NextJS get markdown files in folder as data (properties) and content

getDocBySlug.js

export function getDocBySlug(dir, slug, fields = []) {
  const realSlug = slug.replace(/\.md$/, '');
  const fullPath = join('/base/', `${realSlug}.md`);
  const fileContents = fs.readFileSync(fullPath, 'utf8');
  const { data, content } = matter(fileContents);
  console.log(data, content);
  const items = {};

  // Ensure only the minimal needed data is exposed
  fields.forEach((field) => {
    if (field === 'slug') {
      items[field] = realSlug;
    }
    if (field === 'content') {
      items[field] = content;
    }

    if (data[field]) {
      items[field] = data[field];
    }
  }
  );

  return items;

}