Attaching events - basic combo dynamic data load

EDIT | I think I figure it out. I looked at an example of JetView event handling and voila! My bad. Can’t seem to delete posts so I guess this is staying.

Trying to attach a focus event handler to a combo, so I can hopefully populate the options dynamically (only when selected the first time).

I have this basic code:

import {JetView} from "webix-jet";

export default class LayoutView extends JetView {
    config() {

        var ui = {
            "view": "form",
            "rows": [
                {
                    "cols": [
                        {
                            id: "complex",
                            view: "combo",

                            "placeholder": "Complex",
                            //"options": '/complex',

                            "height": 0,

                            //onfocus: function() {
                            //    alert('asdasd');
                            //}
                        },
                    ],
                    "height": 65
                }
            ]
        };

        $$("complex").attachEvent("onFocus", function(current_view, prev_view){
            alert('asdasd');
        });

        return ui;
    }
}

I am getting this JS error:

Cannot read property ‘attachEvent’ of undefined