CODEWITHSUNDEEP
javascriptjsonrecursiontraversal
Leandro Ferreira Fernandes
Leandro Ferreira Fernandes

Reputation: 291

Javascript - Couting all nested objects of JSON

Suppose I have the following JSON:

{
  "id": "foo",
  "list": [
    {
      "id": "A",
      "list": [
        {
          "id": "B",
          "list": [
            {
              "id": "C",
              "list": [
                {
                  "id": "D",
                  "list": []
                },
                {
                  "id": "E",
                  "list": []
                }
              ]
            },
            {
              "id": "F",
              "list": []
            },
            {
              "id": "G",
              "list": [
                {
                  "id": "H",
                  "list": []
                },
                {
                  "id": "I",
                  "list": []
                },
                {
                  "id": "J",
                  "list": []
                }
              ]
            }
          ]
        },
        {
          "id": "K",
          "list": []
        }
      ]
    },
    {
      "id": "L",
      "list": [
        {
          "id": "M",
          "list": []
        }
      ]
    },
    {
      "id": "N",
      "list": []
    },
    {
      "id": "O",
      "list": [
        {
          "id": "P",
          "list": [
            {
              "id": "Q",
              "list": []
            },
            {
              "id": "R",
              "list": []
            },
            {
              "id": "S",
              "list": []
            },
            {
              "id": "T",
              "list": [
                {
                  "id": "U",
                  "list": []
                }
              ]
            },
            {
              "id": "V",
              "list": [
                {
                  "id": "W",
                  "list": [
                    {
                      "id": "X",
                      "list": []
                    },
                    {
                      "id": "Y",
                      "list": []
                    },
                    {
                      "id": "Z",
                      "list": []
                    }
                  ]
                }
              ]
            }
          ]
        }
      ]
    }
  ]
}

My question is: How could I count each of the childs and append this number into a property of each object?

Example:

Regarding this, the "C" object should have a property, let's name it "allBelow", containing the number 2. The "W" object containing 3, and the "V" object containing 4. And so on, for each object.

I wonder that some recursive function could do this job but I'm not achieving it.

Could you please help me?

Bests,

Upvotes: 1

Views: 759

Answers (4)

ibrahim mahrir
ibrahim mahrir

Reputation: 31692

var myObj = {"id":"foo","list":[{"id":"A","list":[{"id":"B","list":[{"id":"C","list":[{"id":"D","list":[]},{"id":"E","list":[]}]},{"id":"F","list":[]},{"id":"G","list":[{"id":"H","list":[]},{"id":"I","list":[]},{"id":"J","list":[]}]}]},{"id":"K","list":[]}]},{"id":"L","list":[{"id":"M","list":[]}]},{"id":"N","list":[]},{"id":"O","list":[{"id":"P","list":[{"id":"Q","list":[]},{"id":"R","list":[]},{"id":"S","list":[]},{"id":"T","list":[{"id":"U","list":[]}]},{"id":"V","list":[{"id":"W","list":[{"id":"X","list":[]},{"id":"Y","list":[]},{"id":"Z","list":[]}]}]}]}]}]};

function count(obj) {
  var c = obj.list.length;
  c += obj.list.reduce((a, e) => a + count(e), 0);
  obj.count = c; // assign the count after counting the subobjects.
  return c; // return the count to be used by parent objects
}

count(myObj);

console.log(myObj);

Upvotes: 2

fafl
fafl

Reputation: 7385

A recursive function is a good idea. Try this:

var data = {"id":"foo","list":[{"id":"A","list":[{"id":"B","list":[{"id":"C","list":[{"id":"D","list":[]},{"id":"E","list":[]}]},{"id":"F","list":[]},{"id":"G","list":[{"id":"H","list":[]},{"id":"I","list":[]},{"id":"J","list":[]}]}]},{"id":"K","list":[]}]},{"id":"L","list":[{"id":"M","list":[]}]},{"id":"N","list":[]},{"id":"O","list":[{"id":"P","list":[{"id":"Q","list":[]},{"id":"R","list":[]},{"id":"S","list":[]},{"id":"T","list":[{"id":"U","list":[]}]},{"id":"V","list":[{"id":"W","list":[{"id":"X","list":[]},{"id":"Y","list":[]},{"id":"Z","list":[]}]}]}]}]}]};

function addCount(node) {
  node.count = 0;
  for (var i = 0; i < node.list.length; i++) {
    var child = node.list[i];
    addCount(child);
    node.count += child.count + 1;
  }
}

addCount(data);
console.log(data)

It first calls itself on each child node. Then it adds each child to the count as 1 + the number of grandchildren (or grand-grand- or more).

Upvotes: 0

Th0rndike
Th0rndike

Reputation: 3436

A depth first search should work, I'm thinking something like this (UNTESTED CODE): 

function DFS(tree){
    var currentCount = tree.list.length;
    for(var i=0;i<count;i++){
        currentCount += DFS(tree.list[i]);
    }
    tree["count"] = currentCount;
    return currentCount;
}

Upvotes: 0

Vic
Vic

Reputation: 8981

You can do a simple DFS:

function appendNumChildren(currentNode) {  
  const totalChildren = currentNode.list.reduce((acc, node) => {
    return acc + appendNumChildren(node);
  }, 0)

  currentNode.allBelow = totalChildren;

  return totalChildren + 1;
}

appendNumChildren(json);

https://jsbin.com/qekabatuwi/edit?js,console

Upvotes: 2

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