Thanks for the tip. I did not know this and unfortunately I didn't see it anywhere in the documentation.
https://github.com/steemit/steem-js/tree/master/doc

However now you mention it I do see it as a dependency in the node_modules directory.
I'm going to keep using promisify because it's working (so far), and I have all the code already written and don't want to have to refactor it. I'll keep it in mind for future projects though.

Thank you so much!