编写关键nodejs后端函数的最佳方式是什么？

// example.js
const exampleFunction = (req, res) => {
  // 处理请求
};

module.exports = { exampleFunction };

const exampleFunction = async (req, res) => {
  try {
    const result = await someAsyncOperation();
    res.status(200).send(result);
  } catch (error) {
    res.status(500).send(error.message);
  }
};

const exampleFunction = async (req, res) => {
  try {
    const result = await someAsyncOperation();
    res.status(200).send(result);
  } catch (error) {
    console.error(error);
    res.status(500).send('Internal Server Error');
  }
};

const express = require('express');
const app = express();

app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  next();
});

app.get('/example', exampleFunction);

/**
 * 处理示例请求
 * @param {Object} req - 请求对象
 * @param {Object} res - 响应对象
 */
const exampleFunction = async (req, res) => {
  // ...
};

const { exampleFunction } = require('./example');

test('exampleFunction should return correct result', async () => {
  const req = {};
  const res = { status: jest.fn().mockReturnThis(), send: jest.fn() };
  await exampleFunction(req, res);
  expect(res.status).toHaveBeenCalledWith(200);
  expect(res.send).toHaveBeenCalledWith('expected result');
});

const dbConnectionString = process.env.DB_CONNECTION_STRING;