Obtain files from large directory


I have a large subfolder in my /public directory, with over 20,000 files. The file names are not standardized or similar other than that they are all .mp4s.

When the user clicks a button, 1-3 new videos are loaded into an html page using template.onRender() method.

What I am stuck on is how I can pull videos from a directory without knowing their specific name? Only that I need to obtain some random video that hasn’t already been pulled.