Node-Coroutine-Brilliance.js

import Bluebird from 'bluebird';
// assume express, promise-ready ORM (Sequelize, Bookshelf, Mongoose)

function wrap(genFn) {
    var cr = Bluebird.coroutine(genFn);
    return function (req, res, next) {
      cr(req, res, next).catch(next);
    }
}

app.get('/', wrap(function*(req, res) {
  if (!isRequestValid(req)) {
    // throws will be sent to the err handler
    // Many error types can be made for all the status codes to simplify code
    throw new BadRequestError('The request was invalid!');
  }

  // if there's an error with yield fail, it'll be passed to the err handler
  var items = yield Items.find({}).exec();

  // if you have extra stuff to fetch that are determined by flags
  // and the extra stuff can be fetched in parallel.
  var extraFetchers = [];

  if (needStuff1) {
    extraFetchers.push(Stuff1.find({}).exec());
  } else {
    // this makes sure that the index of stuff1 and stuff2 is always the same
    extraFetchers.push(Promise.resolve(null));
  }
  if (needStuff2) {
    extraFetchers.push(Stuff2.find({}).exec());
  } else {
    extraFetchers.push(Promise.resolve(null));
  }

  // if we have array destructuring, it's super handy
  var [stuff1, stuff2] = yield extraFetchers;
  // if not, var stuffs = yield extraFetchers;

  res.locals.items = items;
  res.locals.stuff1 = stuff1; // could do stuffs[0] if we didn't have array destructuring
  res.locals.stuff2 = stuff2; // and stuffs[1]
  res.render('mypage');
});

app.use(function(err, req, res, next) {
  // handle error
  res.locals.err = err;
  res.render('errpage');
});