How select 'real' next document?

Here is a script I wrote to open process all open document and opens a new document which a paste in a pixels layer for every open document containing the open documents current visible composite,  The script can the close all open documents but the new document that contains a layer for the documents that were open when the scrip was started,

/* ==========================================================
// 2016  John J. McAssey (JJMack) 
// Stack the open Document Visible layer composite into a new 300 DPI document
// This script is supplied as is. It is provided as freeware. 
// The author accepts no liability for any problems arising from its use.
// ======================================================= */
// enable double-clicking from Mac Finder or Windows Explorer
#target photoshop // this command only works in Photoshop CS2 and higher
// bring application forward for double-click events
app.bringToFront();
if (documents.length >= 2) { main(); }
else alert("multiple Document are not open in Photoshop");
///////////////////////////////////////////////////////////////////////////////
//                            main function                                  //
///////////////////////////////////////////////////////////////////////////////
function main() {
  var orig_ruler_units = app.preferences.rulerUnits;
  var orig_display_dialogs = app.displayDialogs;
  app.preferences.rulerUnits = Units.PIXELS; // set the ruler units to PIXELS
  app.displayDialogs = DialogModes.NO; // Set Dialogs off
  var closeDocs  = prompt("Should documents be Close without saving?", "Yes");
  var canvasSize = new Array(); // what size canvas is needed
  canvasSize=getDocDementions(); // get max width and height of open documents
  app.togglePalettes(); // toggle off palette so Photoshop will not need to update them
  var doc = app.documents.add( canvasSize[0], canvasSize[1], 300, "Stacked Opened Documents", NewDocumentMode.RGB, DocumentFill.TRANSPARENT ); // create a new document
  //for (var i=0;i<documents.length-1;i++) { // stack a layer for the open document into the new document
  for (var i=documents.length-2;i>-1;i--) { // stack a layer for the open document into the new document
  app.activeDocument = documents; // switch active document
  var layerName = app.activeDocument.name; // get document name
  app.activeDocument.selection.selectAll();           // select all
  try {app.activeDocument.selection.copy(true);} // copy composite of visible layers to clipboard
  catch (e) {try {app.activeDocument.selection.copy();} // copy composite of visible layers to clipboard
    catch (e) { } // empty 
  }
  app.activeDocument.selection.deselect(); // deselect
  app.activeDocument = documents[documents.length-1]; // switch to newly created document
  try { app.activeDocument.paste(); } // paste on composite of visible layers
  catch (e) { app.activeDocument.artLayers.add(); } // add an empty layer
  app.activeDocument.activeLayer.name=layerName; // label layer with Document name
  }
  if ( closeDocs == "Yes" ) closeAllButOne(); // close all opened document except the newly created document
  app.togglePalettes(); // toggle user's palettes back on
  app.runMenuItem(charIDToTypeID(("FtOn"))); // fit the document to the screen 
  app.displayDialogs = orig_display_dialogs; // Reset display dialogs 
  app.preferences.rulerUnits = orig_ruler_units; // reset units to original settings
  }
///////////////////////////////////////////////////////////////////////////////
//                           main function end                               //
///////////////////////////////////////////////////////////////////////////////
function getDocDementions(){
    width=0;
  height=0;
  for (var i=0;i<documents.length;i++) { // look at open document sizes
     if (documents.width > width) width=documents.width;
  if (documents.height > height) height=documents.height;
  }
  return new Array(width, height); // return width and height
  }
function closeAllButOne(){ // close all opened document except the newly created document
  while  (documents.length>1) {
  app.activeDocument = documents[0];
  activeDocument.close(SaveOptions.DONOTSAVECHANGES);
  }
  }