Hi Yerra Chandra Mouli,
       May be this help you to achieve your scenario. #js
https://www.outsystems.com/forums/discussion/72352/confirmation-message-in-javascript-on-the-back-button-from-the-device/ 
      hope this solves your issue.

Hi @Yerra Chandra Mouli ,

I'm not sure how flexible you are about these two buttons shown on the pop up, but if you are good showing Ok and Cancel instead, you can simply use the confirmation button property from your back button.

If you need to a customized version, then you have to create a pop up yourself with customized buttons and call it when clicking on the Back button. 

Kind regards,

Tami

Hi Yerra,

In a reactive app, you can detect the browser's back button by registering the window's `popstate` event handler within the screen's OnReady event action flow using JS element.

Solution Source: https://www.outsystems.com/forums/discussion/92263/how-to-detect-browser-back-button-in-reactive-app/#Post395208

To learn more about window popstate event: https://developer.mozilla.org/en-US/docs/Web/API/Window/popstate_event

JS snippet:

window.addEventListener("popstate", function (event) {
  // Check if the user has navigated back
  confirm('Are you sure you want to go back to the previous page?');
});

Note: Make sure to remove the registered event when the screen is destroyed if it's no longer needed.

I hope this helps!

Kind regards,

Benjith Sam