How to add custom message while refreshing crome browser

Trying this code for alert message on refreshing the crome browser

@HostListener("window:beforeunload", ["$event"])
unloadHandler(event: Event) {
    let result = confirm("Changes 
    you made may not be saved.");
    if (result) {
      // Do more processing...
    }
    event.returnValue = false; // 
    stay on same page
}