c2n/web-componentsv0.0.16
ComponentsIconsGuidesExamplesGetting started
ComponentsIconsGuidesExamplesGetting started
GitHub repository

Virtual List

Windowed list with built-in search, sorting, selection and an async data source.

c2-virtual-list renders only the rows you can see. It windows items to the visible range plus an overscan margin with the same virtual scroller the data grid uses, so 50 000 rows cost the same DOM as twenty — and every visible row is a real c2-list-item, so the markup, slots, selection styling and theme are the ones you already know from c2-list.

Search is part of the component rather than something you bolt on: searchable puts a field above the list, search is also a plain property so an external input can drive it, search-fields narrows what a query is matched against, matcher replaces the matching outright, and highlight marks what matched. sort orders the rows. An async dataSource swaps the whole thing for block loading, with the query and the sort delegated to the server.

Give the host a height (or --c2-virtual-list--max-height); the rows scroll inside it. Windowing needs a uniform row height, which comes from --c2-virtual-list__item--height — a list with two-line rows has to raise it. Tab moves into the list, the arrow keys, Home, End, PageUp and PageDown walk the rows, Enter or Space selects, ⌘/Ctrl-click toggles and shift-click selects a range.

Installation

npm install @c2n/virtual-list

@c2n/list-item, @c2n/text-field and @c2n/spinner are dependencies of the package and are registered for you.

Usage

Hand the list its items — an array in the property, JSON in the attribute — and say which field is the label. Without label-field the list falls back to label, name, title or value, so a list of plain objects (or of bare strings) needs no configuration at all.

Searching a million rows

With a dataSource the list holds nothing: it asks for one block at a time as rows scroll into view, and hands the query and the sort to the server. Rows whose block has not arrived render as skeletons, so the list never jumps.

const list = document.querySelector('c2-virtual-list')

list.dataSource = {
  async getItems({ start, count, search, sort }) {
    const response = await fetch(`/api/people?start=${start}&count=${count}&q=${search}&sort=${sort?.field ?? ''}`)
    const page = await response.json()
    return { items: page.rows, total: page.total }
  },
}

Custom rows

renderItem replaces the label/description pair with any markup — the row is still a c2-list-item, so its slots are yours.

import { html } from 'lit'

list.renderItem = ({ item }) => html`
  <c2-feather-user slot="prefix-icon"></c2-feather-user>
  <strong>${item.name}</strong>
  <span slot="description">${item.team} · ${item.score.toLocaleString()}</span>
`
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