How to transform an object into an array of objects by keys?

Question

I have an object of the following type:

const obj =  [
  {
    id:1,
    name:'Admin',
    new: [{text:'text', count:4}],
    old: [],
    ongoing: [{text: 'text1', count:5}]
  }
]

I need to get array with objects if they exist in new, old, ongoing object properties

expected result

[
 {
        "id": 1,
        "level": "new",
        "text": "text" ,
        "count": 4,  
     },
{
        "id": 1,
        "level": "ongoing",
        "text": "text1" ,
        "count": 5,  
     },
]

That is, if arrays of objects are available in the object using the keys new, ongoing, old, I create for each object and add to the array, if the key is empty, then I skip

My solution

let data = []
  
    guidance.map((guidanceEntity) => {

      guidanceEntity?.new?.sort((a, b) => b.count - a.count).slice(0, 1)
                     .map(guidanceItem => {
        data.push(
            {
              id: guidanceEntity.id,
              level: 'new',
              text: guidanceItem.text,
              count: guidanceItem.count,
            },
        )
      })

      guidanceEntity?.ongoing?.sort((a, b) => b.count - a.count).slice(0, 1)
                     .map(guidanceItem => {
        data.push({
          id: guidanceEntity.id,
          level: 'ongoing',
          text: guidanceItem.text,
          count: guidanceItem.count,
        })
      })

      guidanceEntity?.old?.sort((a, b) => b.count - a.count).slice(0, 1)
                     .map(guidanceItem => {
        data.push({
          id: guidanceEntity.id,
          level: 'old',
          text: guidanceItem.text,
          count: guidanceItem.count,
        })
      })
    })

so you only need the first item of each sub-array (wrt sorting)? — georg
– georg, Commented Jun 4, 2021 at 7:45
const obj = [ { ... } ]; it looks like you have an array of objects, not an object; can you confirm, please? — secan
– secan, Commented Jun 4, 2021 at 7:45
guidanceEntity?.new?.sort((a, b) => b.count - a.count).slice(0, 1).map(guidanceItem => { ... } does not make a lot of sense; if you want just the first item, you can simply select it with guidanceEntity?.new?.sort((a, b) => b.count - a.count)[0] then, if you have a single item, it makes non sense to use map (the same goes for ongoing and old) — secan
– secan, Commented Jun 4, 2021 at 7:56

Bera Koç · Accepted Answer · 2021-06-04 07:56:34Z

2

For each object you can apply a transform like below:

const obj = {
  id: 1,
  name: 'Admin',
  new: [{
    text: 'text',
    count: 4
  }],
  old: [],
  ongoing: [{
    text: 'text1',
    count: 5
  }]
}

const targetKeys = ['new', 'old', 'ongoing']

const transform = o => targetKeys.reduce((acc, curr) => acc.concat(o[curr].length ? {
  id: o.id,
  level: curr,
  text: o[curr][0].text,
  count: o[curr][0].count
} : []), [])

console.log(transform(obj))

answered Jun 4, 2021 at 7:56

Bera Koç

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Comments

adiga · Accepted Answer · 2021-06-04 09:32:06Z

1

Go through the new, old and ongoing arrays of each object and get the object with biggest count value. You can do this linearly using reduce instead of sort.

const obj=[{id:1,name:"Admin",new:[{text:"text",count:4}],old:[],ongoing:[{text:"text1",count:5}]}],
    levels = ['new', 'old', 'ongoing'],
    biggest = (arr, key) => arr.reduce((a, b) => a[key] > b[key] ? a : b),
    output = []
    
for (const o of obj) {
  for (const level of levels)
    if (o[level].length)
      output.push({ id: o.id, level, ...biggest(o[level], "count") })
}

console.log(output)

edited Jun 4, 2021 at 9:32

answered Jun 4, 2021 at 8:12

adiga

35.4k9 gold badges65 silver badges88 bronze badges

Comments

secan · Accepted Answer · 2021-06-04 08:24:29Z

If I understood correctly what you want to achieve, this should do:

const objArr = [{
  id: 1,
  name: 'Admin',
  new: [{
    text: 'text',
    count: 4
  }],
  old: [],
  ongoing: [{
    text: 'text1',
    count: 5
  }]
}]

const data = objArr.reduce((output, item) => {
  /* 
   * for each item in the object array,
   * sort the `new`, `ongoing` and `old` attributes,
   * then select the first element for each
   */
  const newItem = (item.new || []).sort((a, b) => b.count - a.count)[0] || null;
  const ongoingItem = (item.ongoing || []).sort((a, b) => b.count - a.count)[0] || null;
  const oldItem = (item.old || []).sort((a, b) => b.count - a.count)[0] || null;
  
  /*
   * if there is at least one element, either `new` `ongoing` or `old`
   * add the attributes `id` and `level` to the element object,
   * then push it into the output array
   */
  if (newItem || ongoingItem || oldItem) {
    newItem && output.push({ id: item.id, level: 'new', ...newItem });
    ongoingItem && output.push({ id: item.id, level: 'ongoing', ...ongoingItem });
    oldItem && output.push({ id: item.id, level: 'old', ...oldItem });
  }
  
  return output
}, []);

console.log(data)

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