AbortController-Wrapped Fetch

export async function fetchAbortable(
  url: string,
  opts: RequestInit & { timeoutMs?: number } = {},
): Promise<Response> {
  const { timeoutMs, signal: externalSignal, ...rest } = opts;
  const ctl = new AbortController();
  const onAbort = () => ctl.abort(externalSignal?.reason);
  externalSignal?.addEventListener('abort', onAbort, { once: true });

  const timeoutId = timeoutMs
    ? setTimeout(() => ctl.abort(new Error(`Timed out after ${timeoutMs}ms`)), timeoutMs)
    : undefined;

  try {
    return await fetch(url, { ...rest, signal: ctl.signal });
  } finally {
    if (timeoutId) clearTimeout(timeoutId);
    externalSignal?.removeEventListener('abort', onAbort);
  }
}

const ctl = new AbortController();
const resp = await fetchAbortable('/api/slow', { signal: ctl.signal, timeoutMs: 5000 });