recursively delete all JSON keys with null values and delete parent key if all child keys are deleted

Question

I'm trying to recursively delete null values in a JSON object and all Subobjects. If the subobjects keys are all deleted, then I want that subobject to be deleted as well.

ie.

x = {
  "applicant": {
    'first_name': null,
    'last_name': null,
    'employment_type': null
  },
  'phone': 1123123,
  'branch': null,
  'industry': {
    'id': 1,
    'name': null
  },
  "status": "333"
}

should turn into this:

x = {
    'phone': 1123123,
    'industry': {
         "id": 1
     },
     "status": "333"
    }

Here is the function that I wrote to delete all keys with null values:

function delKeys(app){
  for(key in app){
    if(app[key] !== null && typeof(app[key]) === 'object'){
      delKeys(app[key])
    } 
    if(app[key] === null){
      delete app[key]
      }
  }

But this doesn't delete the parent key with no children:

so instead of the result above, I get this:

x = {
    "applicant":{},
    "phone":1123123,
    "industry":{
       'id': 1
     }
     "status": "333"
     }

As you can see, it doesn't delete the applicant key. How would I check for that within the function? or does it need to be written in a separate function that I call AFTER calling delKeys()?

Also, does anyone see this hitting maximum recursion depth? I've tried with bigger JSON objects and it seems to be hitting max recursion depth. I would really appreciate help with debugging that

thank you.

Answer 1

You need to check if app[key] has keys after you delete null keys.

const x = {
  "applicant": {
    'first_name': null,
    'last_name': null,
    'employment_type': null
  },
  'phone': 1123123,
  'branch': null,
  'industry': {
    'id': 1,
    'name': null
  },
  "status": "333"
}

function isEmpty(obj) {
  for(var key in obj) return false;

  return true
}

function delKeys(app){
  for(var key in app){
    if(app[key] !== null && typeof(app[key]) === 'object'){
      delKeys(app[key])

      if(isEmpty(app[key])) {
        delete app[key]
      }
    } 
    if(app[key] === null){
      delete app[key]
    }
  }
}

delKeys(x)

console.log(x)