Meet Bun, a Speedy New JavaScript Runtime - Slashdot

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Bun is "a modern JavaScript runtime like Node or Deno," according to its newly-launched web site, "built from scratch to focus on three main things."

- Start fast (it has the edge in mind).
- New levels of performance (extending JavaScriptCore, the engine).
- Being a great and complete tool (bundler, transpiler, package manager).

Bun is designed as a drop-in replacement for your current JavaScript & TypeScript apps or scripts — on your local computer, server or on the edge. Bun natively implements hundreds of Node.js and Web APIs, including ~90% of Node-API functions (native modules), fs, path, Buffer and more. [And Bun also implements Node.js' module resolution algorithm, so you can use npm packages in bun.js]

The goal of Bun is to run most of the world's JavaScript outside of browsers, bringing performance and complexity enhancements to your future infrastructure, as well as developer productivity through better, simpler tooling.... Why is Bun fast? An enormous amount of time spent profiling, benchmarking and optimizing things. The answer is different for every part of Bun, but one general theme: [it's written in Zig.] Zig's low-level control over memory and lack of hidden control flow makes it much simpler to write fast software.

An infographic on the site claims its server-side rendering of React is more than three times faster than Node or Deno. And Bun.js can even automatically load environment variables from .env files, according to the site.

No more require("dotenv").load()

Hackaday describes it as "a performant all-in-one approach," including "bundling, transpiling, module resolution, and a fantastic foreign-function interface." Many Javascript projects have a bundling and transpiling step that takes the source and packages it together in a more standard format. Typescript needs to be packaged into javascript, and modules need to be resolved. Bun bakes all this in. Typescript and JSX "just work." This dramatically simplifies many projects as much of the build infrastructure is part of Bun itself, lowering cognitive load when trying to understand a project... Some web-specific APIs, such as fetch and Websockets, are also built-in.
"What's even wilder is that Bun is written by one person, Jared Sumner," the article points out — adding that the all the code is available on GitHub under the MIT License ("excluding dependencies which have various licenses.")