f5792c40be
Pulled ALL skills from 15 source repositories: - anthropics/skills: 16 (docs, design, MCP, testing) - obra/superpowers: 14 (TDD, debugging, agents, planning) - coreyhaines31/marketingskills: 25 (marketing, CRO, SEO, growth) - better-auth/skills: 5 (auth patterns) - vercel-labs/agent-skills: 5 (React, design, Vercel) - antfu/skills: 16 (Vue, Vite, Vitest, pnpm, Turborepo) - Plus 13 individual skills from various repos Mosaic Stack is not limited to coding — the Orchestrator and subagents serve coding, business, design, marketing, writing, logistics, analysis, and more. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
83 lines
2.2 KiB
Markdown
83 lines
2.2 KiB
Markdown
---
|
|
title: Pass Primitives to List Items for Memoization
|
|
impact: HIGH
|
|
impactDescription: enables effective memo() comparison
|
|
tags: lists, performance, memo, primitives
|
|
---
|
|
|
|
## Pass Primitives to List Items for Memoization
|
|
|
|
When possible, pass only primitive values (strings, numbers, booleans) as props
|
|
to list item components. Primitives enable shallow comparison in `memo()` to
|
|
work correctly, skipping re-renders when values haven't changed.
|
|
|
|
**Incorrect (object prop requires deep comparison):**
|
|
|
|
```tsx
|
|
type User = { id: string; name: string; email: string; avatar: string }
|
|
|
|
const UserRow = memo(function UserRow({ user }: { user: User }) {
|
|
// memo() compares user by reference, not value
|
|
// If parent creates new user object, this re-renders even if data is same
|
|
return <Text>{user.name}</Text>
|
|
})
|
|
|
|
renderItem={({ item }) => <UserRow user={item} />}
|
|
```
|
|
|
|
This can still be optimized, but it is harder to memoize properly.
|
|
|
|
**Correct (primitive props enable shallow comparison):**
|
|
|
|
```tsx
|
|
const UserRow = memo(function UserRow({
|
|
id,
|
|
name,
|
|
email,
|
|
}: {
|
|
id: string
|
|
name: string
|
|
email: string
|
|
}) {
|
|
// memo() compares each primitive directly
|
|
// Re-renders only if id, name, or email actually changed
|
|
return <Text>{name}</Text>
|
|
})
|
|
|
|
renderItem={({ item }) => (
|
|
<UserRow id={item.id} name={item.name} email={item.email} />
|
|
)}
|
|
```
|
|
|
|
**Pass only what you need:**
|
|
|
|
```tsx
|
|
// Incorrect: passing entire item when you only need name
|
|
<UserRow user={item} />
|
|
|
|
// Correct: pass only the fields the component uses
|
|
<UserRow name={item.name} avatarUrl={item.avatar} />
|
|
```
|
|
|
|
**For callbacks, hoist or use item ID:**
|
|
|
|
```tsx
|
|
// Incorrect: inline function creates new reference
|
|
<UserRow name={item.name} onPress={() => handlePress(item.id)} />
|
|
|
|
// Correct: pass ID, handle in child
|
|
<UserRow id={item.id} name={item.name} />
|
|
|
|
const UserRow = memo(function UserRow({ id, name }: Props) {
|
|
const handlePress = useCallback(() => {
|
|
// use id here
|
|
}, [id])
|
|
return <Pressable onPress={handlePress}><Text>{name}</Text></Pressable>
|
|
})
|
|
```
|
|
|
|
Primitive props make memoization predictable and effective.
|
|
|
|
**Note:** If you have the React Compiler enabled, you do not need to use
|
|
`memo()` or `useCallback()`, but the object references still apply.
|