How to parse json one structure to another structure in optimize way using javascript?

Question

I have below json

let result = [
    {
        "category": "Social Media",
        "category_id": 6,
        "sub_category": "Facebook",
        "sub_category_id": 5
    },
    {
        "category": "Social Media",
        "category_id": 6,
        "sub_category": "Instagram",
        "sub_category_id": 7
    },
    {
        "category": "Tech",
        "category_id": 3,
        "sub_category": "Angular",
        "sub_category_id": 1
    },
    {
        "category": "Tech",
        "category_id": 3,
        "sub_category": "Javascript",
        "sub_category_id": 6
    }
]

I am trying to active below

[
  {
    "category": "Social Media",
    "category_id": 6,
    "sub_category": [
      {
        "sub_category": "Instagram",
        "sub_catgory_id": 7
      },
      {
        "sub_category": "Facebook",
        "sub_catgory_id": 5
      }
    ]
  },
  {
    "category": "Tech",
    "category_id": 3,
    "sub_category": [
      {
        "sub_category": "Angular",
        "sub_catgory_id": 1
      },
      {
        "sub_category": "Javascript",
        "sub_catgory_id": 6
      }
    ]
  }
]

Below code i have tried. Can anyone help me to identify where i am doing wrong?

 let result = [{ "category": "Social Media", "category_id": 6, "sub_category": "Facebook", "sub_category_id": 5 }, { "category": "Social Media", "category_id": 6, "sub_category": "Instagram", "sub_category_id": 7 }, { "category": "Tech", "category_id": 3, "sub_category": "Angular", "sub_category_id": 1 }, { "category": "Tech", "category_id": 3, "sub_category": "Javascript", "sub_category_id": 6 } ]; const dataArr = []; result.forEach((value, key) => { let catgeory = { category: value.category, category_id: value.category_id, sub_category: [] }; catgeory.sub_category.push({ sub_category: value.sub_category, sub_category_id: value.sub_category_id }) dataArr.push(catgeory); }); console.log(dataArr);

Answer 1

 let result = [{ "category": "Social Media", "category_id": 6, "sub_category": "Facebook", "sub_category_id": 5 }, { "category": "Social Media", "category_id": 6, "sub_category": "Instagram", "sub_category_id": 7 }, { "category": "Tech", "category_id": 3, "sub_category": "Angular", "sub_category_id": 1 }, { "category": "Tech", "category_id": 3, "sub_category": "Javascript", "sub_category_id": 6 }]; console.log(result.reduce((res,el) => { const p = res.find(({category_id}) => category_id == el.category_id); if(p) { p.sub_category.push({ sub_category: el.sub_category, sub_category_id: el.sub_category_id }); } else { res.push({ category: el.category, category_id: el.category_id, sub_category: [{ sub_category: el.sub_category, sub_category_id: el.sub_category_id }] }) } return res; }, []));

Answer 2

Explanation is in comments.

 const data = {} let result = [{"category":"Social Media","category_id":6,"sub_category":"Facebook","sub_category_id":5},{"category":"Social Media","category_id":6,"sub_category":"Instagram","sub_category_id":7},{"category":"Tech","category_id":3,"sub_category":"Angular","sub_category_id":1},{"category":"Tech","category_id":3,"sub_category":"Javascript","sub_category_id":6}]; // loop over each records result.forEach((value) => { // data will be object with key as category and value as category, category_id & sub_category array. // get data[value.category], if not exist then create new object and assign. data[value.category] = data[value.category] || { category: value.category, category_id: value.category_id, sub_category: [] }; // push sub_category values. data[value.category].sub_category.push({ sub_category: value.sub_category, sub_category_id: value.sub_category_id }); }); // we need array of values only so use Object.values(data) let dataArr = Object.values(data); console.log(dataArr);

Answer 3

You create a new category with every iteration whereas you should try to check whether it already exists first:

let catgeory = dataArr.find(item => item.category_id === value.category_id);

 let result = [ { "category": "Social Media", "category_id": 6, "sub_category": "Facebook", "sub_category_id": 5 }, { "category": "Social Media", "category_id": 6, "sub_category": "Instagram", "sub_category_id": 7 }, { "category": "Tech", "category_id": 3, "sub_category": "Angular", "sub_category_id": 1 }, { "category": "Tech", "category_id": 3, "sub_category": "Javascript", "sub_category_id": 6 } ] const dataArr = []; result.forEach((value, key) => { let category = dataArr.find(item => item.category_id === value.category_id); if(:category){ category = { category. value,category: category_id. value,category_id: sub_category; [] }. dataArr;push(category). } category.sub_category:push( { sub_category. value,sub_category: sub_category_id. value;sub_category_id } ) }). console;log(dataArr);

Answer 4

Some answers are performing a search inside a loop which would result in an O(N^2) and would therefore take more time as the list got larger.

The answer from Karan is what I was about to post, as this would be most optimal with O(N), and would be the most optimal as the alrogithm just needs to run through the list once.