and community support may be less mature.
  • Performance differences: in certain high-throughput scenarios, Deno may not match the raw speed of highly optimized Node.js setups.