res.render Override Middleware

res.render.js

/**
 * Override res.render to do any pre/post processing
 */
app.use(function(req, res, next) {
  var render = res.render;
  res.render = function(view, options, fn) {
    var self = this,
      options = options || {},
      req = this.req,
      app = req.app,
      defaultFn;

    if ('function' == typeof options) {
      fn = options, options = {};
    }

    defaultFn = function(err, str){
      if (err) return req.next(err);
      self.send(str);
    };

    if ('function' != typeof fn) {
      fn = defaultFn;
    }

    render.call(self, view, options, function(err, str) {
      // do whatever post processing you want
      fn(err, str);
    });
  };
  next();
});