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infinite-canvas/.agents/skills/vercel-react-best-practices/rules/rerender-derived-state.md
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HouYunFei fb79a15508 docs(vercel-react-best-practices): 添加 Vercel React 最佳实践规则文档
- 添加 sections 定义文件,包含性能优化各领域分类
- 添加规则模板文件,规范文档结构和标签定义
- 添加异步操作优化规则,包括防止瀑布流、并行化、延迟等待等
- 添加包大小优化规则,包括避免桶式导入、动态导入、预加载等
- 添加服务端性能优化规则,包括 API 路
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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'} />
}