如何使用ramda.js将对象数组转换为整数数组，以从这些对象中提取值？

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

Answer 1

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/ramda@0.26.1"></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/ramda@0.26.1"></script><script> const {over, lensProp, map, view, lensPath} = ramda </script> 

Answer 2

也可以只使用纯JavaScript es6：

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

Answer 3

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);