Awesome JS Tooling not in JS

A curated list of JavaScript tooling not written in JavaScript

Bundlers

esbuild - JavaScript bundler in Go.
Parcel - Web application bundler, with its JavaScript transformer written in Rust on top of swc (source).
Bun - JS, TS, JSX bundler, JS and CSS transpiler, dev server and JS runtime environment, written in Zig.
Turbopack - incremental bundler optimized for JavaScript and TypeScript, written in Rust.
Rspack – A fast web bundler (drop-in replacement for Webpack), written in Rust.

swc - TypeScript/JavaScript compiler in Rust.
Relay - JavaScript framework for building data-driven React applications, compiler in Rust.
Paperclip - Presentational component compiler in Rust + WASM.
Closure Compiler - in Java.

Boa - Embeddable and experimental Javascript engine, written in Rust.
Goja - ECMAScript/JavaScript engine, written in Go .
Hermes - JavaScript engine optimized for React Native, written in C++.
V8 - High-performance JavaScript and WebAssembly engine, written in C++.
JavaScriptCore – JavaScript engine for Swift, Objective-C, and C-based apps, written in C++.

dprint - Pluggable and configurable code formatting platform written in Rust; supports several languages such as JavaScript/TypeScript.

Deno Lint
Flow - Static type checker for JavaScript, written in OCaml.
quick-lint-js - Written in C++.
RSLint - Extremely fast JavaScript and TypeScript linter, written in Rust. (WIP)

If you can think of a more appropriate category for the items below, PRs welcome!

Fast Node Manager (fnm) - Node.js version manager, written in Rust.
Volt - JavaScript Package Manager, written in Rust.
Volta - JavaScript Tool Manager, written in Rust.
es-module-lexer - JavaScript module syntax lexer, written in C.
npm-dep-check-rust - Find unused dependencies in Node.js applications, written in Rust.
Rome - Linter, compiler, bundler, and more for JavaScript, TypeScript, JSON, HTML, Markdown, and CSS, 🚧 currently being re-written in Rust (source).
Wrangler - CLI tool to develop Clouflare Workers, written in Rust.
Turborepo - The high-performance build system for JavaScript & TypeScript codebases, written in Go, 🚧 currently being migrated to Rust (source).
Blueboat – all-in-one, multi-tenant serverless JavaScript runtime, written in Rust.
Proto – A multi-language version and dependency manager, written in Rust.

Contributions welcome! Read the contribution guidelines first.