use explicit running header name + jquery's toggle

IPython/html/static/tree/js/kernellist.js

@@ -1,45 +1,41 b''
 //----------------------------------------------------------------------------
 //  Copyright (C) 2014  The IPython Development Team
 //
 //  Distributed under the terms of the BSD License.  The full license is in
 //  the file COPYING, distributed as part of this software.
 //----------------------------------------------------------------------------
 
 //============================================================================
 // Running Kernels List
 //============================================================================
 
 var IPython = (function (IPython) {
     "use strict";
 
     var utils = IPython.utils;
 
     var KernelList = function (selector, options) {
         IPython.NotebookList.call(this, selector, options, 'running');
     };
 
     KernelList.prototype = Object.create(IPython.NotebookList.prototype);
 
     KernelList.prototype.sessions_loaded = function (d) {
         this.sessions = d;
         // clear out the previous list
         this.clear_list();
         var item;
         for (var path in d) {
             item = this.new_notebook_item(-1);
             this.add_link('', path, item);
             this.add_shutdown_button(item,this.sessions[path]);
         }
        
-        if ($.isEmptyObject(d)) {
-           $('#' + this.element_name + '_list_header').show();
-       } else {
-           $('#' + this.element_name + '_list_header').hide();
-       }
+        $('#running_list_header').toggle($.isEmptyObject(d));
     }
     
     IPython.KernelList = KernelList;
 
     return IPython;
 
 }(IPython));