Flatlist getItemLayout usecase : <p>Why we use getItemLayout in flatlist ,how it help to improve performance of a flatlist .check the react-native docs but didn't find a satisfying answer. </p>

<pre><code>  getItemLayout={(data, index) =&gt; (
    {length: ITEM_HEIGHT, offset: ITEM_HEIGHT * index, index}
  )}
</code></pre>

<p>what is offset here ,what it does?</p>
