---
title: "list performance callbacks"
description: "**Impact: HIGH (Fewer re-renders and faster lists)**"
type: skill
canonical_url: https://claudary.paisolsolutions.com/skills/list-performance-callbacks
source: "Claudary"
difficulty: intermediate
author: "Claude Code Knowledge Pack"
date: 2026-07-10T11:30:36.220Z
license: CC-BY-4.0
attribution: "list performance callbacks — Claudary (https://claudary.paisolsolutions.com/skills/list-performance-callbacks)"
---

# list performance callbacks
**Impact: HIGH (Fewer re-renders and faster lists)**

## Overview

---
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)

---

Source: [Claudary](https://claudary.paisolsolutions.com/skills/list-performance-callbacks) · https://claudary.paisolsolutions.com