Skip batch step via Javascript

Hi There

I'm working with Acrobat Pro DC.

I've got the following problem:

There is a process at our company witch creates multiple PDF-Files (Sometimes over 300).

In most cases this is the end of the story.

But: Sometimes i have to convert all of them to PDF 1.4  (Acrobat5.x).

I wanted to generate an action for the conversion:

1. Open all files in the folder
2. If it is a PDF
   1. Save as PDF 1.4
3. Leave every other file alone.

In Acrobat DC i found no option to only load pdf files in the actions wizard.

My Attempt was to insert a javascript between opening and saving:

     /* Geben Sie hier den Titel des Skripts ein */

     var myFilename = this.documentFileName;

     var myRegExp = /\.pdf/;

          if(myRegExp.test(myFilename)) {

                 // Do nothing

          } else {

                 // Skip saving and proceed with next file in the folder

          }