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Short, diagram-first posts on JavaScript, React & Next.js. Follow via RSS or the newsletter.

© 2026 Mohsen Fallahnejad

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#async

9 posts

queueMicrotask Explained: The Smallest Async Queue in JavaScript

What queueMicrotask does, how it differs from Promise.then, and how microtasks really work under the hood.

Dec 31, 20251 min read1

Why async/await Doesn’t Make JavaScript Code Parallel

Async/await feels like parallel code, but it isn’t. Here’s why JavaScript is still single-threaded and how async really works.

Dec 30, 20253 min read1

How Promise.all Works in a Single-Threaded JavaScript World

If JavaScript is single-threaded, how can Promise.all handle multiple requests at the same time? A deep dive into the event loop and async I/O.

Dec 30, 20252 min read1

Promise APIs Compared: all vs race vs any vs allSettled

A practical and conceptual comparison of Promise.all, Promise.race, Promise.any, and Promise.allSettled.

Dec 30, 20253 min read2

AbortController & AbortSignal

Everything you need to cancel async work in JS: fetch, streams, custom tasks, React patterns, Node notes, timeouts, races, and common pitfalls.

Sep 23, 20254 min read

JavaScript Promises Explained

A simple but deep dive into how Promises work in JavaScript and why they matter.

Sep 23, 20252 min read

JavaScript is Single-Threaded

Understand what it means when people say JS is single-threaded.

Sep 23, 20252 min read

JavaScript's Event Loop — Simple Guide (with SVG Timeline)

Event loop explained with a clean SVG timeline showing the actual execution order: Start → End → Promise → Timeout.

Sep 20, 20251 min read

Async vs Sync in JavaScript

Understand the difference between synchronous and asynchronous code in JavaScript with simple examples and analogies.

Sep 13, 20251 min read

Related topics

#javascript#event loop#promises#abortcontroller#abortsignal#await#basics#concurrency