How to filter arrya with keys in object and create new object

Question

How can I filter the rooms array with elements in the object and if it matches to object id in the array of objects with item type "Room" add count key with count to the main array?

The First Array that I get from API

[ 
  {
    rooms: [ 'f03e6e40-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '8c6a6070-80c0-11eb-9753-bb149505e85f',
    itemName: 'Item 1’,
  },
  {
    rooms: [ 'eef60fc0-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '3aede320-870f-11eb-9e58-9d6fb0d8b5a8',
    itemName: 'Item 2'
  },
  {
    rooms: [ 'f03e6e40-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '3ad52b00-870f-11eb-8f84-0782ebd81006',
    itemName: ‘Item3’ 
  },
  { 
    itemType: 'Room',
    id: 'f03e6e40-870d-11eb-88a2-0149a30c02c5',
    itemName: 'Bedroom’
  },
  { 
    itemType: 'Room',
    id: 'eef60fc0-870d-11eb-88a2-0149a30c02c5',
    itemName: 'Bedroom 2' 
  },
 ]

I want to filter the rooms array with elements in the object and if it matches to object id in the array of objects with itemtType "Room" add count key with count to main array as below.

[ 
{
    rooms: [ 'f03e6e40-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '8c6a6070-80c0-11eb-9753-bb149505e85f',
    itemName: 'Item 1’,
},
  {
    rooms: [ 'eef60fc0-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '3aede320-870f-11eb-9e58-9d6fb0d8b5a8',
    itemName: 'Item 2'
 },
  {
    rooms: [ 'f03e6e40-870d-11eb-88a2-0149a30c02c5' ],
    itemType: 'Item',
    id: '3ad52b00-870f-11eb-8f84-0782ebd81006',
    itemName: ‘Item3’ 
},
  { 
    itemType: 'Room',
    id: 'f03e6e40-870d-11eb-88a2-0149a30c02c5',
    itemName: 'Bedroom’,
    count: 2
 },
  { 
    itemType: 'Room',
    id: 'eef60fc0-870d-11eb-88a2-0149a30c02c5',
    itemName: 'Bedroom 2',
    count: 1
},
 ]

Answer 1

You can use Array.prototype.map to transform the input array and add the count property to the elements with an itemType of 'Room' . You can use Array.prototype.filter and Array.prototype.includes to count the number of rooms.

 const arr = [ { rooms: ['f03e6e40-870d-11eb-88a2-0149a30c02c5'], itemType: 'Item', id: '8c6a6070-80c0-11eb-9753-bb149505e85f', itemName: 'Item 1', }, { rooms: ['eef60fc0-870d-11eb-88a2-0149a30c02c5'], itemType: 'Item', id: '3aede320-870f-11eb-9e58-9d6fb0d8b5a8', itemName: 'Item 2', }, { rooms: ['f03e6e40-870d-11eb-88a2-0149a30c02c5'], itemType: 'Item', id: '3ad52b00-870f-11eb-8f84-0782ebd81006', itemName: 'Item3', }, { itemType: 'Room', id: 'f03e6e40-870d-11eb-88a2-0149a30c02c5', itemName: 'Bedroom', }, { itemType: 'Room', id: 'eef60fc0-870d-11eb-88a2-0149a30c02c5', itemName: 'Bedroom 2', }, ] const result = arr.map((element) => { if (element.itemType.== 'Room') { return element } return {..,element: count. arr.filter( (i) => i.itemType === 'Item' && i.rooms.includes(element.id) ),length. } }) console.log(result)