Fix AsyncIterator Error in Svelte

What Is the AsyncIterator Error?

Seeing AsyncIterator pop up in your Svelte application? This guide covers the cause and a proven fix.

Why It Happens

This happens when async iteration protocols aren't properly implemented or when iterating over a non-async-iterable object.

The Fix

async function* fetchPages(url) {
  let page = 1;
  while (true) {
    const res = await fetch(`${url}?page=${page}`);
    const data = await res.json();
    if (data.length === 0) break;
    yield data;
    page++;
  }
}

for await (const page of fetchPages('/api/items')) {
  process(page);
}

Debugging Tips

When troubleshooting AsyncIterator in Svelte, start by checking your error logs for the full stack trace. The line number in the trace usually points directly to the problematic code. If the error only appears intermittently, it may be related to timing issues like race conditions or network latency. Adding structured logging around the failing operation can help narrow down the root cause. Make sure your local development environment mirrors production as closely as possible to reproduce the issue reliably.

Prevention

Tools like [Bugsly](https://bugsly.dev) catch these errors in production before users notice, providing full stack traces and context.

Key Takeaways

• Always handle this error gracefully with proper error handling
• Check your environment configuration
• Test thoroughly before deploying to production