Advanced Execution in JS: Promises and Web Workers

This GitHub repo is the companion to ARTICLE.md: a short article plus runnable examples for Promises, Web Workers, Comlink, SharedArrayBuffer, workerpool, and Piscina.

Clone the repo, open an example folder, and run it while you read.

Examples

#	Project	What it shows	Runtime
01	examples/01-main-thread-freeze	Heavy loop wrapped in async still freezes the UI	Browser
02	examples/02-raw-web-worker	Same work via postMessage stays responsive	Browser
03	examples/03-comlink-worker	RPC-style API with Comlink (wrap / expose)	Browser
04	examples/04-shared-array-buffer	Shared memory + COOP/COEP headers	Browser
05	examples/05-workerpool	Job queue across a pool of workers	Browser
06	examples/06-piscina-node	Node.js worker_threads pool with Piscina	Node

Quick start

git clone git@github.com:mrajaeim/Advanced-JS-Execution.git
cd Advanced-JS-Execution

Each browser example uses Vite:

cd examples/02-raw-web-worker
npm install
npm run dev

Node example:

cd examples/06-piscina-node
npm install
npm start

Requirements

• Node.js 18+
• A modern Chromium-based browser for SharedArrayBuffer (example 04 needs cross-origin isolation; Vite already sets the headers)

Article

Read the full write-up: Why Promises Do Not Free Your UI (and When Web Workers Do)

Related

Call stack, microtasks/macrotasks, and the event loop: Why Your JavaScript Runs in the Wrong Order

License

MIT