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

user_6662421 0
Viewed 71

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);

typescript ecmascript-6 javascript
4 Answers

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;
}, []));

user_47824230

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);

user_96952860

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);

user_62389770

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.

user_57784620
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