virtual-item.md

title	VirtualItem

The VirtualItem object represents a single item returned by the virtualizer. It contains information you need to render the item in the coordinate space within your virtualizer's scrollElement and other helpful properties/functions.

export interface VirtualItem {
  key: string | number | bigint
  index: number
  start: number
  end: number
  size: number
}

The following properties and methods are available on each VirtualItem object:

key

key: string | number | bigint

The unique key for the item. By default this is the item index, but should be configured via the getItemKey Virtualizer option.

index

index: number

The index of the item.

start

start: number

The starting pixel offset for the item. This is usually mapped to a css property or transform like top/left or translateX/translateY.

end

end: number

The ending pixel offset for the item. This value is not necessary for most layouts, but can be helpful so we've provided it anyway.

size

size: number

The size of the item. This is usually mapped to a css property like width/height. Before an item is measured with the VirtualItem.measureElement method, this will be the estimated size returned from your estimateSize virtualizer option. After an item is measured (if you choose to measure it at all), this value will be the number returned by your measureElement virtualizer option (which by default is configured to measure elements with getBoundingClientRect()).

lane

lane: number

The lane index of the item. Items are assigned to the shortest lane. Lane assignments are cached immediately based on the size estimated by estimateSize by default; use deferLaneAssignment: true to base assignments on measured sizes instead. In regular lists it will always be set to 0 but becomes useful for masonry layouts (see variable examples for more details).