//Get any Google Docs in folder and add a paragraph to all of them
function example81() {
  const parentFolder = DriveApp.getFolderById('ADD FOLDER ID HERE');
  const listOfDocs = parentFolder.getFilesByType(MimeType.GOOGLE_DOCS);
  while (listOfDocs.hasNext()) {
    var file = listOfDocs.next();
    var docId = file.getId();
    var doc = DocumentApp.openById(docId);
    var body = doc.getBody();
    body.appendParagraph("This paragraph was added automatically.");
  }
}

//Delete files of a specific type that haven't been updated for over a week
function example82() {
  const parentFolder = DriveApp.getFolderById('ADD FOLDER ID HERE');
  const listOfSsheets = parentFolder.getFilesByType(MimeType.GOOGLE_SHEETS);
  while (listOfSsheets.hasNext()) {
    var file = listOfSsheets.next();
    if (new Date() - file.getLastUpdated() > 7 * 24 * 60 * 60 * 1000) {
     file.setTrashed(true);
    }
  }
}