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5chan/.claude/skills/vercel-react-best-practices/rules/rerender-simple-expression-in-memo.md
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Tommaso CasaburiandClaude Opus 4.6 189d1c2165 add .claude config folder with Claude-equivalent agent and hook settings
Mirrors .cursor and .codex structure with Claude model assignments:
- haiku for lighter tasks (translator, browser-check, profiler)
- sonnet for standard tasks (code-quality, plan-implementer, etc.)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-29 16:35:21 +07:00

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title, impact, impactDescription, tags
title impact impactDescription tags
Do not wrap a simple expression with a primitive result type in useMemo LOW-MEDIUM wasted computation on every render rerender, useMemo, optimization

Do not wrap a simple expression with a primitive result type in useMemo

When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in useMemo. Calling useMemo and comparing hook dependencies may consume more resources than the expression itself.

Incorrect:

function Header({ user, notifications }: Props) {
  const isLoading = useMemo(() => {
    return user.isLoading || notifications.isLoading
  }, [user.isLoading, notifications.isLoading])

  if (isLoading) return <Skeleton />
  // return some markup
}

Correct:

function Header({ user, notifications }: Props) {
  const isLoading = user.isLoading || notifications.isLoading

  if (isLoading) return <Skeleton />
  // return some markup
}