No dynamic arrays in classes?

1

Not sure what I’m missing here, but if I create a new AS3 file with the following code:

function createArrays():void {
    for(var i:uint=0;i<3;i++){
        trace(i);
        this["array"+i]=new Array();
        this["array"+i].push("item1");
        this["array"+i].push("item2");
    }
    trace(this["array"+0].toString())
}
createArrays();

it traces fine and works…

If I set my document class to tst.as, remove all except the last line and put the following in a tst.as file:

package {

    import flash.display.MovieClip;
    import flash.events.*;

    public class tst extends MovieClip {
        
        public function createArrays():void {
            for(var i:uint=0;i<3;i++){
                trace(i);
                this["array"+i]=new Array();
                this["array"+i].push("item1");
                this["array"+i].push("item2");
            }
            trace(this["array"+0].toString())
        }
    }
}

I get an error saying:
ReferenceError: Error #1056: Cannot create property array0 on tst.
at tst/createArrays()
at tst/frame1()

Am I missing something, or are there functions you can’t build in external as but you can in the IDE?

Thanks!!