Closures in Actionscript 3.0
For right now, this is a direct copy of a forum post (with a hard character limit on posts). I might come back and spiff it up some, but then again maybe not. I DO WHAT I WANT!
It’s on closures, and it’s stuff you need to know before looking at the stuff on partial application. You don’t necessarily need to know the stuff I address here specifically, just what a closure is and stuff.
First, before I even start to get into this, I want to say that Actionscript is an ECMAScript derivative. Javascript also falls into this category, so you can often find tutorials, examples, etc which translate easily from one language to another. A VERY good explanation of Closures and a few of their uses can be found here, but is biased towards Javascript, and isn’t the most accessible thing out there 
Second, the uses of a “closure” are not really a clear-cut. If someone asked you “what can a class be used for?”, there would be no single definite way to answer the question. Closures, in fact, can almost be thought of as another way of representing a class (but don’t think of them that way!), but offer other practical uses as well. In this example, we’ll discuss what a closure is and then use one to help solve the common problem of “passing arguments to event handlers”, as well as pick up a nifty trick or two.