code: function serverRender(req, res, next) {
    var app = req.app;
  
    var { themes, defaultTheme } = app.locals;
    var { zlSite } = res.locals;
  
    if (!zlSite || !themes[zlSite.zsTheme]) return next();
  
    // determine if to use servBundle
    if ('production' === app.get('env') && themes[zlSite.zsTheme].servBundle) {
      themes[zlSite.zsTheme].servBundle(req, res);
    }
    else {
      // not using servBundle, transpile in real-time
      require("babel-register");
  
      // find the 1st serverRenderFile in themeTree
      let rendered = false;
      _.forEach(zlSite.themeTree, function(v, key) {
        if (themes[key].zealderConfig && themes[key].zealderConfig.serverRenderFile) {
          var serverRender = require(`${themes[key].path}/${themes[key].zealderConfig.serverRenderFile}`);
          serverRender(req, res);
          rendered = true;
          return false;
        }
      });
      if (!rendered) {
        // if none of the themes in tree provided serverRenderFile, use default
        var serverRender = require(`${themes[defaultTheme].path}/${themes[defaultTheme].zealderConfig.serverRenderFile}`);
        serverRender(req, res);
      }
    }
  }
docs: loads pages