Aggregate string into Array using _.groupBy in lodash

Question

Given:

const data = [
  { user: "user1", data: "data11" },
  { user: "user1", data: "data12" },
  { user: "user1", data: "data13" },
  { user: "user2", data: "data21" },
  { user: "user2", data: "data22" }
];

const output = _(data).groupBy('user')
      .map((vals, key) => ({ 'user': key, 'data': _.take(vals, 'data')}))
      .value();

console.log(output)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

How to get output like this by lodash _.groupBy :

const output = [{user:'user1',data:['data11','data12','data13']},
                {user:'user2',data:['data21','data22']}]

Thanks!

Yeah, he tried heading over to SO and asking some else to do it for him. — gforce301, Jan 21 '20 at 07:38
_(data).groupBy('user') .map((vals, key) => ({ 'user': key, 'data': _.take(vals,'data') })) .value(); — Jerry, Jan 21 '20 at 07:40
@Jerry (I think my previous comment gave the incorrect output) change `_.take` with `._map` in your code and it should work — Nick Parsons, Jan 21 '20 at 07:44
@NickParsons I have reopened. You can post an answer (Or close if you have a better duplicate target) — adiga, Jan 21 '20 at 07:56

Nick Parsons · Accepted Answer · 2020-01-21T08:11:07.283

You've almost got it. Lodash's _.take() method is used to slice the first n items from an array of items. Instead, you want to _.map your array of grouped objects to an array of data strings by "extracting" data attribute from each object. This can be done using _.map(vals, 'data'). See example below:

const data = [
  { user: "user1", data: "data11" },
  { user: "user1", data: "data12" },
  { user: "user1", data: "data13" },
  { user: "user2", data: "data21" },
  { user: "user2", data: "data22" }
];

const output = _(data).groupBy('user')
      .map((vals, user) => ({ user, 'data': _.map(vals, 'data')})).value();

console.log(output)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

Aggregate string into Array using _.groupBy in lodash

1 Answers1