code: function(user, permissions, options) {
        if (!permissions || _.isString(permissions)) {
          if (!initialized) {
            throw "You must initialize FacebookUtils before calling link.";
          }
          requestedPermissions = permissions;
          return user._linkWith("facebook", options);
        } else {
          var newOptions = _.clone(options) || {};
          newOptions.authData = permissions;
          return user._linkWith("facebook", newOptions);
        }
      }
docs: Links Facebook to an existing PFUser. This method delegates to the
  Facebook SDK to authenticate the user, and then automatically links
  the account to the Parse.User.
  
  @param {Parse.User} user User to link to Facebook. This must be the
  current 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.