Filtering

<input id="dropdowntree"/>

<script>
$("#dropdowntree").kendoDropDownTree({
  dataSource: [{ text: "item1", value: 1 }, { text: "item2", value: 2 }],
  filter: "startswith",
  filtering: function(e) {
      //get filter descriptor
      var filter = e.filter;

      // handle the event
  }
});
</script>

<input id="dropdowntree"/>

<script>
function dropdowntree_filtering(e) {
  //get filter descriptor
  var filter = e.filter;

  // handle the event
}
$("#dropdowntree").kendoDropDownTree({
  dataSource: [{ text: "item1", value: 1 }, { text: "item2", value: 2 }],
  filter: "startswith"
});
var dropdowntree = $("#dropdowntree").data("kendoDropDownTree");
dropdowntree.bind("filtering", dropdowntree_filtering);
</script>

<input id="dropdowntree"/>

<script>
$("#dropdowntree").kendoDropDownTree({
  dataSource: [{ text: "item1", value: 1 }, { text: "item2", value: 2 }],
  filter: "startswith",
  filtering: function(e) {
      var filter = e.filter;

      if (!filter.value) {
        //prevent filtering if the filter does not have value
        e.preventDefault();
      }
  }
});
</script>