CODEWITHSUNDEEP
javascriptecmascript-6
alice_morgan
alice_morgan

Reputation: 171

transform array of object to object of array?

I want to change this

const a = [{
        id: 1,
        name: 'a'
      }, {
        id: 2,
        name: 'b'
      }]

to

{
        id: [1,2],
        name: [a, b]
      }

I'm stuck at how to push the id and name into the object

 arr.reduce((accum, val) => {
    let accum = {
      id: val.id,
      name: val.name
    }
    accum.id.push(val.id) //it doesn't work like this
    return accum
  }, {})

Upvotes: 0

Views: 63

Answers (3)

Mr. Polywhirl
Mr. Polywhirl

Reputation: 48600

If you want to build a list of values for each key, you could reduce every item; and for each item, reduce their key-value pairs.

In the example below, the keyValues function is decoupled from the sample data.

const keyValues = (...items) =>
  items.reduce((accOut, item) =>
    Object.entries(item).reduce((accIn, [key, value]) =>
      ({ ...accIn, [key]: [...(accIn[key] || []), value] }), accOut), {})

const data = [
  { id: 1, name: 'a' },
  { id: 2, name: 'b' }
];

console.log(keyValues(...data));
.as-console-wrapper { top: 0; max-height: 100% !important; }

Alternatively, you could zip the data and then bin it.

const zip = (...arr) => arr[0].map((_, c) => arr.map(row => row[c]))

const bin = (...arr) =>
  zip(...arr.map(Object.entries)).reduce((acc, ...values) =>
    ({ ...acc, [values[0][0][0]]: values[0].map(([key, value]) => value) }), {})

const data = [
  { id: 1, name: 'a' },
  { id: 2, name: 'b' }
];

console.log(bin(...data));
.as-console-wrapper { top: 0; max-height: 100% !important; }

Upvotes: 0

Kinglish
Kinglish

Reputation: 23654

You were just missing the proper initial accum value, which would contain the arrays you want.

const a = [{
  id: 1,
  name: 'a'
}, {
  id: 2,
  name: 'b'
}]


let arr = a.reduce((accum, val) => {
  accum.id.push(val.id);
  accum.name.push(val.name);
  return accum
}, {
  id: [],
  name: []
})
console.log(arr)

Upvotes: 1

Harcop Toluwap
Harcop Toluwap

Reputation: 61

const a = [{
        id: 1,
        name: 'a'
      }, {
        id: 2,
        name: 'b'
      }]
 const newObj = {};
 
a.forEach(ele => {
  const {id, name} = ele;
  newObj.id.push(id);
  newObj.name.push(name);
})

console.log(newObj);

Upvotes: 0

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