Improve bkEventExecutor interface implementation

What was done before isn't valid JS; This does the same thing, while keeping the JS syntax valid.

In short, while I was working on my JSC, my buildscripts couldn't minify events.js because the syntax was invalid. After some googling, I decided to try doing what I have proposed in the pull request, and so far from what I'm looking at, it works exactly the same, while keeping the JS syntax valid.