$ show koajs/koa
Koa is a lightweight, expressive HTTP middleware framework for Node.js, designed to provide a robust foundation for web applications and APIs. It leverages async/await to eliminate callback hell and offers a clean, stack-like middleware composition. The core library (~570 SLOC) includes essential HTTP utilities such as content negotiation, cookie handling, redirection, and error handling, but deliberately excludes routing and templating, leaving those to third-party middleware. The architecture centers around a Context object that encapsulates Node's req/res, with Request and Response abstractions providing convenient getters/setters. Koa v3 adds support for AsyncLocalStorage for per-request context, WHATWG Web API types (Blob, ReadableStream, Response) as response bodies, and improved security around host header parsing. The codebase is well-maintained, with active development, comprehensive test coverage, and modern Node.js practices.
The LLM identified 2 files worth highlighting for reuse:
Provides a clean, reusable wrapper around URLSearchParams for parsing and stringifying query strings. Handles arrays and nested objects gracefully, converting single-element arrays to plain values. This utility is isolated, has no internal dependencies, and can be extracted into any Node.js project needing query string manipulation without the overhead of full querystring libraries.
A robust function to detect if a value is a Node.js stream by checking for the presence of readable, pipe, read, destroy, and other stream-specific properties. It handles edge cases like null and non-objects. This is a self-contained utility that can be reused in any Node.js project that needs to differentiate streams from other types, avoiding reliance on instanceof which can fail with cross-realm streams.