kintone customize with es6

kintone-create-edit-show.js

import jQuery from "jquery";
(() => {
    const events = [
        "app.record.create.show",
        "app.record.edit.show",
    ];
    kintone.events.on(events, (ev) => {
        const el = kintone.app.record.getHeaderMenuSpaceElement();
        const hello = "hello";
        const world = "world!";
        const message = {
            hello,
            world,
        };
        const copied = Object.assign({}, message);
        jQuery(el).append(`<div>${copied.hello} ${copied.world}!</div>`);
    });
})();