Подключаем

script src="../lib/login.service.js"></script>
<script src="../lib/drive.service.js"></script>

Инициализируем

var SCOPES = 'https://www.googleapis.com/auth/drive.file'
      var CLIENT_ID = 'YOUR CLIENT ID';
      DISCOVERY_DOCS = ['https://www.googleapis.com/discovery/v1/apis/drive/v3/rest'];
      window.loginService = new LoginService(CLIENT_ID, SCOPES, DISCOVERY_DOCS);

И используем методы initClient, signIn, signOut, userProfile, saveFile, loadFile, listFiles
https://github.com/vitogit/gDriveSync.js