If your application renders long lists of data (hundreds or thousands of rows), we recommended using a technique known as “windowing”. This technique only renders a small subset of your rows at any given time, and can dramatically reduce the time it takes to re-render the components as well as the number of DOM nodes created.

- React.js documentation

React Component that render only items in viewport

• Simple API like .map()
• Created for dynamic item height/width (if you don't know item size)
• Works perfectly with Flexbox (unlike other libraries with pisition: absolute)
• Supports scroll to index
• Supports initial index
• Supports vertical ↕ and horizontal ↔ lists️️
• Tiny (<2kb minified+gzipped)

Try 100k list demo

• Installation:

  npm install --save react-viewport-list

• Basic Usage:

  import { useRef } from 'react';
  import ViewportList from 'react-viewport-list';
  
  const ItemsList = ({ items }) => {
      const ref = useRef(null);
  
      return (
          <div className="scroll-container" ref={ref}>
              <ViewportList viewportRef={ref} items={items} itemMinSize={40} margin={8}>
                  {(item) => (
                      <div key={item.id} className="item">
                          {item.title}
                      </div>
                  )}
              </ViewportList>
          </div>
      );
  };
  
  export default ItemsList;

• scrollToIndex

  Params

  name	type	default	description
  index	number	-1	Item index for scroll
  alignToTop	boolean / ScrollIntoViewOptions	true	scrollIntoView second argument
  offset	number	0	Offset after scrollIntoView

  Usage

  import { useRef } from 'react';
  import ViewportList from 'react-viewport-list';
  
  const ItemsList = ({ items }) => {
      const ref = useRef(null);
      const listRef = useRef(null);
  
      return (
          <div className="scroll-container" ref={ref}>
              <ViewportList ref={listRef} viewportRef={ref} items={items} itemMinSize={40} margin={8}>
                  {(item) => (
                      <div key={item.id} className="item">
                          {item.title}
                      </div>
                  )}
              </ViewportList>
              <button className="up-button" onClick={() => listRef.current.scrollToIndex(0)} />
          </div>
      );
  };
  
  export default ItemsList;

If you have performance issues, you can add will-change: transform to a scroll container.

You should remember that in some situations will-change: transform can cause performance issues not fixed them.

.scroll-container {
    will-change: transform;
}

• margin

  You should use only margin-bottom (or margin-right for 'x' axis) for items, and provide it to ViewportList props. Don't use margin-top (or margin-left for 'x' axis)

  .item {
      margin-bottom: 8px;
  }

• Grouping

  ViewportList render Fragment with items in viewport

  import { useRef } from 'react';
  import ViewportList from 'react-viewport-list';
  
  const ItemsList = ({ keyItems, items }) => {
      const ref = useRef(null);
  
      return (
          <div className="scroll-container" ref={ref}>
              <span className="group-title">{'Key Items'}</span>
              <ViewportList viewportRef={ref} items={keyItems} itemMinSize={60} margin={8}>
                  {(item) => (
                      <div key={item.id} className="key-item">
                          {item.title}
                      </div>
                  )}
              </ViewportList>
              <span className="group-title">{'Items'}</span>
              <ViewportList viewportRef={ref} items={items} itemMinSize={40} margin={8}>
                  {(item) => (
                      <div key={item.id} className="item">
                          {item.title}
                      </div>
                  )}
              </ViewportList>
          </div>
      );
  };
  export default ItemsList;

• Sorting

  You can use React Sortable HOC

  import { useRef } from 'react';
  import { SortableContainer, SortableElement } from 'react-sortable-hoc';
  import ViewportList from 'react-viewport-list';
  
  const SortableList = SortableContainer(({ innerRef, ...rest }) => <div {...rest} ref={innerRef} />);
  
  const SortableItem = SortableElement((props) => <div {...props} />);
  
  const ItemsList = ({ items, onSortEnd }) => {
      const ref = useRef(null);
  
      return (
          <SortableList innerRef={ref} className="scroll-container" onSortEnd={onSortEnd}>
              <ViewportList viewportRef={ref} items={items} itemMinSize={40} margin={8}>
                  {(item, index) => (
                      <SortableItem key={index} index={index} className="item">
                          {item.title}
                      </SortableItem>
                  )}
              </ViewportList>
          </SortableList>
      );
  };
  
  export default ItemsList;