Can I pop up a confirmation dialog when the user is closing the window in Safari/Chrome?

Question

In IE and FF, i can attach an event handler to onBeforeUnload, and by passing a string to a property of the event, the user will see a dialog asking him whether he wants to

Answer 1

StackOverflow itself uses onbeforeunload, and it works fine for me in Safari:

function setConfirmUnload(a){window.onbeforeunload=a?function(){return a}:null}