code: function servePage(bundle, opts) {
    opts = opts || {};
  
    if (typeof bundle !== 'function') {
      bundle = bundler.create(bundle, opts);
    }
  
    return function(req, res, next) {
      var location = makeLocation(req, opts.origin);
      var clientReq = request.createRequestFromLocation(location);
      bundle()
        .then(function(bundle) {
          return evaluatePromise({
            bundle: bundle,
            code: renderComponentToString(clientReq),
            debug: opts.debug,
            location: location
          });
        })
        .then(function(rendered) {
          var init = renderComponent(rendered.request.data);
          var markup = rendered.markup.replace(
            '</head>',
            '<script>' + init + '</script>'
          );
          res.setHeader('Content-type', 'text/html');
          res.statusCode = rendered.isNotFoundErrorHandled ? 404 : 200;
          res.write(markup);
          res.end();
        }, function(err) {
          err.isNotFoundError ? res.send(404) : next(err);
        });
    }
  }
docs: Middleware for serving pre-rendered React UI
  
  @param {Bundler|Browserify|ModuleId} bundle
  @param {Options} opts