this.$interval is not a function

The error message "this.$interval is not a function" typically occurs when using the AngularJS framework and trying to access the `$interval` service without injecting it into the controller.

To fix this error, make sure to inject the `$interval` service into your controller by adding it as a dependency:

angular.module('myApp').controller('myController', ['$interval', function($interval) {
  // controller logic here
}]);

Then you can use the `$interval` service in your controller to set up periodic tasks:

angular.module('myApp').controller('myController', ['$interval', function($interval) {
  var count = 0;
  var timer = $interval(function() {
    count++;
    console.log('Count:', count);
  }, 1000);

  // Cancel the interval when the controller is destroyed
  $scope.$on('$destroy', function() {
    $interval.cancel(timer);
  });
}]);

Note that to cancel the interval when the controller is destroyed, you should use `$scope.$on('$destroy', ...)` to listen for the `$destroy` event and call `$interval.cancel()` to stop the interval.