templater.js

// render .js files as templates (they must be function taking options as arguments and outputting a valid HTML string)
app.engine('js', function (filePath, options, callback) {
  if (process.env.NODE_ENV !== 'production') {
    require.cache[filePath] = undefined; // invalidate require cache in dev
  }
  callback(null, require(filePath)(options)); // note: should wrap in a safeHtml in prod
});
app.set('views', __dirname + '/views');
app.set('view engine', 'js');

// VS
app.engine('js', reactEngine);

function reactEngine(filePath, options, callback) {
  const component = require(filePath);
  const markup = renderToStaticMarkup(createElement(component, options));
  callback(null, markup);
}