React Performance

Loops with Ionic Components​

When using loops with Ionic components, we recommend using React's key attribute. This allows React to re-render loop elements in an efficient way by only updating the content inside of the component rather than re-creating the component altogether.

By using key you can provide a stable identity for each loop element so React can track insertions and deletions within the iterator. Below is an example of how to use key:

MyComponent.tsx

importReact,{ useState }from'react';
import{IonContent,IonItem,IonLabel,IonPage}from'@ionic/react';

exportconstMyComponent:React.FC=()=>{
const[items, setItems]=useState([{ id:0, value:'Item 0'},{ id:1, value:'Item 1'},...]);

return(
<IonPage>
<IonContent>
{items.map(item =>{
return(
<IonItemkey={item.id}>
<IonLabel>{item.value}</IonLabel>
</IonItem>
)
})}
</IonContent>
</IonPage>
)
}

In this example, we have an array of objects called items. Each object contains a value and an id. Using the key attribute, we pass the item.id for each object. This id is used to provide a stable identity for each loop element.

For more information on how React renders lists using key see: https://reactjs.org/docs/lists-and-keys.html