Why $scope doesn't change in the alert box? (angularJS) -

i'am trying understand behaviour: when change input view change when click on button alert box don't change $scope.firstname. give me advices. regards

var app = angular.module('myapp', []);  app.controller('myctrl', function($scope) {      $scope.firstname = "john";      $scope.lastname = "doe";      var test=$scope.firstname;      $scope.test=function(){    	      	alert(test);    	      };  });

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>  <div ng-app="myapp" ng-controller="myctrl">      first name: <input type="text" ng-model="firstname"><br>      last name: <input type="text" ng-model="lastname"><br>      full name: {{firstname + " " + lastname}}      <button ng-click="test()">click</button>  </div>

currently, when launch controller, doing 3 things :

$scope.firstname = "john"; $scope.lastname = "doe"; var test=$scope.firstname; 

so var test initialize when launch controller not when laucnh function. funtion, print value.

if want print current version of scope, need :

var app = angular.module('myapp', []); app.controller('myctrl', function($scope) {   $scope.firstname = "john";   $scope.lastname = "doe";    $scope.test=function(){            alert($scope.firstname);           };  });