text: import posts from './_posts';
  
  const lookup = new Map();
  posts.forEach((post) => {
    lookup.set(post.slug, JSON.stringify(post));
  });
  
  export function get(req, res) {
    // the `slug` parameter is available because
    // this file is called [slug].json.js
    const { slug } = req.params;
  
    if (lookup.has(slug)) {
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(lookup.get(slug));
    } else {
      res.writeHead(404, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({ message: 'Not found' }));
    }
  }
  