angularjs指令的代码，看不懂，求高手解释下？

Question

angular.module('cnodejs.directives').directive(  // Collection-repeat image recycling while loading  // https://github.com/driftyco/ionic/issues/1742  'resetImg', function ($document) {    return {      restrict: 'A',      link: function($scope, $element, $attributes) {        var applyNewSrc = function (src) {          var newImg = $element.clone(true);          newImg.attr('src', src);          $element.replaceWith(newImg);          $element = newImg;        };        $attributes.$observe('src', applyNewSrc);        $attributes.$observe('ngSrc', applyNewSrc);      }    };  });