title: jsTree how to change ajax url and reload data
body: <pre><code>    $('#jstree_demo_div2').jstree({
          'core': {
              'data': {
                  "url": "tree.ashx?id=" + _id,
                  "dataType": "json" // needed only if you do not supply JSON headers
              }
          },
          "checkbox": {
              'visible': true,
              'keep_selected_style': false, 
          },
          "plugins": ["wholerow", "checkbox"]
      });
  </code></pre>
  
  <p>I need to change the url (or the variable <code>_id</code> will change) and then refresh data.
  But there seems to have a cache problem. </p>
  
  <p>I monitored the HTTP request, the request param <code>_id</code> didn't change. </p>
  
  <p>I've tried</p>
  
  <pre><code>'core': {
                  'data': {
                      "url": "tree.ashx?id=" + _id,
                      "cache":false, //←←←←
                      "dataType": "json" // needed only if you do not supply JSON headers
                  }
              }, 
  </code></pre>
  
  <p>and it didn't work.</p>
  
  <p>BTW, my jsTree.js version is 3.0.8.</p>