function findGroups(layerName) {
  var numberOfLayers = app.activeDocument.layers.length; // numberOfLayers was not defined
    for (var i = 0; i < numberOfLayers; i++) {
        var currentLayer = app.activeDocument.layers[i].name;
        if (currentLayer == layerName) {
            var numberOfSublayers = app.activeDocument.layers[i].layers.length; // Number of sublayers
            for (var x = 0; x < numberOfSublayers; x++) { // Dont use the i variable twice in the same function. It could work but not best practice.
                alert(app.activeDocument.layers[i].layers[x]) // Alert the sublayers
            }  
        }
    }
}
 
 
findGroups("My Layer"); // Case Sensitive
 

Oh where have they put the advanced editor? No code thing… Oh well never mind… This should suffice… getByName() should go in atry catch but you get the idea…

#target illustrator
 
var doc = app.activeDocument;
 
var grps = doc.layers.getByName( 'my layer' ).groupItems;
 
for ( var i = 0; i < grps.length; i++ ) {
 
          doc.selection = null;
 
          grps[i].selected = true;
 
          app.redraw();
 
          alert( 'group '+ ( i+1 ) );
 
};

See pic for difference between types…

Am I having a bit of a thick moment or do I really have to post then go back and edit to get the advanced features…?

I see Jive is going the route of CS… take something useful away then call it an improvement when you put it back… Keep that in mind for your scripts…

That is NOT what I get… Collections have scope to their parent container… When my snippet was run against the pictured doc it selected only the 4 groups in my Layer all other top layers had groups in them…

app.redraw(); is just a script method that should cause the GUI window to update by default this does NOT happen for performace… So using it slows things down… I have had some occasions where it has not worked but a dialog will force that… It shouldn't fix anything but I wanted the highlighted selecion to be visible…