An example of using Blend.

blend.js

 app.use(function(req, res, next) {
  res.blend = function(params) {
    params.buildData(params.params, function(e, d) {
      if(req.headers['content-type'] === 'application-json') {
          res.json(d);
      } else {  // render html
        params.buildSelectors(d, function(selectors) {
          var options = {
            layout: (req.param('_pjax')) ? null : params.layout,
            container: params.container || '#container',
            selectors: selectors
          };
          if(req.headers['content-type'] === 'blend') {
              res.json({
                template: params.template,
                selectors: options
              });

          }else {
            res.render(params.template, options);
          }
        });
      }
    });
  };
  next();
 });

ExampleUsage.js

 /*

Blend middleware for Express.js 

Exposes not only the data but also the object which would get passed to the templating language so that we can do the rendering in the browser.

An example usage:

*/
res.blend({
    buildData: function(params, callback) {
      // return all data required to load the page in the callback.
      db.getData(params.id, callback;
    },
    buildSelectors: function(data, callback) {
      // convert data into object to be passed to templating engine.
      var selectors = {};
      selectors['.username'] = req.session.username;
      selectors['#widgets'] = {
        partial: 'target',
        data: sizlate.classifyKeys(data, {classifyKeys: true })
      };
    return callback(selectors);
  },
  template: 'targets',
  layout: 'layout'
});