exporting selected objects to dxf

I have tried everything to write a script and I cant.  I am not experienced but I copied and pasted with no luck.  can anyone help.  all I need is to quickly export selected objects with one click to a temp folder

here is what I have

try {
if (app.documents.length > 0 ) {

  var destFolder = null;
  destFolder = Folder.selectDialog( 'Select folder for dxf files.', '~' );
  
  if (destFolder != null) {
   var options, i, sourceDoc, targetFile; 

   options = this.getOptions();
       
      for ( i = 0; i < app.documents.length; i++ ) {
       sourceDoc = app.documents; // returns the document object
        
 
    targetFile = this.getTargetFile(sourceDoc.name, '.dxf', destFolder);
  
    sourceDoc.exportFile(targetFile, ExportType.dxf, options);
   }
   alert( 'Documents exported as dxf' );
  }
}
else{
  throw new Error('There are no document open!');
}
}
catch(e) {
alert( e.message, "Script Alert", true);
}

var exportOptions = new ExportOptionsAUTOCAD(); {
var type = ExportType.DXF; 
var file = new File(folder.fsName+"/"+layer.name+".DXF");
                    document.exportFile(file, ExportType.DXF, options);
   exportAutoCADOptions.exportFileFormat = AutoCADExportFileFormat.DXF;  // AutoCADExportFileFormat.DWG   DXF 
  exportAutoCADOptions.exportOption = AutoCADExportOption.PreserveAppearance;  //PreserveAppearance MaximumEditability 
   exportAutoCADOptions.version = AutoCADCompatibility.AutoCADRelease14; 
   exportAutoCADOptions.exportSelectedArtOnly = false; 
   exportAutoCADOptions.convertTextToOutlines = false; 
   exportAutoCADOptions.unit = AutoCADUnit.Millimeters; 
        app.activeDocument.exportFile( fileSpec, type, exportOptions ); 
     return options;
}

/** Returns the file to save or export into.
@9397041 docName the name of the document to be saved or exported
@9397041 ext the extension the file extension to be applied
@9397041 destFolder the output folder
@Return File object
*/
function getTargetFile(docName, ext, destFolder) {
var newName = "";

if (docName.indexOf('.') < 0) {
  newName = docName + ext;
} else {
  var dot = docName.lastIndexOf('.');
  newName += docName.substring(0, dot);