The Scheduling Boundaries Behind Responsive UI
The article discusses the importance of scheduling boundaries in creating responsive user interfaces using JavaScript. It explains how long tasks can block the main thread, leading to unresponsive UIs, and emphasizes the need for cooperation in UI code. Different scheduling mechanisms like Promises, setTimeout, and requestAnimationFrame are outlined to manage rendering and improve responsiveness.
- ▪Long tasks can monopolize the main thread, causing the UI to become unresponsive.
- ▪Chaining promises does not create render opportunities, as the browser must drain the entire microtask queue before rendering.
- ▪Using setTimeout or requestAnimationFrame can introduce scheduling boundaries that allow the browser to render updates.
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| Original publisher | DEV.to (Top) |
| Canonical URL | https://dev.to/marshateo/the-scheduling-boundaries-behind-responsive-ui-2m56 |
| Publication time | Mon, 18 May 2026 05:35:33 +0000 |
| Retrieval time | 2026-05-18T06:04:56.103Z |
| Last seen | 2026-05-18T06:04:56.103Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | ebzViSEGTokh |
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| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
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| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
try { if(localStorage) { let currentUser = localStorage.getItem('current_user'); if (currentUser) { currentUser = JSON.parse(currentUser); if (currentUser.id === 3862667) { document.getElementById('article-show-container').classList.add('current-user-is-article-author'); } } } } catch (e) { console.error(e); } Marsha Teo Posted on May 18 • Originally published at marshateo.com The Scheduling Boundaries Behind Responsive UI #javascript #webdev This is the last article in a series on how JavaScript actually runs. You can read the full series here or on my website. We now know how the event loop and rendering pipeline behave. The browser: Runs a macrotask to completion. Drains all microtasks. Executes any scheduled requestAnimationFrame callbacks. Drains all microtasks.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at DEV.to (Top).
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