Call javascript when we close the Form

Hi all,

How can i call the javascript when we close the browser. I have a scenario where i have to save the data either the save the data by clicking on save button or close the browser.  As we know that when we close teh browser it ask for "your changes have not been saved. To stay on this page you can save your changes."

I want to call the javascript either clicked on "OK" or clicked on "Cancel".

Is this possible or not, if yes then please guide.