How can I override the OnBeforeUnload dialog and replace it with my own?

Question

I need to warn users about unsaved changes before they leave a page (a pretty common problem).

window.onbeforeunload=handler

This works bu

Answer 1

I faced the same problem, I was ok to get its own dialog box with my message, but the problem I faced was : 1) It was giving message on all navigations I want it only for close click. 2) with my own confirmation message if user selects cancel it still shows the browser's default dialog box.

Following is the solutions code I found, which I wrote on my Master page.

function closeMe(evt) {
    if (typeof evt == 'undefined') {
        evt = window.event; }
    if (evt && evt.clientX >= (window.event.screenX - 150) &&
        evt.clientY >= -150 && evt.clientY <= 0) {
        return "Do you want to log out of your current session?";
    }
}
window.onbeforeunload = closeMe;