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):
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):
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