jQuery: alert box when leaving the site

gistfile1.txt

// If the link being clicked is external the user will be prompted
// to confirm they wish to leave the site. Confirmation results in 
// the external link being opened in a new window
        $('a')
            .bind('click', function(event) {

            var a = new RegExp('/' + window.location.host + '/');

            if(!a.test(this.href)) {

                event.preventDefault();

                var confirmLeave = confirm("You are now leaving the site.");

                if(confirmLeave) {
                    window.open(this.href, '_blank');
                }
            }
        });