How to debug widget not starting?

I'm trying to use basic widget example from Bangle.js Widgets.

Using it in IDE with this works:

WIDGETS = {}; 
(() => {
  function draw() {
    g.reset();
    g.drawString("X", this.x, this.y);
  }

  WIDGETS["mywidget"] = {
    area: "tl",
    width: 28,
    draw: draw
  };
})()
Bangle.drawWidgets();

But when I remove first/last lines and upload resulting code to Bangle.js 2 using my local copy of https://banglejs.com/apps the widget is not loaded.

How can I debug why it is not loaded?