Can I get the iOS6 IDFA from Javascript?

iOS6 introduces the IDFA "Identifier for Advertising" for iOS6 devices.

Can this ID be retrieved from Javascript running in Safari on an iOS6 device ? Or is it an app-only feature ?

How do I get the IDFA?

Find My Apple Device ID The simplest way to locate your iOS device's IDFA is to use a third-party app called The Identifiers. The purpose of the app is to display a device's IDFA, so all you have to do is install and open the app to see your IDFA.

Is udid same as IDFA?

In 2012, the UDID was replaced by the IDFA to curb persistent tracking, with Google following suit the next year by releasing an advertising ID for Android to replace its unique Android ID.

Is IDFA dead?

Apple Has Killed IDFA, Dropping a Bombshell on the Mobile Ad Ecosystem.

As far as I can see, it's an app-only feature. It doesn't seem to be exposed in Safari.