如何使AngularJs指令在特定屏幕大小

Question

我有这个指令，当我滚动页面时，它会向标题部分添加和删除一个类，一个隐藏/显示标题。我希望此指令仅适用于小于600px的屏幕尺寸。任何帮助将不胜感激。

我的角度指令

.directive('scrollClass', function ($window) {
    return {
      restrict: 'A',
      link: function (scope, element) {
        var current;
        current = $window.pageYOffset;
        angular.element($window).on('scroll', function () {
            var ref;
            if ($window.innerHeight + $window.pageYOffset >= document.body.offsetHeight) {
                scope.scrolled = false;
            } else {
                scope.scrolled = (ref = this.pageYOffset > current) != null ? ref : { 'true': false };
            }
            current = this.pageYOffset;
            return scope.$apply();
        });
      }
    };
  })

我的HTML元素

<header class='top-menu' ng-class='{ "scrolled" : scrolled }' scroll-class=''>