virtua

A zero-config, fast and small (~3kB) virtual list (and grid) component for React, Vue, Solid and Svelte.

If you want to check the difference with the alternatives right away, see comparison section.

Motivation

This project is a challenge to rethink virtualization. The goals are...

• Zero-config virtualization: This library is designed to give the best performance without configuration. It also handles common hard things in the real world (dynamic size measurement, scroll position adjustment while reverse scrolling and imperative scrolling, iOS support, etc).
• Fast: Natural virtual scrolling needs optimization in many aspects (eliminate frame drops by reducing CPU usage and GC, reduce synchronous layout recalculation, reduce visual jumps on repaint, optimize with CSS, optimize for JIT, optimize for frameworks, etc). We are trying to combine the best of them.
• Small: Its bundle size should be small as much as possible to be friendly with modern web development. Currently each components are ~3kB gzipped and tree-shakeable.
• Flexible: Aiming to support many usecases - fixed size, dynamic size, horizontal scrolling, reverse scrolling, RTL, mobile, infinite scrolling, scroll restoration, DnD, keyboard navigation, sticky, placeholder and more. See live demo.
• Framework agnostic: React, Vue, Solid and Svelte are supported. We could support other frameworks in the future.

Demo

https://inokawa.github.io/virtua/

Install

npm install virtua

If you use this lib in legacy browsers which does not have ResizeObserver, you should use polyfill.

Getting started

React

react >= 16.14 is required.

If you use ESM and webpack 5, use react >= 18 to avoid Can't resolve react/jsx-runtime error.

Vertical scroll

import { VList } from "virtua";

// children
export const App = () => {
  return (
    <VList style={{ height: 800 }}>
      {Array.from({ length: 1000 }).map((_, i) => (
        <div
          key={i}
          style={{
            height: Math.floor(Math.random() * 10) * 10 + 10,
            borderBottom: "solid 1px gray",
            background: "white",
          }}
        >
          {i}
        </div>
      ))}
    </VList>
  );
};

// or render prop
export const App = () => {
  const items = Array.from({ length: 1000 }).map(
    () => Math.floor(Math.random() * 10) * 10 + 10,
  );
  return (
    <VList data={items} style={{ height: 800 }}>
      {(d, i) => (
        <div
          key={i}
          style={{
            height: d,
            borderBottom: "solid 1px gray",
            background: "white",
          }}
        >
          {i}
        </div>
      )}
    </VList>
  );
};

Horizontal scroll

import { VList } from "virtua";

export const App = () => {
  return (
    <VList style={{ height: 400 }} horizontal>
      {Array.from({ length: 1000 }).map((_, i) => (
        <div
          key={i}
          style={{
            width: Math.floor(Math.random() * 10) * 10 + 10,
            borderRight: "solid 1px gray",
            background: "white",
          }}
        >
          {i}
        </div>
      ))}
    </VList>
  );
};

Customization

VList is a recommended solution which works like a drop-in replacement of simple list built with scrollable div (or removed virtual-scroller element). For more complicated styling or markup, use Virtualizer.

import { Virtualizer } from "virtua";

export const App = () => {
  return (
    <div style={{ overflowY: "auto", overflowAnchor: "none", height: 800 }}>
      <div style={{ height: 40 }}>header</div>
      <Virtualizer startMargin={40}>
        {Array.from({ length: 1000 }).map((_, i) => (
          <div
            key={i}
            style={{
              height: Math.floor(Math.random() * 10) * 10 + 10,
              borderBottom: "solid 1px gray",
              background: "white",
            }}
          >
            {i}
          </div>
        ))}
      </Virtualizer>
    </div>
  );
};

Window scroll

import { WindowVirtualizer } from "virtua";

export const App = () => {
  return (
    <div style={{ padding: 200 }}>
      <WindowVirtualizer>
        {Array.from({ length: 1000 }).map((_, i) => (
          <div
            key={i}
            style={{
              height: Math.floor(Math.random() * 10) * 10 + 10,
              borderBottom: "solid 1px gray",
              background: "white",
            }}
          >
            {i}
          </div>
        ))}
      </WindowVirtualizer>
    </div>
  );
};

Vertical and horizontal scroll

import { experimental_VGrid as VGrid } from "virtua";

export const App = () => {
  return (
    <VGrid style={{ height: 800 }} row={1000} col={500}>
      {({ rowIndex, colIndex }) => (
        <div
          style={{
            width: ((colIndex % 3) + 1) * 100,
            background: "white",
            borderLeft: colIndex !== 0 ? "solid 1px gray" : undefined,
            borderTop: rowIndex !== 0 ? "solid 1px gray" : undefined,
          }}
        >
          {rowIndex} / {colIndex}
        </div>
      )}
    </VGrid>
  );
};

Vue

vue >= 3.2 is required.

<script setup>
import { VList } from "virtua/vue";

const sizes = [20, 40, 180, 77];
const data = Array.from({ length: 1000 }).map((_, i) => sizes[i % 4]);
</script>

<template>
  <VList :data="data" :style="{ height: '800px' }" #default="{ item, index }">
    <div
      :key="index"
      :style="{
        height: item + 'px',
        background: 'white',
        borderBottom: 'solid 1px #ccc',
      }"
    >
      {{ index }}
    </div>
  </VList>
</template>

Solid

solid-js >= 1.0 is required.

import { VList } from "virtua/solid";

export const App = () => {
  const sizes = [20, 40, 180, 77];
  const data = Array.from({ length: 1000 }).map((_, i) => sizes[i % 4]);

  return (
    <VList data={data} style={{ height: "800px" }}>
      {(d, i) => (
        <div
          style={{
            height: d + "px",
            "border-bottom": "solid 1px #ccc",
            background: "#fff",
          }}
        >
          {i()}
        </div>
      )}
    </VList>
  );
};

Svelte

svelte >= 5.0 is required.

<script lang="ts">
  import { VList } from "virtua/svelte";

  const sizes = [20, 40, 180, 77];

  const data = Array.from({ length: 1000 }).map((_, i) => sizes[i % 4] );
</script>

<VList {data} style="height: 100vh;" getKey={(_, i) => i}>
  {#snippet children(item, index)}
    <div
      style="
        height: {item}px;
        background: white;
        border-bottom: solid 1px #ccc;
      "
    >
      {index}
    </div>
  {/snippet}
</VList>

Other bindings

• vanilla-virtua: virtua for vanilla js

Documentation

• API reference
• Storybook examples for more usages
• DeepWiki

FAQs

Is there any way to improve performance further?

In complex usage, especially if you re-render frequently the parent of virtual scroller or the children are tons of items, children element creation can be a performance bottle neck. That's because creating React elements is fast enough but not free and new React element instances break some of memoization inside virtual scroller.

One solution is memoization with useMemo. You can use it to reduce computation and keep the elements' instance the same. And if you want to pass state from parent to the items, using context instead of props may be better because it doesn't break the memoization.

const elements = useMemo(
  () => tooLongArray.map((d) => <Component key={d.id} {...d} />),
  [tooLongArray],
);
const [position, setPosition] = useState(0);
return (
  <div>
    <div>position: {position}</div>
    <VList onScroll={(offset) => setPosition(offset)}>{elements}</VList>
  </div>
);

The other solution is using render prop as children to create elements lazily. It will effectively reduce cost on start up when you render many items (>1000). An important point is that newly created elements from render prop will disable optimization possible with cached element instances. We recommend using memoized function or component to reduce calculation and re-rendering during scrolling.

// memoize render function with some memoization library
import memoize from "memoize";

const renderItem =