Claude Code Guide（zebbern）

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"} />
}