Express for Harmony

How it works

Require this package instead of express to be able to use Harmony generators as middleware and callbacks. They will automatically be wrapped with code that handles promises in the background, allowing your handlers to look like this:

router.get('/:id', function* (req, res) {
  var obj = yield req.db.findOne({ _id: req.params.id });

  if (obj) {
    res.json(obj)
  } else {
    res.status(404).json({ err: "Not found" });
  }
});

The same goes for error handlers and middleware.

Errors

Errors coming from generator handlers or middleware will be funneled properly to error handlers. This is true to ones raised by sync code and ones coming from promises as well.

You can install a generic error handler to catch all exceptions that were not caught in your route handlers.

The following (admittedly pointless) example demonstrates the idea:

var read = Q.denodeify(fs.readFile);

// Omitting some boilerplate with router and app.

router.get('/read/:fname', function* (req, res) {
  var file = yield read(req.params.fname);
  res.json({ content: file });
});

app.use(function (err, req, res, next) {
  res.status(500).json({ code: err.code });
})

Calling the above route with a non-existent filename will cause a status of 500 to be returned along with the content {"code":"ENOENT"}.

steerio/express-harmony

Express for Harmony

How it works

Errors