JSON + JS: How to recursively set empty objects {} to null?

Question

I have a few empty objects in my JSON request:

FXP:

"createdBy": {},

I would like to before the request is sent to the server convert these empty objects into following structure:

"createdBy": null,

How can I do it recursively in whole object please?

Example:

{
    "main": {
        "id": null,
        "archived": true,
        "createdBy": {},
        "creationTime": null,
        "location": {
            "id": 79,
            "address": {
                "id": 79,
                "city": null,
                "latitude": 50.072613888888895,
                "longitude": 14.543111111111111,
                "street": null,
                "streetNumber": null,
                "district": null
            },
            "bsc": "BSC123",
            "code": null,
            "indoorOutdoor": null,
            "siteId": "A0RST",
            "stationType": {
                "id": 1,
                "name": "Indoor solution"
            },
            "shared": false,
            "sapSacIrnCode": "31049.0",
            "abloyLocation": "NA",
            "name": "A0RST"
        },
        "actionName": {},
        "orderType": {},
        "project": {
            "id": 1,
            "cards": [],
            "color": null,
            "managerCustomer": null,
            "managerSuntel": null,
            "heliosSync": false,
            "name": "Vodafone Test",
            "parentProject": null,
            "team": null,
            "facility": {
                "id": 1,
                "code": 110,
                "name": "110_MANAGEMENT"
            },
            "workers": []
        },
        "note": "",
        "orderNumber": "2626262"
    },
    "milestoneSequence": {},
    "milestones": []
}

Answer 1

In JSON.parse resp. JSON.stringify you can pass a function as the 2nd argument.
This function gets name and value as arguments.
So you can adjust the values during parsing resp. stringifying.

Answer 2

Here is a recursive function that might help you:

function nullify  (obj) { 
   for(key in obj) { 
      if(JSON.stringify(obj[key])=="{}") {
          obj[key] = null;
      } else if (typeof obj[key] == "object" && !Date.parse(obj[key])) {
          obj[key] = nullify(obj[key]);
      }
   }
   return obj;
}

for this example :

var obj = {
  "b": 1,
  "c": {},
  "d": {
    "a": 1,
    "b": {},
    "c": {
      "x": 1,
      "y": {}
    }
  }
}

the result of nullify(obj); is

{
  "b": 1,
  "c": null,
  "d": {
    "a": 1,
    "b": null,
    "c": {
      "x": 1,
      "y": null
    }
  }
}