angular Creating a Directive that Adds Event Listeners

<span my-draggable>Drag ME</span>

angular.module('dragModule', [])
.directive('myDraggable', ['$document', function($document) {
  return {
    link: function(scope, element, attr) {
      var startX = , startY = , x = , y = ;

      element.css({
       position: 'relative',
       border: '1px solid red',
       backgroundColor: 'lightgrey',
       cursor: 'pointer'
      });

      element.on('mousedown', function(event) {
        // Prevent default dragging of selected content
        event.preventDefault();
        startX = event.pageX - x;
        startY = event.pageY - y;
        $document.on('mousemove', mousemove);
        $document.on('mouseup', mouseup);
      });

      function mousemove(event) {
        y = event.pageY - startY;
        x = event.pageX - startX;
        element.css({
          top: y + 'px',
          left:  x + 'px'
        });
      }

      function mouseup() {
        $document.off('mousemove', mousemove);
        $document.off('mouseup', mouseup);
      }
    }
  };
}]);