Проверьте значение текстового блока на значение ng-change == в угловой

<script>
  angular.module('changeExample', [])
    .controller('ExampleController', ['$scope', function($scope) {
      $scope.evaluateChange = function(obj,$event) {
        var currentElement = $event.target;
        console.log(currentElement.value);//this will give you value of current element
      };
    }]);
</script>

<div ng-controller="ExampleController">
  <textarea ng-change="evaluateChange(this)" id="ng-change-example1"></textarea>
</div>
Ankur