Combining 2 JPG files into layers from multiple folders

After user ran script and chose folder to be processed:

• it browses all contained folders (also the most deepest ones of them)
• if in any found folder there is less / more than two .jpg files it ignores all
• if there are also other subfolder(s) / file(s) of other type it ignores them too
• when there are exactly 2 jpg's only, or between other files / folders it opens them
• two files are compared for resolution and that with less is pasted to jpg with higher
• if a width / height of one file is bigger than other then document canvas are resized
• background is created while two jpg layers get their file names without extension
• .psd is saved in the folder where 2 jpg files are stored with a name of that folder

function FSf(sF, i) {
     sF = Folder(sF).getFiles()
     for(re = /\.jpe?g$/i; i < sF.length; i++) {
          if (sF instanceof Folder) FSf(sF, 0)
          else if((sF.parent.getFiles(re).length == 2)) {
               if ((dl = (d = documents).length) < 2
               && (re).test(String(sF))) {
                    open(sF); function sel() {
                         (sel = d[dl].selection)
                         .selectAll(), sel.copy()
                    }
                    if (dl + 1 < 2) sel(), r = d[dl].resolution
                    else {
                         if (b = d[dl].resolution <= r) sel()
                         nme = d[+b].name, d[+b].close();
                         function splt(v) {return v.split(re)[0]}
                         function iBL(v1, v2) {
                              return v1.isBackgroundLayer = v2
                         }
                         with(d[0]) {
                              iBL((lyr = layers)[0], false)
                              lyr[0].name = splt(name), paste(),
                              lyr[0].name = splt(nme), revealAll()
                              artLayers.add(), iBL(lyr[0], true)
                              saveAs(File((nme = sF.path) + '/'
                              + File(nme).name + '.psd')), close()
                         }
                    }
               }
          }
     } 
}
FSf(Folder.selectDialog('Please select top level folder'), 0)