How to convert an array of objects in an array of integers extracting values from those objects using ramda.js?

Question

I'm trying to convert an array of objects into an array of integers extracting values from those objects using Ramda.js. I need to keep just the node participants with the uid values, however, it seems that I'm not doing this correctly.

I'm want to transform this

var listObejcts = {
  "participants": [
    {
      "entity": {
        "uid": 1
      }
    },
    {
      "entity": {
        "uid": 2
      }
    }
  ]
}

to this:

{
  "participants": [1, 2]
}

I've tried the code above but it didn't work. It's still returning a list of objects.

var transform = pipe(
  over(lensProp('participants'), pipe(
    filter(pipe(
      over(lensProp('entity'), prop('uid'))
    ))
  ))
)

console.log(transform(listObejcts))

Does anybody know how I could achieve that?

It's possible to edit the code here - https://repl.it/repls/PrimaryMushyBlogs

Scott Sauyet · Accepted Answer · 2019-03-31 19:32:53Z

5

One possibility is to combine evolve with map(path) like this:

const transform = evolve({participants: map(path(['entity', 'uid']))})

var listObjects = {participants: [{entity: {uid: 1}}, {entity: {uid: 2}}]}

console.log(transform(listObjects))

<script src="https://bundle.run/[email protected]"></script><script>
const {evolve, map, path} = ramda  </script>

While I'm sure that there is a lens-based solution, this version looks pretty straightforward.

Update

A lens-based solution is certainly possible. Here is one such:

var transform = over(
  lensProp('participants'), 
  map(view(lensPath(['entity', 'uid'])))
)

var listObjects = {participants: [{entity: {uid: 1}}, {entity: {uid: 2}}]}

console.log(transform(listObjects))

<script src="https://bundle.run/[email protected]"></script><script>
const {over, lensProp, map, view, lensPath} = ramda  </script>

edited Mar 31, 2019 at 19:32

answered Mar 31, 2019 at 19:24

Scott Sauyet

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Comments

dmitrydwhite · Accepted Answer · 2019-03-31 19:35:00Z

2

Also could use just pure JavaScript es6:

const uidArray = listObjects.participants.map(({ entity: { uid } }) => uid);

answered Mar 31, 2019 at 19:35

dmitrydwhite

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Comments

Nino Filiu · Accepted Answer · 2019-03-31 19:32:50Z

0

Well, you can do it in Ramda, but you can simply use VanillaJS™ for that and have a fast, one-line, library-free solution:

const obj = {
  participants: [
    {entity: {uid: 1}},
    {entity: {uid: 2}}
  ]
}
obj.participants = obj.participants.map(p => p.entity.uid);
console.log(obj);

answered Mar 31, 2019 at 19:32

Nino Filiu

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3 Comments

Scott Sauyet Over a year ago

Just so you know, someone looking for a Ramda solution probably is not interested in a technique that modifies the input. Of course this could easily be fixed up not to do that.

Nino Filiu Over a year ago

I don't really know the philosophy of Ramda, thanks for the input! I just went for the simplest solution that fitted the OP's requirements

Hitmands Over a year ago

to fit the Op's requirements you needed to use ramda... Mutating the input is non an option in fp.

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