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aris/.claude/skills/vercel-react-best-practices/rules/rerender-derived-state.md
kenneth 331a2596fa Add Claude skills for React best practices and web design
- react-best-practices: Performance optimization patterns (client-side only)
- web-design-guidelines: UI review against Web Interface Guidelines

Co-authored-by: Ona <no-reply@ona.com>
2026-01-17 11:53:08 +00:00

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title, impact, impactDescription, tags
title impact impactDescription tags
Subscribe to Derived State MEDIUM reduces re-render frequency rerender, derived-state, media-query, optimization

Subscribe to Derived State

Subscribe to derived boolean state instead of continuous values to reduce re-render frequency.

Incorrect (re-renders on every pixel change):

function Sidebar() {
  const width = useWindowWidth()  // updates continuously
  const isMobile = width < 768
  return <nav className={isMobile ? 'mobile' : 'desktop'} />
}

Correct (re-renders only when boolean changes):

function Sidebar() {
  const isMobile = useMediaQuery('(max-width: 767px)')
  return <nav className={isMobile ? 'mobile' : 'desktop'} />
}