How to handle callback in angularjs?

You want to return your $http request from registerUser which can then be used in your controller in the same way you are using it in the service.

Controller:

registerUser.registerUser().success(function(data, status, headers, config){   //This code will now execute when the $http request has resolved with a success   if($rootScope.success){      $location.path('/confirm');   }}).error(function(error, status, headers, config){   //An error occurred in $http request   console.log(error); });

Service:

this.registerUser = function(){    $ionicLoading.show();    return $http({        method: 'POST',        datatype:'json',        data:{obj:$rootScope.registration},        url: 'http://localhost/LoginService.asmx/CreateUser',        contentType: "application/json; charset=utf-8",        cache: false    }).success(function (data, status, headers, config){        if (status == '200') {            var obj = data;            $rootScope.success = true;            $ionicLoading.hide();            //alert(obj);        }    }).error(function (data, status, headers, config){        $ionicLoading.hide();    });};

A few things worth noting...

You are returning from a service which is not required, a service works as an instance and so the instance is already injected. It is a factory (singleton) that requires a return.

You are setting $scope.registration to be the same as $rootScope.registration and then setting $rootScope.registration to be the same as $scope.registration in your getEnterGeneratedCode function which is unnessasary and should be prototypicaly inherited anyway.

You should always try to defined depedencys with like so:

.controller('RegisterAccountCtrl', ['$scope', '$rootScope', 'registerUser', '$location', function($scope, $rootScope, registerUser, $location){}]);

Unless $rootScope.success is being used elsewhere its currently pointless to set and I would recommend avoiding setting props on your $rootScope as it can quickly get out of control.

Here is a simplified version of your code:

.controller('RegisterAccountCtrl', [    '$scope',    '$rootScope',    'registerUser',    '$location',function($scope, $rootScope, registerUser, $location) {    $scope.getEnterGeneratedCode = function() {        $ionicLoading.show();        registerUser.registerUser().success(function(data, status, headers, config) {            if (status == '200') {                var obj = data;                $ionicLoading.hide();                $location.path('/confirm');                //alert(obj);            }        }).error(function(data, status, headers, config) {            $ionicLoading.hide();        });    }}]).service('registerUser', [    '$http',    '$rootScope',    '$ionicLoading',function($http, $rootScope, $ionicLoading) {    this.registerUser = function() {        return $http({            method: 'POST',            datatype: 'json',            data: {                obj: $rootScope.registration            },            url: 'http://localhost/LoginService.asmx/CreateUser',            contentType: "application/json; charset=utf-8",            cache: false        });    };}]);

Use a promise - see changes below:

.controller('RegisterAccountCtrl', function ($scope,$rootScope,registerUser,$location) {    $rootScope.success = false;    $scope.registration = $rootScope.registration;$scope.getEnterGeneratedCode = function(){        $rootScope.registration = $scope.registration;        registerUser.registerUser().then(function() {          $location.path('/confirm');        })}

And inside service

.service('registerUser',function($http,$rootScope,$ionicLoading){    this.registerUser = function(){        $ionicLoading.show();        // Return a promise        return $http({            method: 'POST',            datatype:'json',            data:{obj:$rootScope.registration},            url: 'http://localhost/LoginService.asmx/CreateUser',            contentType: "application/json; charset=utf-8",            cache: false        }).success(function (data, status, headers, config){            if (status == '200') {                var obj = data;                // Don't need now - $rootScope.success = true;                $ionicLoading.hide();                //alert(obj);            }        }).error(function (data, status, headers, config){            $ionicLoading.hide();        });    }; return this;})