I have a single string value like 15,16,17 and i want to convert it as ["15","16","17"] using angular js 1.x or java script.Please help me 

My Angular js code is 

```html
<!DOCTYPE html>
<html>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js"></script>
<body>

<div ng-app="myApp" ng-controller="myCtrl">

Array items
<code style="display: block; padding: 8px;">{{selected | json}}</code>

</div>

<script>
var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {
    $scope.selected = [];
    $scope.selected = ["15","16","17"];
    $scope.existvalues=15,16,17;
    //$scope.selected=$scope.existvalues;
    /*Instead of above static code i want  assign a comma separated string  dynamic value like 
     this  $scope.existvalues=15,16,17;
     How i  convert and assign $scope.existvalues to $scope.selected array like ["15","16","17"] 
    */

});
</script>

</body>
</html>
```