Initial commit — Singular Particular Space v1

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>
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2026-03-27 12:09:22 +02:00
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---
title: Minimize State Variables and Derive Values
impact: MEDIUM
impactDescription: fewer re-renders, less state drift
tags: state, derived-state, hooks, optimization
---
## Minimize State Variables and Derive Values
Use the fewest state variables possible. If a value can be computed from existing state or props, derive it during render instead of storing it in state. Redundant state causes unnecessary re-renders and can drift out of sync.
**Incorrect (redundant state):**
```tsx
function Cart({ items }: { items: Item[] }) {
const [total, setTotal] = useState(0)
const [itemCount, setItemCount] = useState(0)
useEffect(() => {
setTotal(items.reduce((sum, item) => sum + item.price, 0))
setItemCount(items.length)
}, [items])
return (
<View>
<Text>{itemCount} items</Text>
<Text>Total: ${total}</Text>
</View>
)
}
```
**Correct (derived values):**
```tsx
function Cart({ items }: { items: Item[] }) {
const total = items.reduce((sum, item) => sum + item.price, 0)
const itemCount = items.length
return (
<View>
<Text>{itemCount} items</Text>
<Text>Total: ${total}</Text>
</View>
)
}
```
**Another example:**
```tsx
// Incorrect: storing both firstName, lastName, AND fullName
const [firstName, setFirstName] = useState('')
const [lastName, setLastName] = useState('')
const [fullName, setFullName] = useState('')
// Correct: derive fullName
const [firstName, setFirstName] = useState('')
const [lastName, setLastName] = useState('')
const fullName = `${firstName} ${lastName}`
```
State should be the minimal source of truth. Everything else is derived.
Reference: [Choosing the State Structure](https://react.dev/learn/choosing-the-state-structure)