Middleware dan Penangan Error Bertipe

import { RequestHandler } from 'express';
const authMiddleware: RequestHandler = (req, res, next) => {
  if (!req.headers.authorization) return res.status(401).json({});
  next();
};

import { Request, Response, NextFunction } from 'express';
function logger(req: Request, res: Response, next: NextFunction): void {
  console.log(req.method, req.path);
  next();
}

import { ErrorRequestHandler } from 'express';
const errorHandler: ErrorRequestHandler = (err, req, res, next) => {
  res.status(err.status ?? 500).json({ message: err.message });
};

class AppError extends Error {
  constructor(public message: string, public status: number = 500) {
    super(message);
  }
}

function asyncHandler(fn: RequestHandler): RequestHandler {
  return (req, res, next) => Promise.resolve(fn(req, res, next)).catch(next);
}

const authenticate: RequestHandler = async (req, res, next) => {
  const user = await verifyToken(req.headers.authorization);
  req.user = user; // requires module augmentation
  next();
};

function validate<T>(schema: ZodSchema<T>): RequestHandler {
  return (req, res, next) => {
    const result = schema.safeParse(req.body);
    if (!result.success) return res.status(400).json(result.error);
    req.body = result.data;
    next();
  };
}

router.use('/admin', authenticate, authorize('admin'));
router.get('/admin/users', asyncHandler(listUsers));

const requestLogger: RequestHandler = (req, _res, next) => {
  console.log(`${req.method} ${req.path}`);
  next();
};

app.use(requestLogger);
app.use('/api', apiRouter);
app.use(errorHandler); // must be last