How to teach an applet to display HTML and JS?

Question

Gnome

Let's say we have this code:

const Applet = imports.ui.applet;

function MyApplet(orientation){
    this._init(orientation);
}

MyApplet.prototype = {
    __proto__: Applet.TextApplet.prototype,

    _init: function(orientation){
  Applet.TextApplet.prototype._init.call(this, orientation);

  try{
      this.set_applet_label("<b>TEXT</b>");
  }
  catch (e){
      global.logError(e);
  }
    }
};

function main(metadata, orientation){
    let myApplet = new MyApplet(orientation);
    return myApplet;
}

Source .
How to teach an applet to display HTML and JS?