code: function login(options) {
  
      // Return promise and resolve once user info is retrieved.
      return new Promise(function (resolve, reject) {
  
        FB.login(function (response) {
  
          /*response = authResponse + status*/
          _getUser(response).then(function (userResponse) {
  
            if(userResponse.user) {
  
              /*userResponse = authResponse + status + user*/
              resolve(userResponse);
  
            } else {
  
              // Reject login promise if the user canceled the FB login.
              reject(userResponse);
  
            }
  
          });
  
        }, options);
  
      });
    }
docs: Invoke standard Facebook login popup, using specified options.