` _{for Preact}

A "virtual" list component that renders only visible rows of a given data set.

Useful for those super important business applications where one must show all million rows.

Demo

Usage Example

Provide the list of items as data, an item renderer as renderRow, and the height of a single row as rowHeight. Everything else is optional.

<VirtualList
    data={['a', 'b', 'c']}
    renderRow={ row => <div>{row}</div> }
    rowHeight={22}
    overscanCount={10}
    sync
/>

Props

Prop	Type	Description
`data`	Array	List of data items
`renderRow`	Function	Renders a single row
`rowHeight`	Number	Static height of a row
`sync`	Boolean	If `true`, forces synchronous rendering *
`overscanCount`	Number	Number of extra rows to render above and below visible list. Defaults to 10. **

* About synchronous rendering: It's best to try without sync enabled first. If the normal async rendering behavior is fine, it's best to leave sync turned off. If you're seeing flickering, enabling sync will ensure every update gets out to the screen without dropping renders, but does so at the expense of actual framerate.

** Why overscan? Rendering normalized blocks of rows reduces the number of DOM interactions by grouping all row renders into a single atomic update.

Without Overscan	With Overscan

Simple Example

View this example on JSFiddle

import VirtualList from 'preact-virtual-list';

// Generate 100,000 rows of data
const DATA = [];
for (let x=1e5; x--; ) DATA[x] = `Item #${x+1}`;

class Demo extends Component {
    // 30px tall rows
    rowHeight = 30;

    // Renders a single row
    renderRow(row) {
        return <div class="row">{row}</div>;
    }

    render() {
        return (
            <VirtualList sync class="list"
                data={DATA}
                rowHeight={this.rowHeight}
                renderRow={this.renderRow}
            />
        );
    }
}

render(Demo, document.body);

Functional Example