[bicknergseng]

IE5 had XHR, but didn't have native JSON support and a number of other features. I think it was on ECMA 1 or 2 until IE5.5, which had 3.

I wager no one uses JSON shims anymore. I don't really know what would happen when you try to use JSON in ECMA 1 or 2.

[yuhong]

Native JSON support was only added in IE8.

[robin_reala]

Anyone that uses jQuery’s (<=1.9) JSON functionality is using a JSON shim:

https://github.com/jquery/jquery/blob/1.9-stable/src/core.js...