Svelte Virtuallists

only renders the visible items.

svelte-virtuallists

Keep your page efficient and fast: only shows the visible items!

About • Features • Usage • Demos • Samples

About

Keep your tables and lists efficient and fast: only render the visible items, instead of displaying all your data in large lists.

This package is a merge of svelte-tiny-virtual-list and he-virtual-list, ported to Svelte 5. I spend many many hours to learn and build an improved version. Many thanks to the original authors.

Features

❺❺➎⓹⓹ Svelte 5+ only Build for Svelte 5+ in Typescript.
🚀 Performant Render millions of items, without breaking a sweat.
🛠 Configurable Customize width, heigh, position, style, content.
💠 Layout Control Headless, support fixed and variables sizing, along with vertical and horizontal lists and tables.
🧩 Programming Interface Set positions and properties, raises events on state mutation.
💼 Small Compact and dependency free – Only ~5kb when compressed.

Installation

npm i svelte-virtuallists

Usage

This component can be used two different ways:

🤖 As a scrollable listover a large number of items, optionally read incrementally.
🧠 As a fondation for more complex components - TreeViews and DataGrids.

Browser Support


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Examples

Demos

Samples

<script>
    import { VirtualList } from 'svelte-virtuallists';

    const data = ['A', 'B', 'C', 'D', 'E', 'F' /* ... */];
</script>

<VirtualList class='mystyle' style='width:100%;height=600px' items={data}>
    {#snippet vl_slot({ index, item })}
        <div>
            Row: #{index} Item: {item}
        </div>
    {/snippet}
</VirtualList>

Props

The component accepts the following properties

Property	Type	Required?	Description
items	`any[]`	✓	the model, the data for the items to display in the list.
isHorizontal	`boolean (false)`		Whether the list should scroll vertically or horizontally. One of `'vertical'` (default) or `'horizontal'`.
isDisabled	`boolean (false)`		When the component is disabled it renders as a regular list
isTable	`boolean (false)`		Whether the rendering should be a table layout
sizeCalculator	`(index: number, item:any) => number alias SizingCalculatorFn`		Not recommended, as the component will adjust to the css rendering. If you need to control the sizing programmatically, use a function that returns the size (height or width) of the rendered row or column. This function's output is used for scrollbar positioning and is passed to the vl_slot.
scrollToOffset	`number`(in pixels)		Can be used to control the scrollbar offset in pixel. scrollToIndex and scrollToOffset MUST not be used together.
scrollToIndex	`number`(item index)		Moves the scrollbar to display the given item (at index). Follows scroll behavior and alignment policies. scrollToIndex and scrollToOffset MUST not be used together.
scrollToAlignment	`string (AUTO)`		Used in combination with scrollToIndex and scrollToOffset. Use `'start'` to always align items to the top of the container and `'end'` to align them bottom. Use `'center`' to align them in the middle of the container. `'auto'` scrolls the least amount possible to ensure that the specified `scrollToIndex` item is fully visible.
scrollToBehaviour	`string (AUTO)`		Used in combination with scrollToIndex and scrollToOffset, controls the scrolling behaviour movement. One of: `'auto'`, `'smooth'` or `'instant'` (default).

Snippets

Property	Type	Required?	Description
vl_slot	`(index:number, item:any, size?:number) => SnippetResult`	✓	Snippet called to render every item, see description below. Typescript signature VLSlotSignature
header	`() => SnippetResult`		Useful in table mode to render the table header columns.
footer	`() => SnippetResult`		Useful in table mode to render any table footer.

For instance,

<VirtualList items={myModel} style="height:600px">
  {#snippet vl_slot({ index, item }: VLSlotSignature)}
    <div style="border: 1px solid rgb(204, 204, 204);">
      Index:{index} Content:{item.text}
    </div>
  {/snippet}
</VirtualList>

Events

Property	Type	Required?	Description
onAfterScroll	`{offset, event}`		Fired when the scrollbar changes position.
onVisibleRangeUpdate	`{start, end}`		Fired when the visible window is sliding to display new items

onAfterScroll

Accepts a function with the following signature (event):VLScrollEvent => void

export interface VLScrollEvent {
  // either the value of `wrapper.scrollTop` or `wrapper.scrollLeft`
  offset: number | string;
  // the original event
  event: Event;
}

onVisibleRangeUpdate

Accepts a function with the following signature (range):VLRangeEvent => void

export interface VLRangeEvent {
  // index of the first visible item
  start: number;
  // index of the last visible item
  end: number;
}

Contributing

Please read CODE OF CONDUCT and the CONTRIBUTION guide for more details.

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