对循环中的异步块感到困惑

async function processItems(items) {
  for (const item of items) {
    await asyncOperation(item);
  }
}

async function processItems(items) {
  const results = await Promise.all(items.map(async (item) => await asyncOperation(item)));
  return results;
}

async function asyncOperation(item) {
  const timeout = 5000; // 5秒超时
  const controller = new AbortController();
  const timeoutId = setTimeout(() => controller.abort(), timeout);

  try {
    const response = await fetch(item.url, { signal: controller.signal });
    clearTimeout(timeoutId);
    return response.json();
  } catch (error) {
    if (error.name === 'AbortError') {
      console.error('Operation timed out');
    } else {
      console.error('Operation failed', error);
    }
  }
}