app.js

const { app, BrowserWindow, TouchBar } = require('electron');
const { TouchBarLabel, TouchBarButton, TouchBarSpacer } = TouchBar;

const button = new TouchBarButton({
  label: `Count: ${counter}`,
  accessibilityLabel: 'Counter',
  backgroundColor: '#6ab04c',
  click: () => {
    update();
  },
});

let counter = 0;

const update = () => {
  counter += 1;
  button.label = `Count: ${counter}`;
};

const touchBar = new TouchBar({
  items: [
    button,
  ],
});

function createWindow () {
  // Create the browser window.
  let win = new BrowserWindow({
    width: 800,
    height: 600,
    webPreferences: {
      nodeIntegration: true
    }
  })

  // and load the index.html of the app.
  win.loadFile('index.html');
  win.setTouchBar(touchBar);
}

app.whenReady().then(createWindow)