Below I have tested the native JSON features. The code below is also run immediately as you load the page, so you will see the actual results as well. Below each test is the web browsers it works in, and the minimum version of it required.
var JSONString = '{"name" : "Robert", "lastName" : "Nyman"}', JSONObject = JSON.parse(JSONString);
Result: FAILED
var obj = { name : "Robert", lastName : "Nyman" }, JSONString = JSON.stringify(obj);
Result: FAILED