如何在NodeJs中等待循环结束运行后再发回响应？

function asyncOperation(callback) {
  // 模拟一个异步操作
  setTimeout(callback, 1000);
}

app.get('/example', (req, res) => {
  const totalCount = 5; // 预期的异步操作次数
  let completedCount = 0; // 完成的异步操作次数

  for (let i = 0; i < totalCount; i++) {
    asyncOperation(() => {
      completedCount++;
      if (completedCount === totalCount) {
        // 所有异步操作完成后发送响应
        res.send('All operations completed.');
      }
    });
  }
});

function asyncOperation() {
  return new Promise(resolve => {
    // 模拟一个异步操作
    setTimeout(resolve, 1000);
  });
}

app.get('/example', async (req, res) => {
  const totalCount = 5; // 预期的异步操作次数
  const promises = [];

  for (let i = 0; i < totalCount; i++) {
    promises.push(asyncOperation());
  }

  await Promise.all(promises);
  res.send('All operations completed.');
});

function asyncOperation() {
  return new Promise(resolve => {
    // 模拟一个异步操作
    setTimeout(resolve, 1000);
  });
}

app.get('/example', async (req, res) => {
  const totalCount = 5; // 预期的异步操作次数

  for (let i = 0; i < totalCount; i++) {
    await asyncOperation();
  }

  res.send('All operations completed.');
});