code: function restifyCORSSimple(req, res, next) {
      var origin;
      if (!(origin = matchOrigin(req, origins))) {
        next();
        return;
      }
  
      function corsOnHeader() {
        origin = req.headers.origin;
  
        if (opts.credentials) {
          res.setHeader(AC_ALLOW_CREDS, 'true');
        }
  
        res.setHeader(AC_ALLOW_ORIGIN, origin);
        res.setHeader(AC_EXPOSE_HEADERS, headers.join(', '));
        res.setHeader(AC_ALLOW_METHODS, ALLOW_METHODS.join(', '));
        res.setHeader(AC_ALLOW_HEADERS, ALLOW_HEADERS.join(', '));
        res.setHeader(AC_REQUEST_HEADERS, REQUEST_HEADERS.join(', '));
      }
  
      res.once('header', corsOnHeader);
      next();
    }
docs: Handler for simple requests