caolan/async ? reverse-engineered prompt

Build me a JavaScript utility library for working with asynchronous code in both Node and the browser.

I want it to feel like the classic Async library, with simple helpers for running tasks in series or in parallel, limiting concurrency, looping over arrays and objects, mapping and filtering results, and handling Node style callbacks cleanly. It should also support modern async and await functions where it makes sense, while still working with older callback based code.

Please make it easy to import from a main entry file, include a browser friendly build, and add clear documentation with examples that show the most common use cases. I’d also like a solid test suite so the core helpers are reliable, plus the usual project files needed to publish and maintain it. If you need to check current best practices for packaging or browser support, look up the latest docs online first.