Virtualization in React means only rendering the visible part of a large list or grid, rather than rendering all the items at once.
This technique dramatically improves performance, especially when dealing with hundreds or thousands of items.

How it works:

• The list renders only the items currently visible within the viewport.
• As the user scrolls, React dynamically renders and removes elements based on visibility.
• This minimizes DOM nodes, memory usage, and improves scroll performance.

Popular libraries for virtualization:

Library	Features	Link
react-window	Lightweight, efficient, customizable	react-window on GitHub
react-virtualized	Feature-rich: tables, lists, grids, infinite loader	react-virtualized on GitHub
virtuoso	Easy to use, highly customizable, smooth scrolling	virtuoso on GitHub

Example using react-window:

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

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

const VirtualizedList = () => (
  <List
    height={400}
    itemCount={1000}
    itemSize={35}
    width={300}
  >
    {Row}
  </List>
);

Even if you have 1000+ items, only a small portion is rendered at any time!

Summary:
Virtualization is critical for smooth performance in large lists, and using libraries like react-window makes it easy.

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