REST API with Express

// Helper functions
const successResponse = (res, data, statusCode = 200) => {
  res.status(statusCode).json({ success: true, data });
};

const errorResponse = (res, message, statusCode = 400) => {
  res.status(statusCode).json({ success: false, error: message });
};

// Validation middleware
function validateUser(req, res, next) {
  const { name, email } = req.body;
  const errors = [];
  
  if (!name || name.trim().length < 2) {
    errors.push("Name must be at least 2 characters");
  }
  
  if (!email || !/^[^s@]+@[^s@]+.[^s@]+$/.test(email)) {
    errors.push("Valid email required");
  }
  
  if (errors.length > 0) {
    return res.status(422).json({ 
      success: false, 
      errors,
      message: "Validation failed" 
    });
  }
  
  next(); // validation passed
}

// Routes with validation
app.post("/api/users", validateUser, (req, res) => {
  const user = createUser(req.body);
  successResponse(res, user, 201);
});

// Global error handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ 
    success: false, 
    error: "Internal Server Error" 
  });
});

// 404 handler
app.use((req, res) => {
  errorResponse(res, `Route ${req.method} ${req.path} not found`, 404);
});