Select ungrouped items, change opacity and save

Question

Hi, I am a javascript beginner trying to create a script to do the following to several . ai files, one at a time:
open document
select all items
change opacity to 40%
select all grouped items
change opacity to 100%
save and close
This is what I have so far which I know only affects the opacity of one layer, but if anybody has any tips for what I can do next, it would be greatly appreciated.
for ( i = 0; i < app.documents.length; i++ ) {
    var targetDocument = app.documents[i];
    var layerCount = targetDocument.layers.length;
        for (var ii = layerCount - 1; ii >= 0; ii-- ) {
            targetLayer = targetDocument.layers[ii];
            var layerName = new String( targetLayer.name );
                if ( layerName.indexOf("TEST") == 0 ) {
                    targetDocument.layers[ii].opacity=40.0;
targetDocument.close;
targetDocument = null;

Answer 1

You don't select in script but does this do what you meant?
#target illustrator
setObjectOpacity()
function setObjectOpacity() {
    var doc = app.activeDocument;
    for ( var i = 0; i < doc.pageItems.length; i++ ) {
        doc.pageItems[i].opacity = 40; // This will do everything
    for ( var i = 0; i < doc.groupItems.length; i++ ) {
        doc.groupItems[i].opacity = 100; // Put this back
        for ( var j = 0; j < doc.groupItems[i].pageItems.length; j++ ) {
            doc.groupItems[i].pageItems[j].opacity = 100; // Put these back too