parallel‑worker is a tiny library that creates a Web Worker (in the browser) or a spawned Node.js process and lets you communicate with it through a simple message channel. It supports a synchronous “function mode” for running a single function and returning its result (or promise), as well as an async mode for bidirectional messaging, with optional stdout/stderr streams in Node. The package targets developers who need lightweight parallel execution in both browser and Node environments without heavy tooling.