Illustrator Scripting :: Selecting Text Frames On All Visible Layers

I want to select all text frames on all visible layers. The script below will select all text frames even in groups but when a layer with text on it is invisible the script will error.(target layer cannot be modified)
 
if (app.documents.length > 0 ) {
var doc = app.activeDocument;
var numTextFrames = 0;
for (  i = 0; i < doc.textFrames.length; i++ ) {
textArtRange = doc.textFrames[i];
textArtRange.selected = true;
}
}
 
So I made this script to select text frames on only the visible layers but it now misses text that is in a group.
 
var layerCount = activeDocument.layers.length;
var docSelected = activeDocument.selection;
for (i = 0; i < layerCount; i++)

[Code] .....

Why it does not selected textframes in a group when done this way and is there a way to get all textframes selected on all visible layers?