stl-kit

The gap

JavaScript ships with arrays, maps, and sets — and stops. The moment you need a priority queue or a doubly linked list, you either import a decade-old package with any sprinkled through its types, or you write one inline and test it never. Coming from C++'s STL, the absence felt like a missing limb.

stl-kit is my answer: production-grade, STL-style collections — doubly linked lists, priority queues — designed type-first. The generics aren't decoration over untyped internals; the type system is load-bearing, so misuse fails at compile time instead of in production.

Library engineering is different engineering

An application ships behavior; a library ships a contract. That changes everything: the API surface is designed before the implementation, every public signature is a promise you'll keep for years, and the test suite (Vitest) is less about coverage percentage and more about pinning the contract down so refactors can't quietly bend it.

The build pipeline (Tsup) emits clean ESM and CJS with real type declarations — the unglamorous plumbing that decides whether a library feels professional the moment someone runs npm install.