what is the difference between window.unload and window.onunload

I've tested both of them and they work as expected in Opera, IE, FF and Chrome. I've searched window.unload on google and https://developer.mozilla.org/en-US/search?q=window.unload but it didn't help much. What is the difference between them or window.unload is just the older v开发者_如何学JAVAersion of window.onunload?

window.onunload is event handler. When you, or user, call window.unload, the event is triggered and window.onunload is called. So you can redefine window.onunload any way you like to, for example, display a confirmation dialog before unloading, send some data to the server of whatever else.