Get Facebook Desktop Notifications Using JavaScript

I am developing an social app for iPad. I am using WebView for social network. I want to get Facebook notification using javascript by injecting in WebView. I know how we can create desktop notification like that one. But did't know how i can get Facebook Notification using JavaScript. Please can anyone tell me Is there any method like (Observer or EventListener) that call and give me message of FB notification when Facebook send me desktop notification in browser.

Thanks