pfadi-bussle/pages/api/booked.js

// Next.js API route support: https://nextjs.org/docs/api-routes/introduction

export default (req, res) => {
  res.statusCode = 200
  res.json({
    bookedOn: [
      '2020-07-10',
      '2020-07-11',
      '2020-07-12',
      '2020-07-23',
      '2020-08-01',
    ],
  })
}