After Effects uses JavaScript 1.2 for expressions, so if you’re pretty handy with ActionScript or JavaScript or the like, there’s a lot you can do within After Effects.
But what you cannot do with flash is to take an “Action-Scripted” animation and render it to use in broadcast or film – with After Effects you can.
One of the primary strengths of Flash is its ability to use scripting to calculate variables and attribute values on the fly, which keeps file sizes down and interactivity to a maximum. While its implementation may not be as strong or as easy as using Action Script in Flash 5, it has one critical advantage. One of the most powerful and yet often under utilised additions to After Effects from version 5 onwards is the inclusion of expressions.
