How to capture requests from <iframe> in Electron window

main.js

/*
 * By default, the Electron (or underlying Chrome instance, to be more precise) will not allow
 * javascript communication between parent window and an <iframe>. Which makes it hard to cover
 * scenarios when you want to do something after an action has been performed inside the <iframe>.
 * This example shows how to react on web reqest from within <iframe>.
 *
 * The 'onBeforeRequest' listener is documented here:
 * http://electron.atom.io/docs/api/session/#webrequestonbeforerequestfilter-listener 
 */

app.on('ready', () => {
  let myWindow = new BrowserWindow({
    width: 800,
    height: 800,
    center: true
  });
  
  // Listen to all requests in order to catch the one you want to react to. For example on
  // link click, form submit, etc.
  // This hack is needed, because it's otherwise not possible to react to javascript events
  // within an <iframe> due to browser security/sandboxing when iframe url is on different domain.
  myWindow.webContents.session.webRequest.onBeforeRequest({}, (details, callback) => {
    if (details.url.endsWith('/actions/submit/')) {
      // do your stuff ...
      
      // ... for example, block the submit
      callback({ cancel: true });
      myWindow.close();
      
      // ... or open new electron window, etc.
    }
    callback({ cancel: false });
  });
  
  // replace with whatever html you want to load in your electron window
  myWindow.loadURL(`file://${__dirname}/index.html`);
});