upgrde this script to subfolders

Try this. Should work.

Handles all subfolders.

// JavaScript Document  
///////////////////////////////////////////////////
function init_files(folder, mask)
    {
    try
        {
        function push_files(folder)
            {
            try
                {
                var f = folder.getFiles();
                for (var i = 0; i < f.length; i++)
                    {
                    if (f instanceof Folder) 
                        push_files(f);
                    else
                        if ( f.name.match(RegExp(mask+"$", "i")) ) files.push(f);
                    }
                f = null;
                }
            catch (e) { _alert(e); }
            }
        push_files(folder);
        }
    catch (e) { _alert(e); }
    }
///////////////////////////////////////////////////
  
var destFolder, sourceFolder, files, fileType, sourceDoc, targetFile, pdfSaveOpts;  
var i = 0;  
  
  
// Select the source folder.  
sourceFolder = Folder.selectDialog( 'Seleziona la cartella di origine');  
  
  
// If a valid folder is selected  
if ( sourceFolder != null )  
{  
    files = new Array();  
    fileType = ".psd"; 
    init_files(sourceFolder, fileType);  
  
if ( files.length > 0 )  
    {  
        // Get the destination to save the files  
        //destFolder = Folder.selectDialog( 'Select the folder where you want to save the converted .tif files.', '~' );  
        destFolder = sourceFolder;  
        for ( i = 0; i < files.length; i++ )  
        {  
            sourceDoc = app.open(files); // returns the document object  
  
  
     var docRef = sourceDoc;  
  
with (docRef) {  
  
chiusuraPesa();  
}  
  
  
}  
}  
}  
  
//////////////////////////////////////////////////////////////////  
//           Next everything is unchanged                       //
//////////////////////////////////////////////////////////////////  
  
  
function chiusuraPesa(){  
cercaShadow();  
searchSO(); //cerca style  
openSO(); //apre oggetto avanzato  
applicaVisibile(); // applica visibile, via tracciati e canali, salva e chiude l'oggetto avanzato  
salvaTiffDEF(); //salva il tiff definitivo   
  
  
}  
  
  
function cercaShadow(){  
var srcDoc = app.activeDocument;  
srcDoc.channels.removeAll();  
var layerSetRef = srcDoc.layerSets.getByName("shadow");  
//srcDoc.activeLayer = srcDoc.layers.getByName("style");  
layerSetRef.merge();  
    var layerSetRef = srcDoc.layers.getByName("shadow");  
    srcDoc.activeLayer = layerSetRef ;  
  
hasMask();//controlla se esiste una maschera di livello su shadow e in tal caso la cancella  
}  
  
  
function hasMask() {    
    var srcDoc = app.activeDocument;  
          var lm = true, pmd;    
          try {    
                    pmd = srcDoc.activeLayer.layerMaskDensity;    
                    srcDoc.activeLayer.layerMaskDensity = 50.0;    
                    srcDoc.activeLayer.layerMaskDensity = pmd;    
          } catch(e) { lm = false };    
  
  
          if (lm == true) {  
               function sTT(v) {return stringIDToTypeID(v)}    
    
                (ref = new ActionReference()).putEnumerated    
                (sTT('channel'), sTT('channel'), sTT('mask'));    
                (dsc = new ActionDescriptor()).putReference(sTT('null'), ref)    
                executeAction(sTT('select'), dsc);    
                    
                  var idDlt = charIDToTypeID( "Dlt " );  
                    var desc110 = new ActionDescriptor();  
                    var idnull = charIDToTypeID( "null" );  
                        var ref49 = new ActionReference();  
                        var idChnl = charIDToTypeID( "Chnl" );  
                        var idOrdn = charIDToTypeID( "Ordn" );  
                        var idTrgt = charIDToTypeID( "Trgt" );  
                        ref49.putEnumerated( idChnl, idOrdn, idTrgt );  
                    desc110.putReference( idnull, ref49 );  
                    var idAply = charIDToTypeID( "Aply" );  
                    desc110.putBoolean( idAply, true );  
                executeAction( idDlt, desc110, DialogModes.NO );  
          }  
};    
function searchSO(){  
var srcDoc = app.activeDocument;  
srcDoc.activeLayer = srcDoc.layers.getByName("style");  
}  
  
  
function openSO (){  
var idplacedLayerEditContents = stringIDToTypeID( "placedLayerEditContents" );  
    var desc7 = new ActionDescriptor();  
executeAction( idplacedLayerEditContents, desc7, DialogModes.NO );  
}  
  
  
function applicaVisibile(){  
var newLayer = activeDocument.artLayers.add();  
var idMrgV = charIDToTypeID( "MrgV" );  
    var desc3 = new ActionDescriptor();  
    var idDplc = charIDToTypeID( "Dplc" );  
    desc3.putBoolean( idDplc, true );  
executeAction( idMrgV, desc3, DialogModes.NO );  
  
var newDoc = app.activeDocument;  
  
newDoc.activeLayer.name = "Complete";  
    var quota = "quota";  
  
var layName = newDoc.activeLayer.name;   
var l = Number(newDoc.layers.length)+1;    
while(--l){    
if(newDoc.layers[l-1].name!=layName && newDoc.layers[l-1].name!=quota){    
newDoc.layers[l-1].remove();    
}    
else{continue;}    
}    
  
newDoc.pathItems.removeAll();  
newDoc.channels.removeAll();  
  
newDoc.save();  
newDoc.close();  
}  
  
  
function salvaTiffDEF(){  
  
tiffFile = new File(activeDocument.path + "/" + activeDocument.name )  
tiffSaveOptions = new TiffSaveOptions()  
TiffSaveOptions.embedColorProfile = true  
TiffSaveOptions.layers = true  
TiffSaveOptions.imageCompression = TIFFEncoding.TIFFLZW  
app.activeDocument.saveAs(tiffFile, tiffSaveOptions, true, Extension.LOWERCASE)  
app.activeDocument.close(SaveOptions.DONOTSAVECHANGES);  
}