gistfile1.js

const St = imports.gi.St;
const Mainloop = imports.mainloop;
const PanelMenu = imports.ui.panelMenu;
const PopupMenu = imports.ui.popupMenu;
const Main = imports.ui.main;

function HelloWorldButton() {
    this._init();
}

HelloWorldButton.prototype = {
    __proto__: PanelMenu.Button.prototype,
    
    _init: function() {
        PanelMenu.Button.prototype._init.call(this, 0.0);
        let button = new St.Button({label:"Hello World"});
        let item;
        this.actor.set_child(button);
	item = new PopupMenu.PopupMenuItem("row 1");
        this.menu.addMenuItem(item);
	item = new PopupMenu.PopupMenuItem("row 2");
	this.menu.addMenuItem(item);
    },
};

function main() {
    let helloworld = new HelloWorldButton();
    Main.panel._leftBox.add(helloworld.actor);
    Main.panel._menus.addMenu(helloworld.menu);
}