This is like running the ls Linux command for listing all the files and their details in a particular Google Drive folder. You an even make a tree of files.

Call the listFiles method with the Drive folder name and it will create a list of all files and appends them to a spreadsheet. The direct download links are particularly handy for downloads PDFs and other non Google Docs documents.

function listFilesInFolder(folderName) {
  var folder = DriveApp.getFoldersByName(folderName).next();
  var contents = folder.getFiles();

  var file,
    data,
    sheet = SpreadsheetApp.getActiveSheet();
  sheet.clear();

  sheet.appendRow(['Name', 'Date', 'Size', 'URL', 'Download', 'Description', 'Type']);

  for (var i = 0; i < contents.length; i++) {
    file = contents[i];

    if (file.getFileType() == 'SPREADSHEET') {
      continue;
    }

    data = [
      file.getName(),
      file.getDateCreated(),
      file.getSize(),
      file.getUrl(),
      'https://docs.google.com/uc?export=download&confirm=no_antivirus&id=' + file.getId(),
      file.getDescription(),
      file.getFileType().toString(),
    ];

    sheet.appendRow(data);
  }
}