How to acces an array inside an array ?

I could acces it but is there a fastet/better way to do it ? (In js)

var a = new Array();

a = GameMaster.Couldbehit[0];
var b:boolean = a[4];
Debug.Log(b);

So i have an array that contains some other arrays.

and i want to acces one member of the array inside the array.

Something like this but it don’t works : GameMaster.Couldbeit[0].Couldbehitar[4]

It is !! Here’s the code that make the array inside an array:

static var Couldbehit = new Array();
static var Couldbehitar = new Array();

Couldbehitar.Add(false);
Couldbehitar.Add(false);
Couldbehitar.Add(false);
Couldbehitar.Add(false);
Couldbehitar.Add(true);
Couldbehit.Add(Couldbehitar); 

as multiple object add their own array inside the array i could not use simply GameMaster.Couldbehitar but i need something like GameMaster.Couldbehit[y].Couldbehitar