JL Kruger
5422131782
Homepage (site/index.html): integration-v14 promoted, Writings section integrated with 33 pieces clustered by type (stories/essays/miscellany), Writings welcome lightbox, content frame at 98% opacity. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
30 lines
728 B
Markdown
30 lines
728 B
Markdown
---
|
|
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() {
|
|
const isMobile = useMediaQuery('(max-width: 767px)')
|
|
return <nav className={isMobile ? 'mobile' : 'desktop'} />
|
|
}
|
|
```
|