How to get an ad id in Android or iOS IDFA through a mobile site?

Question

I have been looking for this for a while and cannot find a definitive answer.

AAID or IDFA is the key to publisher monetization. Without this, publishers should return to the old-fashion cookie match, which is ineffective (in terms of latency and bandwidth usage) and inefficient (in terms of data set, as mobile user behavior is mainly related to AAID / IDFA, cookies instead)

You can expect that the default browser in Android / iOS (Chrome / Safari) should provide some Javascript interface for web pages to get this important (for the publisher) and insensitive (for the user) identifier. However, I could not find such a thing. Perhaps they are pushing developers to develop mobile mobile applications.

So, is there a way to get AAID / IDFA on web pages? Or is there another way I can associate a visitor with an AAID / IDFA?