code: function(permissions, options) {
        if (!permissions || _.isString(permissions)) {
          if (!initialized) {
            throw "You must initialize FacebookUtils before calling logIn.";
          }
          requestedPermissions = permissions;
          return Parse.User._logInWith("facebook", options);
        } else {
          var newOptions = _.clone(options) || {};
          newOptions.authData = permissions;
          return Parse.User._logInWith("facebook", newOptions);
        }
      }
docs: Logs in a user using Facebook. This method delegates to the Facebook
  SDK to authenticate the user, and then automatically logs in (or
  creates, in the case where it is a new user) a Parse.User.
  
  @param {String, Object} permissions The permissions required for Facebook
  log in.  This is a comma-separated string of permissions.
  Alternatively, supply a Facebook authData object as described in our
  REST API docs if you want to handle getting facebook auth tokens
  yourself.
  @param {Object} options Standard options object with success and error
  callbacks.