Key array of objects by object key nested in another object inside another array?

Question

I have this data structure and want to change it using lodash using keyBy

[
  {
    names: [
      {
        id: 1,
        name: 'aa',
      },
      {
        id: 2,
        name: 'bb',
      },
    ],
    date: '2020-11-02',
  },
  {
    names: [
      {
        id: 3,
        name: 'cc',
      },
    ],
    date: '2020-11-10',
  },
]

And would like to use lodash to to change it so it's just an object of objects where every single name is an object with the id as a reference. Don't really care if the date is removed or not don't need it. It should look something like this.

  1: {
    id: 1,
    name: 'aa',
  },
  2: {
    id: 2,
    name: 'bb',
  },
  3:{
    id: 3,
    name: 'cc',
  }

Tried doing this but it just returns an empty object

_.chain(array)
      .keyBy('id')
      .mapValues(function (item) {
        item.name= _.keyBy(item.name, 'id')
        return item
      })
      .value()

It would be really helpful if you added the desired output to your question. — devserkan
– devserkan, Commented Nov 11, 2020 at 21:03

dave · Accepted Answer · 2020-11-11 21:17:01Z

2

This isn't using lodash, but this is as simple as:

.flatMap(i => i.names)
.reduce((c, i) => {
    c[i.id] = i;
    return c;
}, {})

console.log([
  {
    names: [
      {
        id: 1,
        name: 'aa',
      },
      {
        id: 2,
        name: 'bb',
      },
    ],
    date: '2020-11-02',
  },
  {
    names: [
      {
        id: 3,
        name: 'cc',
      },
    ],
    date: '2020-11-10',
  },
].flatMap(i => i.names)
    .reduce((c, i) => {
        c[i.id] = i;
        return c;
    }, {}))

answered Nov 11, 2020 at 21:17

dave

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3 Comments

devserkan Over a year ago

I was going to provide an answer with a double reduce but flatMap rocks. I should remember it more frequently.

meowzart Over a year ago

Oh really nice solution. Yeah flatMap is really nice :)

meowzart Over a year ago

If you want to show your solution using double reduce I would still like to take a look at it :) Always nice to know more then one solution and reduce confuses the hell out of me!

Ori Drori · Accepted Answer · 2020-11-11 22:22:41Z

1

With lodash you can use _.flatMap() to convert the names to a single array, and then use _.keyBy() to convert to an object:

const arr = [{"names":[{"id":1,"name":"aa"},{"id":2,"name":"bb"}],"date":"2020-11-02"},{"names":[{"id":3,"name":"cc"}],"date":"2020-11-10"}]

const result = _.keyBy(
  _.flatMap(arr, 'names'),
  'id'
)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.20/lodash.min.js" integrity="sha512-90vH1Z83AJY9DmlWa8WkjkV79yfS2n2Oxhsi2dZbIv0nC4E6m5AbH8Nh156kkM7JePmqD6tcZsfad1ueoaovww==" crossorigin="anonymous"></script>

answered Nov 11, 2020 at 22:22

Ori Drori

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