svelte-infinite

Svelte Infinite

Svelte Infinite Loader designed and rebuilt specifically for use in Svelte 5 with runes

✨ Flexible
⏰ Infinite Loop Detection
📣 Control Loader State
🔎 IntersectionObserver based
🧑‍🔧 Demo: svelte-5-infinite.vercel.app

Svelte 5 is still early days, but I couldn't find an infinite loader-type component that was maintained for the last few years of Svelte 4. So I had recently built this for a Svelte 5-based application I was working on and was pretty happy with it, so I decided to clean it up and share it with the world! As Svelte 5 inevitably changes over the next weeks and months, I plan to keep this package updated and working with the latest available version of Svelte 5.

🏗️ Getting Started

1. Install svelte-infinite

npm install svelte-infinite
pnpm install svelte-infinite
yarn add svelte-infinite

1. Import both InfiniteLoader and loaderState from svelte-infinite

<script lang="ts">
  import { InfiniteLoader, loaderState } from "svelte-infinite"

  const allItems = $state([])

  const loadMore = async () => {
    const res = fetch("...")
    const data = await jes.json()
    allItems.push(...data)
    loaderState.loaded()
  }
</script>

<InfiniteLoader triggerLoad={loadMore}>
  {#each allItems as user (user.id)}
    <div>{user.name}</div>
  {/each}
</InfiniteLoader>

The component should wrap your list of items, and loaderState should be used in your triggerLoad function (and/or elsewhere) to interact with the internal state of the Loader component. You tell it whether you're out of data, ran into an error, etc.

See the example below and in this repository for more details.

🍍 Example

<script lang="ts">
  import { InfiniteLoader, loaderState } from "svelte-infinite"
  import UserCard from "$components/UserCard.svelte"

  const LOAD_LIMIT = 20
  const allItems = $state<{ id: number, body: string }[]>($page.data.items)
  let pageNumber = $state(1)

  // 1. You'll have to pass the InfiniteLoader component a load function
  // to its `triggerLoad` prop.
  const loadMore = async () => {
    // This is a relatively straight-forward load function with support for pagination
    try {
      pageNumber += 1
      const limit = String(LOAD_LIMIT)
      const skip = String(LOAD_LIMIT * (pageNumber - 1))

      // If there are less results on the first page (page.server loaded data)
      // than the limit, don't keep trying to fetch more. We're done.
      if (allItems.length < LOAD_LIMIT) {
        loaderState.complete()
        return
      }

      const searchParams = new URLSearchParams({ limit, skip })

      // Execute the API call to grab more data
      const dataResponse = await fetch(`/api/data?${searchParams}`)

      // Ideally, like most paginated endpoints, this should return the data
      // you've requested for your page, as well as the total amount of data
      // available to page through
      if (!dataResponse.ok) {
        loaderState.error()

        // On errors, set the pageNumber back so we can retry
        // that page's data on the next 'loadMore' attempt
        pageNumber -= 1
        return
      }
      const data = await dataResponse.json()

      // If we've received data, push it to the reactive state variable
      // rendering our items inside the `<InfiniteLoader />` below.
      if (data.items.length) {
        allItems.push(...data.items)
      }

      // If there are more (or equal) number of items loaded as are totally available
      // from the API, don't keep trying to fetch more. We're done.
      if (allItems.length >= data.totalCount) {
        loaderState.complete()
      } else {
        loaderState.loaded()
      }
    } catch (error) {
      console.error(error)
      loaderState.error()
      pageNumber -= 1
    }
  }
</script>

<main class="container">

    <!-- 2. Here you wrap your items with the InfiniteLoader component -->

    <InfiniteLoader triggerLoad={loadMore}>
      {#each allItems as user (user.id)}
        <UserCard {user} />
      {/each}

      <!-- 3. There are a few optional snippets for customizing what is shown at the bottom
           of the scroller in various states, see the 'Snippets' section for more details -->
      {#snippet loading()}
        Loading...
      {/snippet}
      {#snippet error(load)}
        <div>Error fetching data</div>
        <button onclick={load}>Retry</button>
      {/snippet}
    </InfiniteLoader>
</main>

</script>

♾️ Usage

This package consists of two parts, first the InfiniteLoader component which is a wrapper around your items. It will trigger whichever async function you've passed to the triggerLoad prop when the user scrolls to the bottom of the list.

Second, there is also a loaderState import which you should use to interact with the internal state of the loader. For example, if your fetch call errored, or you've reached the maximum number of items, etc. you can communicate that to the loader. The most basic usage example can be seen in the 'Getting Started' section above. A more complex example can be seen in the 'Example' section, and of course the application in /src/routes/+page.svelte in this repository also has a "real-world" usage example.

loaderState

The loaderState import is an object with 4 methods on it:

• loaderState.loaded()
  • Designed to be called after a successful fetch.
• loaderState.error()
  • Designed to be called after a failed fetch or any other error. This will cause the InfiniteLoader to render a "Retry" button by default, or the error snippet.
• loaderState.complete()
  • Designed to be called when you've reached the end of your list and there are no more items to fetch. This will render a "No more data" string, or the no-data snippet.
• loaderState.reset()
  • Designed to be called when you want to reset the state of the InfiniteLoader to its initial state, for example if there is a search input tied to your infinite list and the user enters a new query.

Props

• triggerLoad: () => Promise<void> - required
  • The async function to call when we should attempt to load more data to show.
• intersectionOptions: IntersectionObserverInit = { rootMargin: "0px 0px 200px 0px" } - optional
  • The options to pass to the IntersectionObserver instance. See MDN for more details. The default rootMargin value will cause the target to intersect 200px earlier and trigger the loadMore function before it actually intersects with the root element (window by default). This has the effect of beginning to load the next page of data before the user has actually reached the current bottom of the list, making the experience feel more smooth.
  • It may also be required to pass in a reference to your scroll container as the root option, if your scroll container is not the window.
• loopTimeout: number = 2000 - optional
  • If the loopMaxCalls is reached within the detection timeout, a cool down period is triggered of this length (in milliseconds).
• loopDetectionTimeout: number = 1000 - optional
  • The time in milliseconds in which the loopMaxCalls count must be hit in order to trigger a cool down period of loopTimeout length.
• loopMaxCalls: number = 5 - optional
  • The number of calls to the triggerLoad function within timeout which should trigger cool down period.

Snippets

Snippets replace slots in Svelte 5, and as such are used here to customize the content shown at the bottom of the scroller in various states. The InfiniteLoader component has 4 props for snippets available.

• loading
  • Shown while calling triggerLoad and waiting on a response.
• noResults
  • Shown when there are no more results to display and we haven't fetched any data yet (i.e. data is less than count of items to be shown on first "page").
• noData
  • Shown when loaderState.complete() is called, indicating we've fetched and displayed all available data.
• coolingOff
  • Shown when loaderState !== "COMPLETE" and a loop has been detected. Will disappear and loopTimeout when the cooling off period expires.
• error
  • Shown when there is an error or loaderState.error() has been called. The snippet has an attemptLoad parameter passed to it which is just the internal triggerLoad function, designed for a "Retry" button or similar.

📦 Contributing

• Initially inspired by jonasgeiler/svelte-infinite-loading
• Open to contributions, issues, and feedback 🙏

📝 License

MIT