javascript - What is the first parameter in Parse.User.signUp()? -

i'm using parse.com database of app , signup view, i'm trying reduce number of lines in code.

user.set("username",$scope.user.email); user.set("email",$scope.user.email); user.set("password",$scope.user.password);     user.signup(null,         { success: function(user) {              $ionicloading.hide();              $scope.state.success = true;         }, error: function(user, error) {             $ionicloading.hide();             if (error.code == 125) { $scope.error.message = "please specify valid email address"; }             else if (error.code == 202) { $scope.error.message = "the email address registered"; }             else { $scope.error.message = error.message; }             $scope.$apply();         }     }); 

my question this: first parameter supposed be? on parse.com, not use examples first parameter null (that have seen). , cannot find docs explain .signup() method detail.

my instinct tells me parameter expects user data in json format. don't know sure.

edit: solution:

var user = new parse.user(); user.signup({      "username": $scope.user.email,     "email": $scope.user.email,      "password": $scope.user.password  }, {      success: function(user)      {   $ionicloading.hide();          $scope.state.success = true;     },      error: function(user, error)      {   $ionicloading.hide();         if (error.code == 125) { $scope.error.message = "please specify valid email address"; }         else if (error.code == 202) { $scope.error.message = "the email address registered"; }         else { $scope.error.message = error.message; }         $scope.$apply();     } }); 

from parse sdk docs:

signup(attrs, options) 

attrs attributes add user, or null.