semaphore/routes/_components/Timeline.html

<div class="timeline">
  <VirtualList component="{{StatusListItem}}"
               items="{{statuses}}"
               on:scrollToBottom="addMoreItems()" />
</div>
<style>
  .timeline {
    min-height: 50vh;
  }
</style>
<script>
  import { store } from '../_utils/store'
  import { getHomeTimeline } from '../_utils/mastodon/oauth'
  import fixture from '../_utils/fixture.json'
  import StatusListItem from './StatusListItem.html'
  import VirtualList from './VirtualList.html'
  import { splice, push } from 'svelte-extras'

  let i = -1

  const createData = () => fixture.slice(0, 20).map(_ => ({
    key: `${++i}`,
    props: _
  }))

  export default {
    data: () => ({
      target: 'home',
      statuses: createData(),
      StatusListItem: StatusListItem
    }),
    store: () => store,
    components: {
      VirtualList
    },
    methods: {
      splice: splice,
      push: push,
      addMoreItems() {
        console.log('addMoreItems')
        let statuses = this.get('statuses')
        if (statuses) {
          let itemsToAdd = createData()
          if (itemsToAdd.length) {

          }

          let importantFirstItem = itemsToAdd
          this.splice('statuses', statuses.length, 0, ...itemsToAdd)
        }
      },
      addTheseItems(items) {
        if (!items.length) {
          return
        }
        this.push(items.pop())
        while (items.length) {
          this.addItemLazily(items.pop())
        }
      },
      addItemLazily(item) {
        requestIdleCallback(() => {
          this.push(item)
        })
      }
    }
  }
</script>