Custom beforeunload prompt with javascript

I'm trying to setup an exit survey so that when a user leaves our checkout page they are prompted asking them why they're leaving.

Is this possib开发者_运维问答le?

I've spent some time on Google but it appears as though the only solution is a simple browser-controlled confirm-like prompt. Is this true?

update

The following confirm dialog never appears, the page just changes or exits. How can I prevent the page from changing/exiting until I wait for a user's response. I guess I should ask, how can I resume a user's exit/page change action after using e.preventDefault(); ?

jQuery(window).bind('beforeunload', function() {
    return function () {
        alert('x');

        setTimeout(50000, function () {
            confirm('you sure?');
        });
    }();
});

If you are using jQuery you can just do

$(window).unload( function() {
  //statements
});

You can do anything you want in the onunload event of the browser:

body.onunload = function() {
  foo();
  bar();
}

As suggested by levu, use the onunload event in combination with a custom modal dialog, such as thickbox - http://jquery.com/demo/thickbox/