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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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#event loop

8 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

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

Microtask vs Macrotask in JavaScript — With Node.js vs Browser Notes

Understand microtasks and macrotasks across browsers and Node.js, including process.nextTick, setImmediate, and event loop phases.

Sep 20, 20253 min read

Related topics

#javascript#async#promises#microtask#await#browser#concurrency#diagram