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.agents/skills/vercel-react-native-skills/rules/list-performance-callbacks.md

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+---
+title: Hoist callbacks to the root of lists
+impact: MEDIUM
+impactDescription: Fewer re-renders and faster lists
+tags: tag1, tag2
+---
+
+## List performance callbacks
+
+**Impact: HIGH (Fewer re-renders and faster lists)**
+
+When passing callback functions to list items, create a single instance of the
+callback at the root of the list. Items should then call it with a unique
+identifier.
+
+**Incorrect (creates a new callback on each render):**
+
+```typescript
+return (
+  <LegendList
+    renderItem={({ item }) => {
+      // bad: creates a new callback on each render
+      const onPress = () => handlePress(item.id)
+      return <Item key={item.id} item={item} onPress={onPress} />
+    }}
+  />
+)
+```
+
+**Correct (a single function instance passed to each item):**
+
+```typescript
+const onPress = useCallback(() => handlePress(item.id), [handlePress, item.id])
+
+return (
+  <LegendList
+    renderItem={({ item }) => (
+      <Item key={item.id} item={item} onPress={onPress} />
+    )}
+  />
+)
+```
+
+Reference: [Link to documentation or resource](https://example.com)