Trying to understand array references

In composition.ready:

var tileArray = new Array('ads', 'portfolio', logos', 'websites', 'oversize', directMail)

for (var i = 0; i<5; i++){

          grayscaleArray[i] = getSymbol(tileArray[i]).$(tileArray[i]+'TileGS');

}

In plain english this is what I want to do:

I want to click on a grayscale tile (for example grayscaleArray("adsTileGS") and then show the "adsPortfolio" symbol that is living in the library

So this is what I have done

for (var i = 0; i<grayscaleArray.length; i++){

                    grayscaleArray[i].click (function( ) {

     var arrayIndex =  HOW DO I GET THIS?  //need to get the array key value from the grayscaleArray for the tile that was clicked

     var arrayCategory = tileArray[arrayIndex]; //should return "ads"

     createChildSymbol (arrayCategory + "Portfolio", "Stage");  //should show "adsPortfolio" symbol on stage

     }