Flutter Web – Set the EventListener to other tab and get the Title and details from it using javascript

First, I will explain what I want to do. I am trying to open the payment gateway url from my flutter web app using html.window. I am able to open the link in next tab and also done the all payment to success. Now, for giving the payment status to my web app back, I am checking the title of that payment gateway tab that contains status and transaction id. But I am unable to do this.

Here is the flutter code first:-

 void openURLAndListen(String url)async {
  js.context.callMethod('openURLAndListen', [url]);

    // Wait for a brief duration to ensure JavaScript function execution
    await Future.delayed(const Duration(microseconds: 500));
   
    html.window.addEventListener('PAGE_LOADED', (event){
    MessageEvent event2 = event as MessageEvent;
    print("Get Message from js ${event2.data}");
  });
    
  }

Here is the Javascript function :-

function openURLAndListen(url) {
    var openedWindow = window.open(url, '_blank');

    openedWindow.onload = function(){

// Get the title of the page
        var titles = [];
            var tabs = document.querySelectorAll('title');
            tabs.forEach(function(tab) {
                titles.push(tab.innerText);
            });
            // Notify Flutter app with the page title
            window.parent.postMessage({ type: "PAGE_LOADED", titles: titles }, url);
    }

}

This javascript file was called in index.xml file in web folder.

Please give me the proper solution for this, correct me if the function is not correct.

I had tried to use addEventListener to call the title details on opened window.