1.js

function preventUnhandledRejections(...promises) {
  for (const promise of promises) promise.catch(() => {});
}

async function showChapters(chapterURLs, { signal: outerSignal }) {
  outerSignal?.throwIfAborted();
  const controller = new AbortController();
  outerSignal?.addEventListener('abort', () => controller.abort());

  const chapterPromises = chapterURLs.map(async (url) => {
    const response = await fetch(url, { signal: controller.signal });
    let data;
    
    try {
      data = await response.json();
    } catch (err) {
      throw Error(`Failed to parse ${url} as JSON: ${response.statusCode} ${response.statusText}`);
    }
    
    if (data.error) throw Error(data.error);
    return data;
  });

  // Avoid unhandled rejections leaking out of this function.
  // The subsequent `for await` handles all the relevant promises.
  preventUnhandledRejections(...chapterPromises);

  try {
    for await (const chapterData of chapterPromises) {
      appendChapter(chapterData);
    }
  } finally {
    // Abort any remaining fetches
    controller.abort();
  }
}