How to merge array object value to array if have a same id

Question

I want to merge value to array if it have a same id. I have one array of objects like this.

[ 
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Rosie',
 },
 { 
   id: 'Jane',
   type: 'human',
   favorite: null,
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Lisa',
 },
 { 
   id: 'Steve',
   type: 'hero',
   favorite: 'Jennie',
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Jisoo',
 },
]

and I want to merge key favorite from string to array. I want output like this

[ 
 { 
   id: 'Tony',
   type: 'hero',
   favorite: ['Rosie', 'Lisa', 'Jisoo'],
 },
 { 
   id: 'Jane',
   type: 'human',
   favorite: null,
 },
 { 
   id: 'Steve',
   type: 'hero',
   favorite: ['Jennie'],
 }

and i try to write code like this: (from: Sum similar keys in an array of objects )

var obj = [
    {
      id: 'Tony',
      type: 'hero',
      favorite: 'Rosie',
    },
    {
      id: 'Jane',
      type: 'human',
      favorite: null,
    },
    {
      id: 'Tony',
      type: 'hero',
      favorite: 'Lisa',
    },
    {
      id: 'Steve',
      type: 'hero',
      favorite: 'Jennie',
    },
    {
      id: 'Tony',
      type: 'hero',
      favorite: 'Jisoo',
    },
  ];

  var holder = {};
  const ar = []
  obj.forEach(function (d) {
    if (holder.hasOwnProperty(d.id)) {
      holder[d.id] = ar.push(holder[d.id] + d.favorite);
    } else {
      holder[d.id] = d.favorite;
    }
  });

  var obj2 = [];

  for (var prop in holder) {
    obj2.push({ name: prop, favorite: holder[prop] });
  }

  console.log(obj2);

but out put is

[ { name: 'Tony', favorite: 2 },
  { name: 'Jane', favorite: null },
  { name: 'Steve', favorite: 'Jennie' } ]

How can i do this ?

What have you done so far? Isnt jane's favorite should be [null]? — Eddie
– Eddie, Commented May 16, 2019 at 4:00
i try to write code from stackoverflow.com/questions/24444738/…, and Jane dont have a favourite — Earn Asdsa
– Earn Asdsa, Commented May 16, 2019 at 4:05

Akrion · Accepted Answer · 2019-05-18 21:33:57Z

You can do this with a single Array.reduce and would most likely be the most simple and performant approach:

var data = [ { id: 'Tony', type: 'hero', favorite: 'Rosie', }, { id: 'Jane', type: 'human', favorite: null, }, { id: 'Tony', type: 'hero', favorite: 'Lisa', }, { id: 'Steve', type: 'hero', favorite: 'Jennie', }, { id: 'Tony', type: 'hero', favorite: 'Jisoo', }, ]

let result = data.reduce((r, {id,type,favorite}) => {
  r[id] = r[id] || {id, type, favorite: []}
  r[id].favorite.push(favorite)
  return r
}, {})

console.log(Object.values(result))

The idea is to "group by" the id and then keep pushing to the favorites array on each iteration.

For ES5 you can do it in similar fashion:

var data = [ { id: 'Tony', type: 'hero', favorite: 'Rosie', }, { id: 'Jane', type: 'human', favorite: null, }, { id: 'Tony', type: 'hero', favorite: 'Lisa', }, { id: 'Steve', type: 'hero', favorite: 'Jennie', }, { id: 'Tony', type: 'hero', favorite: 'Jisoo', }, ]

let result = data.reduce(function(r, c){
   r[c.id] = r[c.id] || {id: c.id, type: c.type, favorite: []}
   r[c.id].favorite.push(c.favorite)
   return r
}, {})

console.log(Object.values(result))

There really is no need for lodash to achieve this.

Ori Drori · Accepted Answer · 2019-05-16 04:05:29Z

Group by the id with _.group(), and then merge each group using _.map() and _.mergeWith(), and collect favorite to an array:

const data = [{"id":"Tony","type":"hero","favorite":"Rosie"},{"id":"Jane","type":"human","favorite":null},{"id":"Tony","type":"hero","favorite":"Lisa"},{"id":"Steve","type":"hero","favorite":"Jennie"},{"id":"Tony","type":"hero","favorite":"Jisoo"}]

const result = _(data)
  .groupBy('id')
  .map(g => _.mergeWith({}, ...g, (o, s, k) => {
    if(k !== 'favorite') return // non favorite key are not collected to an array
    
    if(_.isNil(s)) return o // don't add null or undefined to array
    
    return [].concat(o || [], s) // concat other values to array
  }))
  .value()
  
console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script>

Bibberty · Accepted Answer · 2019-05-16 04:09:16Z

0

Use map and Set to get this result.

First we create a new unique Set using the id field.

We seed a new new array from this and call the map method.

const arr = [ 
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Rosie',
 },
 { 
   id: 'Jane',
   type: 'human',
   favorite: null,
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Lisa',
 },
 { 
   id: 'Steve',
   type: 'hero',
   favorite: 'Jennie',
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Jisoo',
 },
];

const masterArr = [...new Set(arr.map((e) => e.id))].map(a => ({
  id: a,
  type: arr.find(x => x.id === a).type,
  favorites: arr.filter(x => x.id === a).map(y => y.favorite)
}));

console.log(masterArr);

answered May 16, 2019 at 4:09

Bibberty

4,7762 gold badges10 silver badges23 bronze badges

Comments

Harish · Accepted Answer · 2019-05-16 04:10:05Z

0

You can use reduce on the array.

const arr = [ 
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Rosie',
 },
 { 
   id: 'Jane',
   type: 'human',
   favorite: null,
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Lisa',
 },
 { 
   id: 'Steve',
   type: 'hero',
   favorite: 'Jennie',
 },
 { 
   id: 'Tony',
   type: 'hero',
   favorite: 'Jisoo',
 },
]
const out = arr.reduce((result, el)=> {
    const id = result.findIndex(e => e.id ===el.id)

    if(id> -1){
        result[id] = {...result[id], favorite: [...result[id].favorite, el.favorite]}
    } else {result.push({...el, favorite: [el.favorite].filter(x => x) })}
    return result
}, [])
console.log(out)

answered May 16, 2019 at 4:10

Harish

1,9111 gold badge15 silver badges26 bronze badges

Comments

Ali Elkhateeb · Accepted Answer · 2019-05-16 04:21:55Z

0

Just loop over the array and construct a new array after converting favorite attribute into an array, then for next elements with the same id, push to favorite array

let users = [{id: 'Tony', type: 'hero', favorite: 'Rosie',}, {id: 'Jane', type: 'human', favorite: null,}, {id: 'Tony', type: 'hero', favorite: 'Lisa',}, {id: 'Steve', type: 'hero', favorite: 'Jennie',}, {id: 'Tony', type: 'hero', favorite: 'Jisoo',},];

// To combine friends of the same user in an array at property friendNames
let merged = {};
for (let user of users) {
    if (typeof merged[user.id] === 'undefined') {
        user.favorite = [user.favorite];
        merged[user.id] = user;
    } else {
        merged[user.id].favorite.push(user.favorite)
    }
}

console.log(Object.values(merged));

edited May 16, 2019 at 4:21

answered May 16, 2019 at 4:07

Ali Elkhateeb

3,8335 gold badges26 silver badges43 bronze badges

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