A tiny but mighty list virtualization library, with zero dependencies 💪
About • Features • Installation • Usage • Examples • License
Instead of rendering all your data in a huge list, the virtual list component just renders the items that are visible, keeping your page nice and light.
This is heavily inspired by react-tiny-virtual-list and uses most of its code and functionality!
- Tiny & dependency free – Only ~5kb gzipped
- Render millions of items, without breaking a sweat
- Scroll to index or set the initial scroll offset
- Supports fixed or variable heights/widths
- Vertical or Horizontal lists
svelte-infinite-loadingcompatibility
If you're using this component in a Sapper application, make sure to install the package to
devDependencies!
More Details
With npm:
$ npm install svelte-tiny-virtual-listWith yarn:
$ yarn add svelte-tiny-virtual-listWith pnpm (recommended):
$ npm i -g pnpm
$ pnpm install svelte-tiny-virtual-listFrom CDN (via unpkg):
<!-- UMD -->
<script src="https://unpkg.com/svelte-tiny-virtual-list@^1/dist/svelte-tiny-virtual-list.js"></script>
<!-- ES Module -->
<script src="https://unpkg.com/svelte-tiny-virtual-list@^1/dist/svelte-tiny-virtual-list.mjs"></script><script>
import VirtualList from 'svelte-tiny-virtual-list';
const data = ['A', 'B', 'C', 'D', 'E', 'F', /* ... */];
</script>
<VirtualList
width="100%"
height={600}
itemCount={data.length}
itemSize={50}>
<div slot="item" let:index let:style {style}>
Letter: {data[index]}, Row: #{index}
</div>
</VirtualList>Also works pretty well with svelte-infinite-loading:
<script>
import VirtualList from 'svelte-tiny-virtual-list';
import InfiniteLoading from 'svelte-infinite-loading';
let data = ['A', 'B', 'C', 'D', 'E', 'F', /* ... */];
function infiniteHandler({ detail: { complete, error } }) {
try {
// Normally you'd make an http request here...
const newData = ['G', 'H', 'I', 'J', 'K', 'L', /* ... */];
data = [...data, ...newData];
complete();
} catch (e) {
error();
}
}
</script>
<VirtualList
width="100%"
height={600}
itemCount={data.length}
itemSize={50}>
<div slot="item" let:index let:style {style}>
Letter: {data[index]}, Row: #{index}
</div>
<div slot="footer">
<InfiniteLoading on:infinite={infiniteHandler} />
</div>
</VirtualList>| Property | Type | Required? | Description |
|---|---|---|---|
| width | number | string* |
✓ | Width of List. This property will determine the number of rendered items when scrollDirection is 'horizontal'. |
| height | number | string* |
✓ | Height of List. This property will determine the number of rendered items when scrollDirection is 'vertical'. |
| itemCount | number |
✓ | The number of items you want to render |
| itemSize | number | number[] | (index: number) => number |
✓ | Either a fixed height/width (depending on the scrollDirection), an array containing the heights of all the items in your list, or a function that returns the height of an item given its index: (index: number): number |
| scrollDirection | string |
Whether the list should scroll vertically or horizontally. One of 'vertical' (default) or 'horizontal'. |
|
| scrollOffset | number |
Can be used to control the scroll offset; Also useful for setting an initial scroll offset | |
| scrollToIndex | number |
Item index to scroll to (by forcefully scrolling if necessary) | |
| scrollToAlignment | string |
Used in combination with scrollToIndex, this prop controls the alignment of the scrolled to item. One of: 'start', 'center', 'end' or 'auto'. 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 |
Used in combination with scrollToIndex, this prop controls the behaviour of the scrolling. One of: 'auto', 'smooth' or 'instant' (default). |
|
| stickyIndices | number[] |
An array of indexes (eg. [0, 10, 25, 30]) to make certain items in the list sticky (position: sticky) |
|
| overscanCount | number |
Number of extra buffer items to render above/below the visible items. Tweaking this can help reduce scroll flickering on certain browsers/devices. | |
| estimatedItemSize | number |
Used to estimate the total size of the list before all of its items have actually been measured. The estimated total height is progressively adjusted as items are rendered. | |
| getKey | (index: number) => any |
Function that returns the key of an item in the list, which is used to uniquely identify an item. This is useful for dynamic data coming from a database or similar. By default, it's using the item's index. |
* height must be a number when scrollDirection is 'vertical'. Similarly, width must be a number if scrollDirection is 'horizontal'
item- Slot for each item- Props:
index: number- Item indexstyle: string- Item style, must be applied to the slot (look above for example)
- Props:
header- Slot for the elements that should appear at the top of the listfooter- Slot for the elements that should appear at the bottom of the list (e.g.InfiniteLoadingcomponent fromsvelte-infinite-loading)
afterScroll- Fired after handling the scroll eventdetailProps:event: ScrollEvent- The original scroll eventoffset: number- Either the value ofwrapper.scrollToporwrapper.scrollLeft
itemsUpdated- Fired when the visible items are updateddetailProps:start: number- Index of the first visible itemend: number- Index of the last visible item
recomputeSizes(startIndex: number)- This method force recomputes the item sizes after the specified index (these are normally cached).
VirtualList has no way of knowing when its underlying data has changed, since it only receives a itemSize property. If the itemSize is a number, this isn't an issue, as it can compare before and after values and automatically call recomputeSizes internally.
However, if you're passing a function to itemSize, that type of comparison is error prone. In that event, you'll need to call recomputeSizes manually to inform the VirtualList that the size of its items has changed.
<script>
import { onMount } from 'svelte';
import VirtualList from 'svelte-tiny-virtual-list';
const data = ['A', 'B', 'C', 'D', 'E', 'F', /* ... */];
let virtualList;
function handleClick() {
virtualList.recomputeSizes(0);
}
</script>
<button on:click={handleClick}>Recompute Sizes</button>
<VirtualList
bind:this={virtualList}
width="100%"
height={600}
itemCount={data.length}
itemSize={50}>
<div slot="item" let:index let:style {style}>
Letter: {data[index]}, Row: #{index}
</div>
</VirtualList>You can style the elements of the virtual list like this:
<script>
import VirtualList from 'svelte-tiny-virtual-list';
const data = ['A', 'B', 'C', 'D', 'E', 'F', /* ... */];
</script>
<div class="list">
<VirtualList
width="100%"
height={600}
itemCount={data.length}
itemSize={50}>
<div slot="item" let:index let:style {style}>
Letter: {data[index]}, Row: #{index}
</div>
</VirtualList>
</div>
<style>
.list :global(.virtual-list-wrapper) {
background-color: #0f0;
/* ... */
}
.list :global(.virtual-list-inner) {
background-color: #f00;
/* ... */
}
</style>- Basic setup
- Controlled props
- Hacker News using svelte-infinite-loading
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