[javascript] jQuery looping .each() JSON key/value not working

I am having problems in looping the key/value of JSON by jQuery .each() function

Initially I have a JSON like this:

json = {"aaa":[
              {"id":"1","data":"aaa1data"}
              ,{"id":"2","data":"aaa2data"}
              ],
        "bbb":[
              {"id":"3","data":"bbb1data"}
              ]
       }

And I would like to loop through all the key/value elements inside the JSON (aaa and bbb) and the retrieve the inner JSON arrays for looping again, so I tried

$(json).each(function(index,data)
{
    var zzz = data;
    $(zzz).each(function(index,data))
    {
       //some other stuff
    }
}

However, I discovered that the first .each() function will regard the whole json as a single structure and will not loop on its element's key.The data parameter received from the .each() function is always the original json itself. I can never get the reference that pointing to the inner JSON array of aaa and bbb.

What would be the problem here and how should I loop for all the key/value elements in a JSON by jQuery properly?

With a simple JSON object, you don't need jQuery:

for (var i in json) {
   for (var j in json[i]) {
     console.log(json[i][j]);
   }
}