code: function createClient(app, dataCenter, callback) {
      var client = new Client(app, dataCenter);
      if (callback) {
          client.once('connect', callback);
      }
      connect.apply(client);
      return client;
  }
docs: - **app**: are all the application info: - **id** and **hash** _(required)_: you can get it your own APP ID at https://core.telegram.org/myapp - **version** _(required)_: semver of your application, see http://semver.org - **langCode** _(required)_: device/user language, see ISO 639-1 - **deviceModel** _(required)_: the device model or the user agent - **systemVersion** _(required)_: the operative system version - **authKey** _(optional)_: the authentication key, already persisted by your app, can be supplied here. The `authKeyCreate` event will be emitted when the connection will be established, after the the `connect` event - **connectionType** _(optional)_: the value could be `HTTP` or `TCP`, HTTP is by default - **dataCenter** _(required)_: the data center address, you could use `telegramLink.TEST_PRIMARY_DC` or `telegramLink.PROD_PRIMARY_DC` - **connectionListener** _(optional)_: a callback function, it will be registered as listener on `connect` event The code: