How to check if JavaScript object is JSON

I have a nested JSON object that I need to loop through, and the value of each key could be a String, JSON array or another JSON object. Depending on the type of object, I need to carry out different operations. Is there any way I can check the type of the object to see if it is a String, JSON object or JSON array?

I tried using typeof and instanceof but both didn't seem to work, as typeof will return an object for both JSON object and array, and instanceof gives an error when I do obj instanceof JSON.

To be more specific, after parsing the JSON into a JS object, is there any way I can check if it is a normal string, or an object with keys and values (from a JSON object), or an array (from a JSON array)?

For example:

JSON

var data = "{'hi':
             {'hello':
               ['hi1','hi2']
             },
            'hey':'words'
           }";

Sample JavaScript

var jsonObj = JSON.parse(data);
var path = ["hi","hello"];

function check(jsonObj, path) {
    var parent = jsonObj;
    for (var i = 0; i < path.length-1; i++) {
        var key = path[i];
        if (parent != undefined) {
            parent = parent[key];
        }
    }
    if (parent != undefined) {
        var endLength = path.length - 1;
        var child = parent[path[endLength]];
        //if child is a string, add some text
        //if child is an object, edit the key/value
        //if child is an array, add a new element
        //if child does not exist, add a new key/value
    }
}

How do I carry out the object checking as shown above?