load-options.js

const thisYear = new Date().getFullYear();

module.exports = (req, res, next) => {
  const parts = req.url.split('/');

  res.locals.options = parts.reduce(
    (acc, curr) => {
      if (!curr) return acc;

      let match = curr.match(/^@?(\d{4})$/) || [];

      if (match.length) {
        // Pinned year
        if (curr.startsWith('@')) {
          acc.pinnedYear = parseInt(curr.substr(1), 10);
        } else {
          acc.startYear = parseInt(curr, 10);
        }
        return acc;
      }

      match = curr.match(/^(\d{4})-(\d{4})$/) || [];

      if (match.length) {
        acc.startYear = parseInt(match[1], 10);
        acc.endYear = parseInt(match[2], 10);

        return acc;
      }

      if (curr.startsWith('license')) {
        acc.format = curr
          .split('.')
          .pop()
          .trim();
        return acc;
      }

      if (curr.startsWith('+')) {
        acc.license = curr.substr(1).toUpperCase();
        return acc;
      }

      acc.sha = curr; // not actually supported now - 2019-06-19
      return acc;
    },
    {
      format: 'html',
      startYear: null,
      endYear: thisYear,
      sha: null,
    }
  );

  if (res.locals.options.sha) {
    res.setHeader(
      'X-note',
      'SHA and commit pinning is no longer supported, showing you latest release'
    );
  }

  next();
};