I am trying to show a pop-up (alert/confirm box) with a custom message when a user refreshes a page. The reason is to alert the user that the data they entered might be lost. I have tried working with the 'beforeunload' event -> https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onbeforeunload.
It shows a dialog box specific to the browser and the message cannot be modified anymore. Is there a way to show our prompt (alert/confirm) with custom message? If there is, will it cause any security issues?