AngularJS data binding with expression

Angular data binding with the source as an expression

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.5/angular.min.js"></script>
<body ng-app="SampleMVCApp">
    <div ng-controller="SampleController">
         <h2>{{getText}}</h2>
         <input type='button' ng-click='changeText()'>
    </div>
</body>

JavaScript

angular.module("SampleMVCApp", [])
    .controller("SampleController", function ($scope) {
    $scope.getText ='hi1';
    $scope.changeText=function(){
     $scope.getText ='hi2';
    }
});