react-native

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Translated

Best practices for React Native and Expo applications. Covers list performance, animations with Reanimated, navigation, UI patterns, and monorepo configuration. Use when building, reviewing, or optimizing React Native / Expo apps.

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Sources-hiraoku/synapse-a2a

Added on2026-02-11

NPX Install

npx skill4agent add s-hiraoku/synapse-a2a react-native

SKILL.md Content

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React Native

Performance-first patterns for React Native and Expo, organized by impact.

Priority 1: List Performance (CRITICAL)

Lists are the #1 performance bottleneck in RN apps. Get these right first.

Use FlashList

Replace

FlatList

with

@shopify/flash-list

for large lists.

tsx

import { FlashList } from '@shopify/flash-list';

<FlashList
  data={items}
  renderItem={({ item }) => <ItemRow item={item} />}
  estimatedItemSize={80}
  keyExtractor={(item) => item.id}
/>

Memoize List Items

Every list item must be memoized.

tsx

const ItemRow = memo(function ItemRow({ item }: { item: Item }) {
  return (
    <View style={styles.row}>
      <Text>{item.title}</Text>
    </View>
  );
});

Stabilize Callbacks

Extract callbacks and avoid inline objects in list items.

tsx

// BAD: New function + new style object every render
<Pressable onPress={() => onSelect(item.id)} style={{ padding: 16 }}>

// GOOD: Stable references
const handlePress = useCallback(() => onSelect(item.id), [item.id, onSelect]);
<Pressable onPress={handlePress} style={styles.pressable}>

Optimize Images in Lists

Use

expo-image

with proper sizing and caching.

tsx

import { Image } from 'expo-image';

<Image
  source={{ uri: item.thumbnailUrl }}
  style={styles.thumbnail}
  contentFit="cover"
  placeholder={item.blurhash}
  transition={200}
  recyclingKey={item.id}
/>

Item Types for Heterogeneous Lists

Use

getItemType

to help FlashList reuse cells efficiently.

tsx

<FlashList
  data={mixedItems}
  renderItem={renderItem}
  getItemType={(item) => item.type} // 'header' | 'content' | 'ad'
  estimatedItemSize={100}
/>

Priority 2: Animation (HIGH)

GPU-Only Properties

Only animate

transform

and

opacity

. Everything else triggers layout.

tsx

import Animated, { useAnimatedStyle, withSpring } from 'react-native-reanimated';

const animatedStyle = useAnimatedStyle(() => ({
  transform: [{ scale: withSpring(isPressed.value ? 0.95 : 1) }],
  opacity: withSpring(isVisible.value ? 1 : 0),
}));

Derived Values

Use

useDerivedValue

for computed animations to avoid redundant calculations.

tsx

const progress = useSharedValue(0);
const rotation = useDerivedValue(() => `${progress.value * 360}deg`);

const animatedStyle = useAnimatedStyle(() => ({
  transform: [{ rotate: rotation.value }],
}));

Gesture Handling

Use

react-native-gesture-handler

for 60fps gesture tracking.

tsx

import { Gesture, GestureDetector } from 'react-native-gesture-handler';

const pan = Gesture.Pan()
  .onUpdate((e) => {
    translateX.value = e.translationX;
    translateY.value = e.translationY;
  })
  .onEnd(() => {
    translateX.value = withSpring(0);
    translateY.value = withSpring(0);
  });

// Use Gesture.Tap() instead of Pressable for animated press feedback
const tap = Gesture.Tap()
  .onBegin(() => { scale.value = withSpring(0.95); })
  .onFinalize(() => { scale.value = withSpring(1); });

Priority 3: Navigation (HIGH)

Native Navigators

Always prefer native stack and tabs over JS-based alternatives.

tsx

import { createNativeStackNavigator } from '@react-navigation/native-stack';
import { createBottomTabNavigator } from '@react-navigation/bottom-tabs';

// BAD: JS-based stack (slower transitions, no native gestures)
import { createStackNavigator } from '@react-navigation/stack';

// GOOD: Native stack (native transitions + gestures)
const Stack = createNativeStackNavigator();

Screen Options

Configure headers and animations natively.

tsx

<Stack.Screen
  name="Detail"
  component={DetailScreen}
  options={{
    headerLargeTitle: true,    // iOS large title
    animation: 'slide_from_right',
  }}
/>

Priority 4: UI Patterns (HIGH)

Safe Areas

Handle safe areas correctly for all device shapes.

tsx

import { SafeAreaView } from 'react-native-safe-area-context';

// For scrollable content
<SafeAreaView edges={['top']} style={{ flex: 1 }}>
  <ScrollView contentInsetAdjustmentBehavior="automatic">
    {children}
  </ScrollView>
</SafeAreaView>

Native Modals

Use native modal presentation instead of JS overlays.

tsx

<Stack.Screen
  name="Settings"
  component={SettingsScreen}
  options={{ presentation: 'modal' }}
/>

Native Menus

Use context menus instead of custom dropdown components.

tsx

import * as ContextMenu from 'zeego/context-menu';

<ContextMenu.Root>
  <ContextMenu.Trigger>
    <Pressable><Text>Options</Text></Pressable>
  </ContextMenu.Trigger>
  <ContextMenu.Content>
    <ContextMenu.Item key="edit" onSelect={handleEdit}>
      <ContextMenu.ItemTitle>Edit</ContextMenu.ItemTitle>
    </ContextMenu.Item>
    <ContextMenu.Item key="delete" onSelect={handleDelete} destructive>
      <ContextMenu.ItemTitle>Delete</ContextMenu.ItemTitle>
    </ContextMenu.Item>
  </ContextMenu.Content>
</ContextMenu.Root>

Pressable Over TouchableOpacity

tsx

// BAD: Legacy touch component
<TouchableOpacity onPress={onPress}>{children}</TouchableOpacity>

// GOOD: Modern Pressable with feedback
<Pressable
  onPress={onPress}
  style={({ pressed }) => [styles.button, pressed && styles.pressed]}
  android_ripple={{ color: 'rgba(0,0,0,0.1)' }}
>
  {children}
</Pressable>

Priority 5: State Management (MEDIUM)

Minimize Re-renders

Subscribe only to the state you need.

tsx

// BAD: Re-renders on any store change
const store = useStore();
return <Text>{store.user.name}</Text>;

// GOOD: Selector extracts only needed value
const name = useStore((s) => s.user.name);
return <Text>{name}</Text>;

React Compiler Compatibility

When using React Compiler with Reanimated:

tsx

// Destructure shared value functions for compiler compatibility
const { value } = useSharedValue(0);

// Use worklet directive for Reanimated callbacks
const animatedStyle = useAnimatedStyle(() => {
  'worklet';
  return { opacity: value };
});

Priority 6: Monorepo (MEDIUM)

Native Dependencies

Keep native dependencies in the app package, not shared packages.

packages/
  ui/              # Pure React components (no native deps)
  shared/          # Business logic, types
apps/
  mobile/          # Native deps (expo-image, reanimated) here

Single Dependency Versions

Enforce one version per dependency across the monorepo.

json

// Root package.json
{
  "resolutions": {
    "react-native": "0.76.x",
    "react-native-reanimated": "3.x"
  }
}

Quick Reference

Issue	Fix	Priority
Slow scrolling lists	FlashList + memoized items	CRITICAL
Inline objects in lists	Extract to StyleSheet	CRITICAL
Janky animations	Only transform/opacity	HIGH
JS-based navigation	Native stack/tabs	HIGH
Custom dropdown menus	Native context menus	HIGH
Full store subscription	Selectors	MEDIUM
Native deps in shared pkg	Move to app package	MEDIUM