How to duplicate a document?

Question

Hi guys,
I need to run a script that performs some modifications to the file, and in order to do that I would like to be working on a temp file.
process:
- run the script
- script duplicates file
- script runs on duplicated file
- close/dump duplicate file
I need help with the duplication process, i've done it before in a PSD script but the API seems to be different for Illustrator.
here's an AI example taken from "AI CS4 scripting reference"
// Duplicates any selected items from
// the active document into a new document.
var newItem;
var docSelected = app.activeDocument.selection;
if ( docSelected.length > 0 ) {
     // Create a new document and move the selected items to it.
     var newDoc = app.documents.add();
     if ( docSelected.length > 0 ) {
          for ( i = 0; i < docSelected.length; i++ ) {
               docSelected[i].selected = false;
               newItem = docSelected[i].duplicate( newDoc, ElementPlacement.PLACEATEND );
     else {
          docSelected.selected = false;
          newItem = docSelected.parent.duplicate( newDoc,ElementPlacement.PLACEATEND );
else {
     alert( "Please select one or more art objects" );
Now although this can be tweaked to duplicate all layers, wether selected or not, it doesn't maintain the layers.
So it duplicates all pageItems into one single layer.
How can i duplicate the entire Document as is with same layers and pageItems structure?
thanks

Answer 1

You would have to use recursion in that case.
Here is a short (and incomplete) example of how to iterate through all the pageItems in all the layers. Be careful with recursion, because you could run out of memory if your document is enormous. I've put in a counter that limits the recursive steps to 5,000, but you can experiment.
var doc = app.activeDocument;
var docLayers = doc.layers;
var maxSteps = 5000;
var stepsSoFar = 0;
function walkLayers(aLayerArray) {
    if (stepsSoFar < maxSteps) {
        stepsSoFar++;
        for (var i=0; i<aLayerArray.length; i++) {
            // create an object representing a layer state
            var aLayer = aLayerArray[i];
                // do something with aLayer
            for (var j=0; j <aLayer.pageItems.length; j++ ) {
                var pItem = aLayer.pageItems[j];
                // do something with pItem
            // if this layer has layers of its own, iterate through those
            if (aLayer.layers.length > 0) {
                walkLayers(aLayer.layers);
walkLayers(docLayers);