AFX Script Problem Visual Studio Code

Hi, 

i recently started scripting and wrote a script in VS Studio for After Effects, which works fine when i run it from Visual Studio. But when i save it and run the script from After Effect it gives me an error message: "unable to execute at line 20..."  

which is a function in my script. everything before gets executed. 

I have Variables (a,b)  in my function because i am looking for several Objects meaning CompItem, FootageItem, Folderitem where I'm looking for specific names as a string. 

The Function looks like that: 

function graballItems(a, b) {
  var proj, curItem, itemTotal, ItemAry;

  proj = app.project;

  itemTotal = proj.numItems;

  ItemAry = new Array();

  for (var i = 1; i <= itemTotal; i++) {
    curItem = proj.item(i);

    if (curItem instanceof b && curItem.name.indexOf(a) !== -1) {
      ItemAry = curItem;
    }
  }
  return ItemAry;
}

// And i use it like that:

var myCompBeauty = graballItems("CAN_ENDTAG_PRE", CompItem);

But strange though, that it is working from VS Studio. 

Does anybody know why the error message appears? 

Cheers 

Martin