Should we use Promises?

[adalinesimonian]

Promises have the potential to significantly clear up a lot of async code that we have laying about. I think it's worth trying it out on a small scale and seeing whether or not it would be a good fit for the codebase we have.

[oren]

:+1:

We recently switched our containers to io.js and using promises whenever we have async operations. So far everyone on the team like it. it does add some boilerplate but I think it's worth it for the readability of the client that calling the promises.

I would suggest to try to use named functions whenever possible:

login().then(getUsers).then(saveAttachments).then(done).catch(error)

[adalinesimonian]

An example with some sample code similar to some stuff we have in Anvil Connect

Without Promises:

function someMiddleware(req, res, next) {

  Model.doSomeWork({ opt: 'val' }, function (err, model) {
    if (err) { return next(err); }
    if (!model) { return next(new Error('Invalid request')); }

    model.doSomethingElse(function (err, result) {
      if (err) { return next(err); }
      if (!result) { return next(new Error('Invalid options')); }

      if (result.x === 1) {

        model.doAnotherThing({ opt: result.y }, function (err, attr) {
          if (err) { return next(err); }

          if (attr) {
            res.render('view', { data: result.attrs[attr] });
          } else {
            res.render('view', { data: result });
          }
        });

      } else {
        res.render('view', { data: result });
      }
    });
  });

}

With Promises:

function someMiddleware(req, res, next) {

  Model.doSomeWork({ opt: 'val' }).then(function (model) {
    if (!model) { throw new Error('Invalid request'); }
    return model.doSomethingElse();

  }).then(function (result) {
    if (!result) { throw new Error('Invalid options'); }

    if (result.x === 1) {

      return model.doAnotherThing({ opt: result.y }).then(function (attr) {
        return attr ? result.attrs[attr] : result;
      });

    } else {
      return result;
    }

  }).then(function (data) {
    res.render('view', { data: data });
  }).catch(function (err) {
    next(err);
  });

}