// configuration
var exportExtension = "jpg"; // extension jpg or png
var exportPath = "/Users/kasparsj/Work/someproject/images"; // set to your project path

app.preferences.RulerUnits = Units.PIXELS;
var doc = app.activeDocument;
var html = '';
var exportOptions = new ExportOptionsSaveForWeb();
exportOptions.quality = 80; // set quality
if (exportExtension == "jpg") {
  exportOptions.format = SaveDocumentType.JPEG;
}
else {
  exportOptions.format = SaveDocumentType.PNG;
}

// do it!
processLayerSet(doc);

// loops trough all layers and processes visible Art Layers
function processLayerSet(layer) {
  for (var i=0; i<layer.layerSets.length; i++) {
    if (layer.layerSets[i].visible) {
      processLayerSet(layer.layerSets[i]);
    }
  }

  for (i=0; i<layer.artLayers.length; i++) {
    if (layer.artLayers[i].visible) {
      processArtLayer(layer.artLayers[i], i);
    }
  }
}

function processArtLayer(layer, index) {
  // copy layer
  doc.activeLayer = layer;
  doc.selection.deselect();
  doc.selection.selectAll();
  doc.selection.copy();
  // create new doc, paste and crop
  var newDoc = app.documents.add(1920, 1080, 72, layer.name);
  newDoc.paste();
  newDoc.selection.selectAll()
  intersectSelectionWithTransparency()
  newDoc.crop(newDoc.selection.bounds)
  // save new doc
  newDoc.exportDocument(new File(exportPath+"/"+layer.name+"."+exportExtension), ExportType.SAVEFORWEB, exportOptions);
  newDoc.close(SaveOptions.DONOTSAVECHANGES);
}

function intersectSelectionWithTransparency(){
  var desc = new ActionDescriptor();
  var ref = new ActionReference();
  ref.putEnumerated( charIDToTypeID( "Chnl" ), charIDToTypeID( "Chnl" ), charIDToTypeID( "Trsp" ) );
  desc.putReference( charIDToTypeID( "null" ), ref );
  var ref1 = new ActionReference();
  ref1.putProperty( charIDToTypeID( "Chnl" ), charIDToTypeID( "fsel" ) );
  desc.putReference( charIDToTypeID( "With" ), ref1 );
  executeAction( charIDToTypeID( "Intr" ), desc, DialogModes.NO );
}