In describing the ConcurrencyMaster, I referred to Bluebird promisify as a magic function. Of course, it’s not really magical, it’s just a computer program. It only seemed magical because I didn’t understand how it worked. So this week, I’ve taken the opportunity to fill this hole in my knowledge by studying the internal workings of promisify. I like to learn about projects by fixing bugs in them, but Bluebird has no open bugs. Instead, we’ll just run through the working code and see what makes the magic happen. Here goes!