This looks at an arbitrary directory, looks for any folders inside that directory, and recursively looks for files older than 'Days'. I use this to clean out a directory of security camera video.

DirectoryClean.gs

/* 
Version 1.0.1
Updated 03/19/2018

This looks at an arbitrary directory, looks for any folders inside that directory, and recursively looks for files older than 'Days'.
I use this to clean out a directory of security camera video. 

To configure, set the folderID and the Days. 

Michael Bierman 
with thanks to Tim Garrett. 
*/ 


function findAllFolders() {
    Logger.clear()
    /* Edit the folderID for the parent folder you want to monitor */
    var folderId = "0BzROkcV_RG8kQTlrOVVWUEdvajQ";
    var Days = 30 * 24 * 60 * 60 * 1000;
    var parentFolder = DriveApp.getFolderById(folderId);
    var childFolders = parentFolder.getFolders();

 
  
  while (childFolders.hasNext()) {
     var folder = childFolders.next();
       Logger.log( '<<<<<<<< %s >>>>>>>>', folder);
     var files = folder.getFiles();
     
     while (files.hasNext()) {
       var fileName = files.next();
 //    var fileId = fileName.getId();
       var fileDate = fileName.getDateCreated();
     
       if (new Date() - fileName.getLastUpdated() > Days) {
         Logger.log('DELETING! %s', fileName);
           /* Deleting file */
         fileName.setTrashed(true);
       }
       else {
         Logger.log('ignoring %s...', fileName);
       }
    }
    Logger.log("");
   }
    Logger.log('End of run.');
}