Parsing Json Array javascript

I have a problem with a json array.

I have created a jquery ajax function

    $.ajax({
        type: 'POST',
        url: $url,
        data: {id:postData},
        dataType: "json",
        success: function(data) {
            console.log(JSON.stringify(data.productionIndexParent, null, 4));
            console.log(JSON.stringify(data.parentPlants, null, 4));
            console.log(JSON.stringify(data.productionIndex, null, 4));
        },
        error: function(x, t, m) {
            if(t==="timeout") {
                alert("got timeout");
            } else {
                alert(t);
            }
        }
    });

On my codeigniter I print an array data.

echo json_encode($data);

The console.log result is:

{
"12": [
    {
        "id": "25284",
        "PLANTS_id": "12",
        "INDEX_LIST_id": "1",
    },
    {
        "id": "26048",
        "PLANTS_id": "12",
        "INDEX_LIST_id": "2",
    },
    {
        "id": "26812",
        "PLANTS_id": "12",
        "INDEX_LIST_id": "3",
    }
]

}

[
{
    "id": "12",
    "idParent": null,
    "PLANTS_id": "12",
    "SERVICE_STATE_id": "3",
    "last_update_time": "2014-01-27 00:00:00"
}

]

{
"13": [
    {
        "id": "27576",
        "PLANTS_id": "13",
        "INDEX_LIST_id": "1",
    },
    {
        "id": "28340",
        "PLANTS_id": "13",
        "INDEX_LIST_id": "2",
    },
    {
        "id": "29104",
        "PLANTS_id": "13",
        "INDEX_LIST_id": "3",
    }
],
"14": [
    {
        "id": "29868",
        "PLANTS_id": "14",
        "INDEX_LIST_id": "1",
    },
    {
        "id": "30632",
        "PLANTS_id": "14",
        "INDEX_LIST_id": "2",
    },
    {
        "id": "31396",
        "PLANTS_id": "14",
        "INDEX_LIST_id": "3",
    }
]

}

now how i can parse the object array? I have many problems and I don't know how I can parse this array. Thanks F