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⚡ Bolt: Optimize BackToTop scroll event listener #109

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⚡ Bolt: Optimize BackToTop scroll event listener #109

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c9a0c17
⚡ Bolt: Optimize BackToTop scroll event listener
google-labs-jules[bot] Mar 20, 2026
f142adb
⚡ Bolt: Fix formatting issues in BackToTop and .commitlintrc.yml
google-labs-jules[bot] Mar 20, 2026
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2 changes: 1 addition & 1 deletion .commitlintrc.yml
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
extends:
- '@commitlint/config-conventional'
- "@commitlint/config-conventional"
rules:
type-enum:
- 2
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23 changes: 20 additions & 3 deletions components/elements/BackToTop.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -5,12 +5,29 @@ export default function BackToTop({ target }: Readonly<{ target: string }>) {
const [hasScrolled, setHasScrolled] = useState(false);

useEffect(() => {
/*
* ⚡ Bolt Optimization:
* - Throttles scroll events using requestAnimationFrame to prevent main-thread blocking and excessive re-renders.
* - Uses passive event listener to allow the browser to perform smooth scrolling without waiting for JS execution.
* Expected impact: Significant reduction in CPU usage and jank during fast scrolling.
*/
const state = { isTicking: false, tickingId: 0 };

const onScroll = () => {
setHasScrolled(window.scrollY > 100);
if (!state.isTicking) {
state.tickingId = window.requestAnimationFrame(() => {
setHasScrolled(window.scrollY > 100);
state.isTicking = false;
});
state.isTicking = true;
}
};

window.addEventListener("scroll", onScroll);
return () => window.removeEventListener("scroll", onScroll);
window.addEventListener("scroll", onScroll, { passive: true });
return () => {
window.removeEventListener("scroll", onScroll);
window.cancelAnimationFrame(state.tickingId);
};
Comment on lines +14 to +30
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@gemini-code-assist gemini-code-assist Bot Mar 20, 2026

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medium

For improved readability and maintainability, I suggest a few refinements:

  • Extract Magic Number: The scroll threshold 100 is a magic number. Extracting it into a named constant like SCROLL_THRESHOLD_PX makes its purpose clear and simplifies future modifications.
  • Descriptive Naming: Renaming state to throttleState and tickingId to animationFrameId more accurately describes their roles within the throttling logic.

These changes make the implementation easier to understand at a glance.

    const SCROLL_THRESHOLD_PX = 100;
    const throttleState = { isTicking: false, animationFrameId: 0 };

    const onScroll = () => {
      if (!throttleState.isTicking) {
        throttleState.animationFrameId = window.requestAnimationFrame(() => {
          setHasScrolled(window.scrollY > SCROLL_THRESHOLD_PX);
          throttleState.isTicking = false;
        });
        throttleState.isTicking = true;
      }
    };

    window.addEventListener("scroll", onScroll, { passive: true });
    return () => {
      window.removeEventListener("scroll", onScroll);
      window.cancelAnimationFrame(throttleState.animationFrameId);
    };

}, []);

const handleClick = () => {
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