rerender-derived-state

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

Skills
Web development
0

What it does and how to use it

A skill that teaches Claude Code to do web development tasks well. It is packaged knowledge the model uses whenever it is relevant.

Install the skill (command above).
In Claude Code, describe what you need - the skill turns on by itself when the context fits.
No commands to memorize: you talk in plain language and the skill does the rest.

Install (Claude Code)

mkdir -p .claude/skills/rerender-derived-state && curl -fsSL https://doutorai.pt/data/lib/skills__rerender-derived-state.md -o .claude/skills/rerender-derived-state/SKILL.md

Paste this command into the terminal, in your project folder, and the component installs automatically.

Content

---
title: Subscribe to Derived State
impact: MEDIUM
impactDescription: reduces re-render frequency
tags: 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):**

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

**Correct (re-renders only when boolean changes):**

```tsx
function Sidebar(

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