Tell us about list virtualization — what is this feature and why was react-window used instead of React Fiber?

List virtualization is a technique for optimizing the rendering of long lists in an interface. Instead of rendering all list items at once (which can significantly slow down performance and consume a lot of memory), only the items visible to the user at the moment are rendered (plus a small buffer at the top and bottom).

This allows for a significant increase in application performance and responsiveness.

Why react-window and not React Fiber?

• React Fiber is React's architecture for efficient UI updates and managing rendering priorities, but it does not itself solve the problem of rendering very long lists.
• react-window is a specialized library that implements list virtualization, specifically optimizing this task.

In other words, React Fiber improves the overall performance of React applications, while react-window addresses the specific performance issue when working with large lists by minimizing the number of DOM elements rendered at the same time.

Example of using react-window:

import { FixedSizeList as List } from 'react-window';

const Row = ({ index, style }) => (
  <div style={style}>Item #{index}</div>
);

<List
  height={150}
  itemCount={1000}
  itemSize={35}
  width={300}
>
  {Row}
</List>

Here, only visible elements are rendered, which saves resources and speeds up the interface.