AngularJS Call JavaScript function and Update element

Use ngclick Function

<div ng-app="myApp" ng-controller="myCtrl">
    <h1 ng-click="changeName()">{{firstname}}</h1>
</div>

<script>

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.firstname = "John";
    $scope.changeName = function() {
        $scope.firstname = "Nelly";
    }
});

</script>