Why should you care?

Explains promise callback ordering vs setTimeout.

See it live — copy this example

Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.

queueMicrotask(() => console.log("micro"));
Promise.resolve().then(() => console.log("promise"));
console.log("sync");

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• Sync runs first, then all microtasks in order, then macrotasks like timers.

Practice next

1. Run sync / promise / queueMicrotask example.
2. Predict order then verify in console.
3. Compare with setTimeout(0) in same script.
4. Chain three .then calls and log each step number.
5. Schedule queueMicrotask inside another microtask and observe nesting order.

Remember

Promises use microtask queue Run before next macrotask Keep handlers fast

ScriptVerse state flush

A microtask queue flushes batched DOM updates after promise-based data normalization completes.

Outcome: Knowing microtask timing explains why UI sometimes updates before paint.