Quick Features

Row, Column, and Grid virtualization
One single headless hook
Fixed, variable and dynamic measurement modes
Imperative scrollTo control for offset, indices and alignment
Custom scrolling function support (eg. smooth scroll)

Examples

Fixed Rows/Cols/Grid- CodeSandbox - Source
Variable Rows/Cols/Grid- CodeSandbox - Source
Dynamic Rows/Cols/Grid- CodeSandbox - Source
Smooth Scrolling - CodeSandbox - Source
Infinite Scrolling - CodeSandbox - Source

Documentation

Installation
Sample
API
- useVirtual
Contributors ✨

Installation

$ npm i --save react-virtual
# or
$ yarn add react-virtual

Why?

React Virtual's most distinguishing feature is that it's just one single custom hook instead of a set of components. In more trendy terms, this means that it is "headless", allowing you to control 100% all of the markup and styles, exactly how you want.

React Virtual supplies you with primitive utilities that allow you to build any range of virtualized experiences. One testament to this is that you can combine 2 instances of useVirtual onto the same markup to achieve a virtualized grid, where with other utilites, you would need to use a dedicated Grid-like component.

Sample

This is just a quick sample of what it looks like to use React Virtual. Please refer to the examples for more usage patterns.

function RowVirtualizerFixed() {
  const parentRef = React.useRef()

  const rowVirtualizer = useVirtual({
    size: 10000,
    parentRef,
    estimateSize: React.useCallback(() => 35, []),
  })

  return (
    <>
      <div
        ref={parentRef}
        className="List"
        style={{
          height: `150px`,
          width: `300px`,
          overflow: 'auto',
        }}
      >
        <div
          className="ListInner"
          style={{
            height: `${rowVirtualizer.totalSize}px`,
            width: '100%',
            position: 'relative',
          }}
        >
          {rowVirtualizer.virtualItems.map(virtualRow => (
            <div
              key={virtualRow.index}
              className={virtualRow.index % 2 ? 'ListItemOdd' : 'ListItemEven'}
              style={{
                position: 'absolute',
                top: 0,
                left: 0,
                width: '100%',
                height: `${virtualRow.size}px`,
                transform: `translateY(${virtualRow.start}px)`,
              }}
            >
              Row {virtualRow.index}
            </div>
          ))}
        </div>
      </div>
    </>
  )
}

API

`useVirtual`

const {
  virtualItems: [
    { index, start, size, end, measureRef },
    /* ... */
  ],
  totalSize,
  scrollToIndex,
  scrollToOffset,
} = useVirtual({
  size,
  parentRef,
  estimateSize,
  overscan,
  horizontal,
  scrollToFn,
  useObserver,
})

Options

size: Integer
- Required
- The total count of elements
parentRef: React.useRef(DOMElement)
- Required
- The parent element whose inner-content is scrollable
estimateSize: Function(index) => Integer
- Defaults to () => 50
- Required
- Must be memoized using React.useCallback()
- This function receives the index of each item and should return either:
  - A fixed size
  - A variable size per-item
  - A best-guess size (when using dynamic measurement rendering)
- When this function's memoization changes, the entire list is recalculated
overscan: Integer
- Defaults to 1
- The amount of items to load both behind and ahead of the current window range
horizontal: Boolean
- Defaults to false
- When true, this virtualizer will use width and scrollLeft instead of height and scrollTop to determine size and offset of virtualized items.
scrollToFn: Function(offset, defaultScrollToFn) => void 0
- Optional
- This function, if passed, is responsible for implementing the scrollTo logic for the parentRef which is used when methods like scrollToOffset and scrollToIndex are called.
- Eg. You can use this function to implement smooth scrolling by using the supplied offset and the defaultScrollToFn as seen in the sandbox's Smooth Scroll example.
useObserver: Function(parentRef) => ({ width: number; height: number })
- Optional
- This hook, if passed, is responsible for getting parentRef's dimensions
- Eg. You can use this hook to replace @reach/observe-rect that react-virtual uses by default with ResizeObserver API
  - Caution! Depending on your bundling target, you might need to add resize-observer-polyfill
paddingStart: Integer
- Defaults to 0
- The amount of padding in pixels to add to the start of the virtual list
paddingEnd: Integer
- Defaults to 0
- The amount of padding in pixels to add to the end of the virtual list
- onScrollElement: React.useRef(DOMElement)
- Optional
- Allows using a different element to bind the onScroll event to
scrollOffsetFn: Function(event?: Event) => number
- Optional
- This function, if passed, is called on scroll to get the scroll offest rather than using parentRef's width or height
keyExtractor: Function(index) => String | Integer
- Optional
- This function receives the index of each item and should return the item's unique ID.
- This function should be passed whenever dynamic measurement rendering is enabled and the size or order of items in the list changes.

Returns

virtualItems: Array<item>
- item: Object
  - index: Integer
    - The index of the item
  - start: Integer
    - The starting measurement of the item
    - Most commonly used for positioning elements
  - size: Integer
    - The static/variable or, if dynamically rendered, the measured size of the item
  - end: Integer
    - The ending measurement of the item
  - measureRef: React.useRef | Function(el: DOMElement) => void 0
    - The ref/function to place on the rendered element to enable dynamic measurement rendering
totalSize: Integer
- The total size of the entire virtualizer
- When using dynamic measurement refs, this number may change as items are measured after they are rendered.
scrollToIndex: Function(index: Integer, { align: String }) => void 0
- Call this function to scroll the top/left of the parentRef element to the start of the item located at the passed index.
- align: 'start' | 'center' | 'end' | 'auto'
  - Defaults to auto
  - start places the item at the top/left of the visible scroll area
  - center places the item in the center of the visible scroll area
  - end places the item at the bottom/right of the visible scroll area
  - auto brings the item into the visible scroll area either at the start or end, depending on which is closer. If the item is already in view, it is placed at the top/left of the visible scroll area.
scrollToOffset: Function(offsetInPixels: Integer, { align: String }) => void 0
- Call this function to scroll the top/left of the parentRef element to the passed pixel offset.
- align: 'start' | 'center' | 'end' | 'auto'
  - Defaults to start
  - start places the offset at the top/left of the visible scroll area
  - center places the offset in the center of the visible scroll area
  - end places the offset at the bottom/right of the visible scroll area
  - auto brings the offset into the visible scroll area either at the start or end, depending on which is closer. If the offset is already in view, it is placed at the top/left of the visible scroll area.

Contributors ✨

Thanks goes to these wonderful people (emoji key):

_{Tanner Linsley}
💻 🤔 💡 🚧 👀

This project follows the all-contributors specification. Contributions of any kind welcome!

kalley/react-virtual