The Typescript definitions for Kendo UI define the kendo.ui.ToolBarOpenEvent as follows:
interface ToolBarEvent {
sender: ToolBar;
preventDefault: Function;
isDefaultPrevented(): boolean;
}
interface ToolBarOpenEvent extends ToolBarEvent {
SplitButton?: JQuery | undefined;
}
The event is also documented that way in https://docs.telerik.com/kendo-ui/api/javascript/ui/toolbar/events/open. However, the corrersponding method in kendo-toolbar.js:446-453 does the following:
open: function (e) {
var isDefaultPrevented = that.toolbar.trigger(OPEN, { target: element });
if (isDefaultPrevented) {
e.preventDefault();
return;
}
that.adjustPopupWidth(e.sender);
},