80 lines
4.0 KiB
Markdown
80 lines
4.0 KiB
Markdown
---
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name: gsap-performance
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description: Official GSAP skill for performance — prefer transforms, avoid layout thrashing, will-change, batching. Use when optimizing GSAP animations, reducing jank, or when the user asks about animation performance, FPS, or smooth 60fps.
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license: MIT
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---
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# GSAP Performance
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## When to Use This Skill
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Apply when optimizing GSAP animations for smooth 60fps, reducing layout/paint cost, or when the user asks about performance, jank, or best practices for fast animations.
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**Related skills:** Build animations with **gsap-core** (transforms, autoAlpha) and **gsap-timeline**; for ScrollTrigger performance see **gsap-scrolltrigger**.
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## Prefer Transform and Opacity
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Animating **transform** (`x`, `y`, `scaleX`, `scaleY`, `rotation`, `rotationX`, `rotationY`, `skewX`, `skewY`) and **opacity** keeps work on the compositor and avoids layout and most paint. Avoid animating layout-heavy properties when a transform can achieve the same effect.
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- ✅ Prefer: **x**, **y**, **scale**, **rotation**, **opacity**.
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- ❌ Avoid when possible: **width**, **height**, **top**, **left**, **margin**, **padding** (they trigger layout and can cause jank).
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GSAP’s **x** and **y** use transforms (translate) by default; use them instead of **left**/**top** for movement.
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## will-change
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Use **will-change** in CSS on elements that will animate. It hints the browser to promote the layer.
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```css
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will-change: transform;
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```
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## Batch Reads and Writes
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GSAP batches updates internally. When mixing GSAP with direct DOM reads/writes or layout-dependent code, avoid interleaving reads and writes in a way that causes repeated layout thrashing. Prefer doing all reads first, then all writes (or let GSAP handle the writes in one go).
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## Many Elements (Stagger, Lists)
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- Use **stagger** instead of many separate tweens with manual delays when the animation is the same; it’s more efficient.
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- For long lists, consider **virtualization** or animating only visible items; avoid creating hundreds of simultaneous tweens if it causes jank.
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- Reuse timelines where possible; avoid creating new timelines every frame.
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## Frequently updated properties (e.g. mouse followers)
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Prefer **gsap.quickTo()** for properties that are updated often (e.g. mouse-follower x/y). It reuses a single tween instead of creating new tweens on each update.
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```javascript
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let xTo = gsap.quickTo("#id", "x", { duration: 0.4, ease: "power3" }),
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yTo = gsap.quickTo("#id", "y", { duration: 0.4, ease: "power3" });
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document.querySelector("#container").addEventListener("mousemove", (e) => {
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xTo(e.pageX);
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yTo(e.pageY);
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});
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```
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## ScrollTrigger and Performance
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- **pin: true** promotes the pinned element; pin only what’s needed.
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- **scrub** with a small value (e.g. `scrub: 1`) can reduce work during scroll; test on low-end devices.
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- Call **ScrollTrigger.refresh()** only when layout actually changes (e.g. after content load), not on every resize; debounce when possible.
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## Reduce Simultaneous Work
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- Pause or kill off-screen or inactive animations when they’re not visible (e.g. when the user navigates away).
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- Avoid animating huge numbers of properties on many elements at once; simplify or sequence if needed.
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## Best practices
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- ✅ Animate **transform** and **opacity**; use **will-change** in CSS only on elements that animate.
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- ✅ Use **stagger** instead of many separate tweens with manual delays when the animation is the same.
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- ✅ Use **gsap.quickTo()** for frequently updated properties (e.g. mouse followers).
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- ✅ Clean up or kill off-screen animations; call **ScrollTrigger.refresh()** when layout changes, debounced when possible.
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## Do Not
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- ❌ Animate **width**/ **height**/ **top**/ **left** for movement when **x**/ **y**/ **scale** can achieve the same look.
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- ❌ Set **will-change** or **force3D** on every element “just in case”; use for elements that are actually animating.
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- ❌ Create hundreds of overlapping tweens or ScrollTriggers without testing on low-end devices.
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- ❌ Ignore cleanup; stray tweens and ScrollTriggers keep running and can hurt performance and correctness.
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