For nine long years, Node.js reigned supreme as the king of server-side JavaScript runtimes. But in 2018, Ryan Dahl, the original creator of Node.js, decided to shake things up and introduced Deno. Then, in 2021, Bun entered the arena, promising to be a lightning-fast, drop-in replacement for Node.js. Now, we have three solid runtimes to choose from. You probably already know Node.js, so let's dive into Bun and Deno to help you decide which one might be right for you.

The following comparison is based on insights from the excellent video "Deno 2 vs Bun: Which Should You Choose?" by the team at Better Stack.

What are Deno and Bun?

Deno: An open-source runtime created to address various issues with Node.js, such as performance and developer experience. It's written in Rust and uses the V8 engine, similar to Node.js.

Bun: Also an open-source JavaScript runtime focused on performance and developer experience. However, it's built using WebKit's JavaScriptCore instead of the V8 engine, and it's written in Zig. It aims to be a faster drop-in replacement for Node.js.

What They Have in Common

Both Bun and Deno were created to address Node.js's limitations and focus on a better developer experience. Here's what they have in common:

Built-in TypeScript Support: No extra configuration needed. Just write your TypeScript code and run it.

JSX Support: Great for full-stack development and quickly creating APIs.

Web Standard APIs: Built on top of familiar APIs like Fetch and WebSockets, so your code works on the server and in the browser without extra libraries or polyfills.

NPM Compatibility: Both runtimes work with NPM packages out of the box.

Built-in Testing: Bun has a Jest-compatible test runner, and Deno comes ready to go without extra dependencies.

Deno's Unique Features

Security: Security is baked into its core. Unlike Node.js and Bun, where packages get full system access by default, Deno locks everything down. You need to explicitly allow file and network access.

Comprehensive TypeScript Standard Library: Eliminates the need for common external packages and utilities.

Developer Experience: You get linting and formatting built right in. Compiling your code into a binary is just one command.

JSR: An open-source, cross-runtime code registry that allows users to easily share modern JavaScript and TypeScript.

Bun's Unique Features

Speed: Claims four times faster startup than Node.js, thanks to its JavaScriptCore engine and Zig implementation.

Built-in SQLite Database: Natively implements a high-performance SQLite3 driver.

Fast Package Manager: You can drop this into any JavaScript project with a package.json to instantly speed up your development workflow.

Hot Reloading: When any module or file changes, Bun reruns the file for you.

Optimized Native APIs: Implements a subset of native APIs on the Bun global object and through a number of built-in modules.

Bun Shell: Facilitates shell scripting with JavaScript and TypeScript.

C Compiler: Experimental support for compiling and running native C with shared memory and near-zero cool overhead.

Performance

Both Bun and Deno generally outperform Node.js. Benchmarks vary by use case, but you're not going to go wrong with either of them if you consider Node.js to be the alternative. As highlighted by Better Stack, the competition between these runtimes ultimately benefits developers with faster and more efficient tools.

When to Choose Which

Choose Deno if: You value security and standardization, want a mature alternative to Node.js, and need built-in development tools. Particularly good for new projects without legacy requirements.

Choose Bun if: You want better performance than Node.js with minimal friction, or if you're working with something like SQLite.

Adoption

In 2023, Bun was more used than Deno, likely due to its ease of being a drop-in replacement, as noted in the Better Stack video.

Conclusion

Both Deno and Bun offer modern, capable platforms that build on Node.js's legacy while fixing many of its pain points. The JavaScript runtime landscape is more exciting than ever, and as Better Stack points out, the choice between them depends on your specific needs and priorities.