Best way to flatten JS object (keys and values) to a single depth array

I wanted to flatten my deep object to one level depth. None of the above solutions worked for me.

My input:

{
    "user": {
        "key_value_map": {
            "CreatedDate": "123424",
            "Department": {
                "Name": "XYZ"
            }
        }
    }
}

Expected output:

{
    "user.key_value_map.CreatedDate": "123424",
    "user.key_value_map.Department.Name": "XYZ"
}

Code that worked for me:

function flattenObject(ob) {
    var toReturn = {};

    for (var i in ob) {
        if (!ob.hasOwnProperty(i)) continue;

        if ((typeof ob[i]) == 'object' && ob[i] !== null) {
            var flatObject = flattenObject(ob[i]);
            for (var x in flatObject) {
                if (!flatObject.hasOwnProperty(x)) continue;

                toReturn[i + '.' + x] = flatObject[x];
            }
        } else {
            toReturn[i] = ob[i];
        }
    }
    return toReturn;
}