Test postMessage

index.html

<button id=testButton>TEST</button>

<script>
  testButton.onclick = () => {
    window.postMessage({
      command: "sbrowser-loggedAccount",
    });
  }
</script>

main.js

// Modules to control application life and create native browser window
const { app, BrowserWindow, WebContentsView } = require('electron')
const path = require('node:path')

function createWindow () {
  // Create the browser window.
  const mainWindow = new BrowserWindow({
    width: 1000,
    height: 800,
    webPreferences: {}
  })

  // and load the index.html of the app.
  //mainWindow.loadFile('index.html')

  const tabViewConstructorOptions = {
    webPreferences: {
      allowRunningInsecureContent: false,
      nodeIntegrationInSubFrames: false,
      preload: path.resolve(__dirname, 'preload.js'),
      webSecurity: true,
      sandbox: true,
      autoplayPolicy: 'document-user-activation-required',
      contextIsolation: true,
      nodeIntegration: false,
      spellcheck: true,
      transparent: false,
    }
  };
  const tabView = new WebContentsView(tabViewConstructorOptions);
  tabView.webContents.openDevTools({ mode: 'detach' });
  mainWindow.contentView.addChildView(tabView, 0);

  const { width, height } = mainWindow.getBounds();

  tabView.setBounds({ x: 0, y: 0, width, height });

  tabView.webContents.setUserAgent('SznProhlizec/6.99.99');
  // tabView.webContents.loadFile('index.html');
  tabView.webContents.loadURL('https://www.seznam.cz/prohlizec/vitejte');
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.whenReady().then(() => {
  createWindow()

  app.on('activate', function () {
    // On macOS it's common to re-create a window in the app when the
    // dock icon is clicked and there are no other windows open.
    if (BrowserWindow.getAllWindows().length === 0) createWindow()
  })
})

// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

package.json

{
  "name": "cold-fortune-translate-fcmoz",
  "productName": "cold-fortune-translate-fcmoz",
  "description": "My Electron application description",
  "keywords": [],
  "main": "./main.js",
  "version": "1.0.0",
  "author": "filip.mosner",
  "scripts": {
    "start": "electron ."
  },
  "dependencies": {},
  "devDependencies": {
    "electron": "35.1.4"
  }
}

preload.js

window.addEventListener('message', (event) => {
  console.log(event);
})

renderer.js

/**
 * This file is loaded via the <script> tag in the index.html file and will
 * be executed in the renderer process for that window. No Node.js APIs are
 * available in this process because `nodeIntegration` is turned off and
 * `contextIsolation` is turned on. Use the contextBridge API in `preload.js`
 * to expose Node.js functionality from the main process.
 */