[help] Open files from a folder in pairs

Hello,

I have developed a .jsx file which combines two opened files in Photoshop into one and rearranges them accordingly, saves copies into a new folder and then closes the two open documents out of Photoshop.

The only thing I am unable to (don't know how to) do is select a folder which only will show png/tiff/psd files and run the script on all the files selected in the folder two at a time.

I am very very new to javascripting, and I am still learning a lot about it, but I am completely confused on how to get a function to loop through files in a folder in pairs.

If anyone is able to help me with this problem or point me in the right direction, it would be greatly appreciated.