When I create some applications using Google Drive, there are often the case which is required to retrieve the file list and folder list. I had prepared the script each time for each case so far. But recently, I thought that if there is a library for retrieving the file and folder list (as a tree), it will be useful for me and other developers.
FilesApp library by Kanshi Tanaike has been around since 2018. I have to confess I wasn’t aware of this library until I read a more recent post, Retrieving Total File Sizes in Specific Folder of Google Drive using Google Apps Script. Similar to my own post on Creating a Google Drive report in Google Sheets the FilesApp library directly communicates to the Drive API, this library however goes a step further in terms of performance by using
UrlFetchApp.fetchAll to handle some asynchronous Drive API calls.
Source: GAS Library – FilesApp