Async Svelte
15. Async Svelte, Streaming & Await Snippets
Build responsive async interfaces with Svelte 5 async components, streaming promise resolution in {#await} blocks, and non-blocking SSR hydration.
async-svelte.svelte
<script lang="ts">
// Svelte 5 Async Components & Streaming Promises
interface Telemetry {
nodeId: string;
rps: number;
latencyMs: number;
}
async function fetchTelemetry(): Promise<Telemetry> {
const res = await fetch('/api/telemetry');
return res.json();
}
let telemetryPromise = $state(fetchTelemetry());
</script>
<!-- Streaming Promise resolution without blocking UI hydration -->
{#await telemetryPromise}
<div class="animate-pulse p-6 bg-slate-100 dark:bg-slate-800 rounded-2xl">
<p class="text-base text-slate-500 font-mono">Connecting to edge stream...</p>
</div>
{:then data}
<div class="p-6 border border-emerald-500/40 rounded-2xl bg-emerald-50/20">
<h3 class="text-lg font-bold text-emerald-600">Edge Node: {data.nodeId}</h3>
<p class="text-base font-mono mt-1">Throughput: {data.rps} req/s | Latency: {data.latencyMs}ms</p>
</div>
{:catch error}
<div class="p-4 border border-rose-500/40 rounded-2xl text-rose-500 text-base">
Failed to load telemetry stream: {error.message}
</div>
{/await}Async Svelte, Streaming & Await Snippets
Svelte 5 enables non-blocking async component boundaries and streaming promises that decouple initial HTML shell hydration from slow backend responses.
- Streaming SSR with
{#await}: Allows the server to flush the page layout immediately while streaming deferred promise data down to the client as chunks complete. - Async Snippets: Pass asynchronous render snippets with parameters, avoiding layout shifts and manual loading state boilerplate.
- Resilient Catch Blocks: Isolate API errors locally to the component subtree without crashing or blanking the entire page view.
Async Component & Streaming Simulator Streaming SSR
Press "Fetch Async Stream" to test non-blocking promise resolution.