2d arrays inside constructor function

programming flash
1

I have a problem that i think i can solve if i create a 2d array based on another two arrays
Im trying something like that


var my2dAr:Array = new Array();
var i = ar1.length;
var j = ar2.length;
while(i--){
my2dAr* = new Array();
while(j--){
my2dAr*[j] = false;
}
}

inside the constructor function of myclass but it seems that it makes the script too slow and unresponsible
So is there any way to make this 2d array inside this constructor function?OR a way to fake it?
Thanks