class WinButton { render() { console.log("Win Button"); } }
class MacButton { render() { console.log("Mac Button"); } }
class WinCheckbox { render() { console.log("Win Checkbox"); } }
class MacCheckbox { render() { console.log("Mac Checkbox"); } }

class WinFactory {
  createButton() { return new WinButton(); }
  createCheckbox() { return new WinCheckbox(); }
}
class MacFactory {
  createButton() { return new MacButton(); }
  createCheckbox() { return new MacCheckbox(); }
}

// Client
const factory = new MacFactory();
const button = factory.createButton();
const checkbox = factory.createCheckbox();
button.render(); checkbox.render();