Execute function before refresh

Question

On my HTML page, when the user clicks / presses F5 button the page refreshes, but before it refreshes I want to execute a function or a simple alert.

Use

Answer 1

$(window).bind('beforeunload', function(){
    return '>>>>>Before You Go<<<<<<<< \n Your custom message go here';
});

Source: http://www.mkyong.com/jquery/how-to-stop-a-page-from-exit-or-unload-with-jquery/

Demo: http://www.mkyong.com/wp-content/uploads/jQuery/jQuery-stop-page-from-exit.html