Manipulate nested object in JS

Question

From this array:

  objNeeded = [
    {onelevel: 'first'},
    {
      onelevel: 'second',
      sublevels: [
        {onelevel: 'domain'},
        {onelevel: 'subdomain'}
      ]
    },
    {
      onelevel: 'third',
      sublevels: [
        {
          onelevel: 'fourth',
          sublevels: [
            {onelevel: 'domain'}
          ]
        }
      ]
    }
  ];

I need to obtain this object:

  objNeeded = {
    first: true,
    second: {
      domain: true,
      subdomain: true
    },
    third: {
      fourth: {
        domain: true
      }
    }
  };

It can be have more nested objects and more objects on the array.

How i can obtain this with JavaScript or Typescript?

@Nicolas I have tried with map, but map return an array and i want an object. — Alessandro_Russo
– Alessandro_Russo, Commented May 12, 2020 at 11:28
You might want to add that in anyways. It might help us helps you. — Nicolas
– Nicolas, Commented May 12, 2020 at 11:34

Nicolas · Accepted Answer · 2020-05-12 11:46:55Z

You could use recursion for that. Since this is a very specific problem to your usecase, i won't bother explain it here. I've left some comment in the code though.

const objNeeded = [
    {onelevel: 'first'},
    {
      onelevel: 'second',
      sublevels: [
        {onelevel: 'domain'},
        {onelevel: 'subdomain'}
      ]
    },
    {
      onelevel: 'third',
      sublevels: [
        {
          onelevel: 'fourth',
          sublevels: [
            {onelevel: 'domain'}
          ]
        }
      ]
    }
  ];
  
  // from what i understand, the rule ares 
  // 1. if the value is a string, it becomes {[key]: true}
  // 2. if there is subLevels, we recursive build the subs arrays. 
 function recursivalySetSubLevels(elements) {
   // this is the output
   const output = {}
   // we parse every element of the array ( or sub array ) and assign them to the current oneLevels value.
   elements.forEach(element => {
    // if the element has subLevels,
    if(!!element.sublevels) {
      // we recursively build the sub object
      output[element.onelevel] = recursivalySetSubLevels(element.sublevels);
    } else {
      // otherwise, we set the key of the oneLevel to true;
      output[element.onelevel] = true;
    }
   });
   // and then return the object.
   return output;
 }
 
 console.log(recursivalySetSubLevels(objNeeded));

prasanth · Accepted Answer · 2020-05-12 11:43:55Z

1

You could do with Array#reduce and recursive call

For Array#reduce use to recreate the array to object format
For recursive call used to find the inner sublevels

const objNeeded = [{onelevel: 'first'}, { onelevel: 'second', sublevels: [ {onelevel: 'domain'}, {onelevel: 'subdomain'} ] }, { onelevel: 'third', sublevels: [ { onelevel: 'fourth', sublevels: [ {onelevel: 'domain'} ] } ] } ];

const res = objNeeded.reduce((acc, {
  onelevel,
  sublevels
}) => (acc[onelevel] = sublevels ? recCall(sublevels) : true, acc), {});

function recCall(arr) {
  return Object.assign({}, ...arr.map(({
    onelevel,
    sublevels
  }) => ({
    [onelevel]: sublevels ? recCall(sublevels) : true
  })))
}

console.log(res)

edited May 12, 2020 at 11:43

answered May 12, 2020 at 11:38

prasanth

22.6k4 gold badges33 silver badges57 bronze badges

Comments

Karan · Accepted Answer · 2020-05-12 12:00:39Z

Here is a function convertObject which can get your desired result.

for (obj of currentObj) will loop through array values and convert the object.

Object.keys(obj) will return array of all the key in the object. and .includes will check whether value passed in parameter is exists in array or not.

Inside convertObject there is a recursion call is there which will be called when current array object has sublevels.

function convertObject(currentObj) {
  // result object
  let result = {};

  // loop through array values
  for (obj of currentObj) {
    // check whethere obj has sublevels or not. If it has sublevels then call recursively.
    if (Object.keys(obj).includes("sublevels")) {
      // retrieve converted object for current object.
      result[obj.onelevel] = convertObject(obj.sublevels, result[obj.onelevel]);
    } else {
      result[obj.onelevel] = true;
    }
  }

  // return result.
  return result;
}

let objNeeded = [{onelevel: 'first'}, { onelevel: 'second', sublevels: [ {onelevel: 'domain'}, {onelevel: 'subdomain'} ] }, { onelevel: 'third', sublevels: [ { onelevel: 'fourth', sublevels: [ {onelevel: 'domain'} ] } ] } ];

console.log(convertObject(objNeeded));

oozywaters · Accepted Answer · 2020-05-12 12:03:17Z

1

Here is another solution:

const objectNeeded = [...];

const reducer = (acc, level) => {
  if (level.onelevel) {
    acc[level.onelevel] = level.sublevels && level.sublevels.length
      ? level.sublevels.reduce(reducer, {})
      : true;
  }
  return acc;
};

// Obtain needed object
objectNeeded = objNeeded.reduce(reducer, {});

edited May 12, 2020 at 12:03

answered May 12, 2020 at 11:52

oozywaters

1,2511 gold badge9 silver badges17 bronze badges

Collectives™ on Stack Overflow

Manipulate nested object in JS

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related