The answer
For CPU-intensive work that would block the main thread. Web Workers run on a separate thread, so the main thread stays responsive. setTimeout cannot solve blocking; it only defers it.
Alternatives to setTimeout in Modern JavaScript
When should you use Web Workers instead of setTimeout?
More FAQs in Alternatives to setTimeout in Modern JavaScript
requestAnimationFrame (animations), queueMicrotask (urgent work), requestIdleCallback (low-priority work), scheduler.postTask (prioritized scheduling), async/await (async flow), and Web Workers (heavy computation).
For animations and visual DOM updates. requestAnimationFrame syncs with the browser's refresh rate, runs before the next paint, and pauses when the tab is hidden.
A newer API for prioritized task scheduling. You can specify priorities: user-blocking, user-visible, or background. Use it when you need fine-grained control over task priority.
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