javascript - How to open files at a Interval of some of number

I have a folder in which there are some files and i want to open those files in Photoshop but not at once . Let say there are more than 20 files in a folder so i want to open 20 files at once and do something with those files and then remaining files will open and again do something with those files.
I'm making a script for Photoshop using JavaScript so please help me... thank you