Do NOT have trailing commas in your OBJECT (JSON is a string notation)

UPDATE: you need to use array.splice and not delete if you want to remove items from the array in the object. Alternatively filter the array for undefined after removing

var data = {
  "result": [{
    "FirstName": "Test1",
    "LastName": "User"
  }, {
    "FirstName": "user",
    "LastName": "user"
  }]
}
console.log(data.result);
console.log("------------ deleting -------------");
delete data.result[1];
console.log(data.result); // note the "undefined" in the array.


data = {
  "result": [{
    "FirstName": "Test1",
    "LastName": "User"
  }, {
    "FirstName": "user",
    "LastName": "user"
  }]
}

console.log(data.result);
console.log("------------ slicing -------------");
var deletedItem = data.result.splice(1,1);
console.log(data.result); // here no problem with undefined.

JSfiddle

function deleteEmpty(obj){
        for(var k in obj)
         if(k == "children"){
             if(obj[k]){
                     deleteEmpty(obj[k]);
             }else{
                   delete obj.children;
              } 
         }
    }

for(var i=0; i< a.children.length; i++){
 deleteEmpty(a.children[i])
}

Use array Map method to iterate the careerLevelGroups array and then delete the careerLevels property of an object :

var jsonObj = {
	"careerLevelGroups": [{
			"201801": 58,
			"201802": 74,
			"careerLevel": "Analyst",
			"careerLevels": [{
					"201801": 29,
					"201802": 37,
					"careerID": "10000100"
				},
				{

					"201801": 29,
					"201802": 37,
					"careerID": "10000110"
				}
			]
		},
		{

			"201801": 58,
			"201802": 74,
			"careerLevel": "Consultant",
			"careerLevels": [{

					"201801": 29,
					"201802": 37,
					"careerID": "10000080"
				},
				{

					"201801": 29,
					"201802": 37,
					"careerID": "10000090"
				}
			]
		}
	]
};

var res = jsonObj.careerLevelGroups.map(obj => {
delete obj.careerLevels
return obj;
});

console.log(res);

I always use this very often when filtering an object or an array of objects.

I usually have these in my helpers.ts file. They also make sure that the keys you are filtering does exist in the object and it also has autocomplete.

export function except<T, K extends keyof T>(data: T, keys: Array<K>) {
    const copy = { ...data };
    for (const key of keys) {
        if (key in copy) {
            delete copy[key];
        }
    }
    return copy;
}

export function exceptMany<T, K extends keyof T>(data: Array<T>, keys: Array<K>) {
    return [...data].map((item) => except(item, keys));
}

Then to filter an array of objects, we do:

const data = [
  {
    "addr_id": "41d86d46-8b19-4f4e-be03-f9915ef4947b",
    "addr_type": "postal",
    "addr_linkid_usr": "user1",
    "addr_created": "2021-03-10",
    "addr_updated": "",
    "addr_active": true,
    "addr_postal_as_residential": false,
    "addr_international": false,
    "addr_autocomplete_id": null
  },
  {
    "addr_id": "b18c2ca6-29cf-4114-9067-b37fd3394638",
    "addr_type": "residential",
    "addr_linkid_usr": "user1",
    "addr_created": "2021-03-10",
    "addr_updated": "",
    "addr_active": true,
    "addr_postal_as_residential": true,
    "addr_international": true,
    "addr_autocomplete_id": "string"
  }
];

const results = exceptMany(data, ['addr_linkid_usr', 'addr_created', 'addr_updated']);

Filtering keys from just one object is also possible:

const single = {
    "addr_id": "41d86d46-8b19-4f4e-be03-f9915ef4947b",
    "addr_type": "postal",
    "addr_linkid_usr": "user1",
    "addr_created": "2021-03-10",
    "addr_updated": "",
    "addr_active": true,
    "addr_postal_as_residential": false,
    "addr_international": false,
    "addr_autocomplete_id": null
};

const filteredSingle = except(single, ['addr_linkid_usr', 'addr_created', 'addr_updated']);

Do NOT have trailing commas in your OBJECT (JSON is a string notation)

UPDATE: you need to use array.splice and not delete if you want to remove items from the array in the object. Alternatively filter the array for undefined after removing

var data = {
  "result": [{
    "FirstName": "Test1",
    "LastName": "User"
  }, {
    "FirstName": "user",
    "LastName": "user"
  }]
}
console.log(data.result);
console.log("------------ deleting -------------");
delete data.result[1];
console.log(data.result); // note the "undefined" in the array.


data = {
  "result": [{
    "FirstName": "Test1",
    "LastName": "User"
  }, {
    "FirstName": "user",
    "LastName": "user"
  }]
}

console.log(data.result);
console.log("------------ slicing -------------");
var deletedItem = data.result.splice(1,1);
console.log(data.result); // here no problem with undefined.