Perhaps:
{
"folders": [
{ "id":123, "private":0, "archived":0, "order":1, "title":"Shopping" },
...
]
}
Because there is not an exact correspondence between XML and JSON, you are free (e.g. have to define) how the two data-structures map. For instance, in the above, the “folder” element is implicit in the nested objects in the “folders” array.
This could be expanded as in:
"folders": [{"folder": { .... }]
Etc, but there is still the problem of not being able to capture content+attributes as consistently as XML. In any case, your data-structure -> JSON|XML serializer likely works in a particular way (and please, please, use a library, not “hand-rolled” JSON-string-munging). That is; the format of the XML and JSON should be uniformly dictated (somehow) by the data-structure for transmission.