AngularJs Check if a key exists in an object

<!DOCTYPE html>
<html lang="en">
<head>
 <script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.2.13/angular.min.js"></script>
 <script>
 var myApp = angular.module("myApp", []);
 myApp.controller("myController", function($scope) {
 
  $scope.obj1 = {"key1":99};
  $scope.result = '';
  $scope.textvalue = "key1";
  $scope.checkKey = function() {
  var txtVal = $scope.textvalue;
  if(!(txtVal in $scope.obj1)){
  $scope.result = "Key not Found.";
  }else{
   $scope.result = "Key Exists in Object obj1.";
  }
  }
});
</script>
</head>
<body>  
<div ng-app="myApp">  
<div ng-controller="myController">  
    <input type="text" ng-model="textvalue" ><br>
    <button ng-click ="checkKey()" >Check Key Exists</button>
	<br>
	Result = {{result}}<br>
</div> 
</div>
</body>  
</html>