传递来自express服务的错误消息

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

app.get('/api/users/:id', (req, res, next) => {
  const userId = req.params.id;

  // 模拟数据库查询错误
  if (userId !== '123') {
    const error = new Error('User not found');
    error.status = 404;
    return next(error);
  }

  // 正常情况下返回用户信息
  const user = { id: userId, name: 'John Doe' };
  res.json(user);
});

// 错误处理中间件
app.use((err, req, res, next) => {
  const status = err.status || 500;
  const message = err.message || 'Internal Server Error';
  
  // 发送错误消息给客户端
  res.status(status).json({ error: message });
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});