jQuery("#thetree").jstree({
        "json" : {
      "data": [{"data":'Kit 1',"attr":{"id":'kit1'}}],
            "ajax": {
        "type": "GET",
        "url": function (node) {
          var nodeId = node.attr('id');
          return 'your_json_url/pid=' + nodeId;
        },
                "data": {"action": 'getChildren'},
        "success": function (new_data) {
            return new_data;
        },
        "error" : function(e) {
          console.log("ajax failed");
        }
            }
        },
        "plugins" : [ "themes", "json", "ui", "cookies" ]
    });