/**
   * Created by hekangjia on 16-6-8.
   */
  
  $(function () {
      $('.tree li:has(ul)').addClass('parent_li').find(' > span').attr('title', 'Collapse this branch');
      $('.tree li.parent_li > span').on('click', function (e) {
          var children = $(this).parent('li.parent_li').find(' > ul > li');
          if (children.is(":visible")) {
              children.hide('fast');
              $(this).attr('title', 'Expand this branch').find(' > i').addClass('icon-plus-sign').removeClass('icon-minus-sign');
          } else {
              children.show('fast');
              $(this).attr('title', 'Collapse this branch').find(' > i').addClass('icon-minus-sign').removeClass('icon-plus-sign');
          }
          e.stopPropagation();
      });
  });