nextjs-handler-allow-methods-middleware.ts

import { use, Middleware } from 'next-api-route-middleware';

export const allowMethods = (allowedMethods: string[]): Middleware => {
  return async function (req, res, next) {
    if (allowedMethods.includes(req.method!) || req.method == 'OPTIONS') {
      next();
    } else {
      res.status(405).send({ message: 'Method not allowed.' });
    }
  };
};

export default use(allowMethods['GET'], handler);

thank you! btw where to rewrite next()?

next is made available as a parameter to the middleware function, along with req and res. You call it when your middleware has finished and it will invoke the next middleware function, or the handler if there are no more middleware functions.