Array lenght

Hi folks!

I start with an array of gameobject, filled via editor.

Then I want to manage this array, or better, a copy of it to remove elements, I need to know what's the size of the new array by I alway get null :(...

Here is my code:

 var sourceTiles : GameObject[];

function Start () {

 var tiles = new Array (sourceTiles);
 
 print(tiles.Lenght);//i get null :(
 
 
 
 //this is a simplyfication of the loop that I need to remove
 
 for (var i : int = 0; i < tiles.Lenght; i++)
     tiles.RemoveAt(i);

}

Maybe I need to understand better how to use builtin array and jsarray...:(

really thanks :)