Ramda - how to get nested array values

Question

I am trying to get values from nested arrays using Ramda. I have multiple groups like in the example below. I need to get all children from all sections and all childrenWithoutSections in one array of strings.

const groups = [
   {
      "id":"10",
      "sections":[
         {
            "id":"1",
            "children":["10", "11"]
         },
         {
            "id":"2",
            "children":["12"]
         }
      ],
      "childrenWithoutSections":["1", "2"]
   },
   {
      "id":"11",
      "sections":[
         {
            "id":"3",
            "children":["13", "14"]
         },
         {
            "id":"4",
            "children":["15"]
         }
      ],
      "childrenWithoutSections":["3", "4"]
   }
]

I started with something like this:

R.pipe(
  R.pluck(['childrenWithoutSections']),
  R.flatten
)(groups)

And as a result, I got all the children from one required key but I have no idea how to get nested values from sections/children?

Anything wrong with simply doing groups .flatMap (g => [... g .sections .flatMap (s => s.children), ... g . childrenWithoutSections]) ? — Scott Sauyet
– Scott Sauyet, Commented Jan 12, 2022 at 20:12
Unfortunately, I need to support IE11 :/ Probably I can find some polyfills to use it there but using Ramda is easier. — omygoodness
– omygoodness, Commented Jan 12, 2022 at 20:17
This is similar: R .chain (g => R .chain (s => s.children, g .sections) .concat (g . childrenWithoutSections), groups) — Scott Sauyet
– Scott Sauyet, Commented Jan 12, 2022 at 20:29

Scott Sauyet · Accepted Answer · 2022-01-12 21:32:30Z

2

As well as the suggestions in the comments, we can also write a point-free version of this:

const extract = chain (
  lift (concat) (
    pipe (prop ('sections'), pluck ('children'), flatten), 
    prop ('childrenWithoutSections')
  )
)

const groups = [{id: "10", sections: [{id: "1", children: ["10", "11"]}, {id: "2", children: ["12"]}], childrenWithoutSections: ["1", "2"]}, {id: "11", sections: [{id: "3", children: ["13", "14"]}, {id: "4", children: ["15"]}], childrenWithoutSections: ["3", "4"]}]

console .log (extract (groups))

.as-console-wrapper {max-height: 100% !important; top: 0}

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.27.2/ramda.min.js"></script>
<script> const {chain, lift, concat, pipe, prop, pluck, flatten} = R     </script>

edited Jan 12, 2022 at 21:32

answered Jan 12, 2022 at 20:42

Scott Sauyet

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1 Comment

omygoodness Over a year ago

As always exactly what I needed. Thank you for your help.

Ori Drori · Accepted Answer · 2022-01-12 21:03:09Z

2

Another option is to use R.juxt to get children from the sections, and the childrenWithoutSections and then flattening the results. By chaining the results we get the array of values.

const {chain, pipe, juxt, prop, pluck, flatten } = R 

const fn = chain(pipe(
  juxt([
    pipe(prop('sections'), pluck('children')),
    prop('childrenWithoutSections')
  ]),
  flatten,
))

const groups = [{id: "10", sections: [{id: "1", children: ["10", "11"]}, {id: "2", children: ["12"]}], childrenWithoutSections: ["1", "2"]}, {id: "11", sections: [{id: "3", children: ["13", "14"]}, {id: "4", children: ["15"]}], childrenWithoutSections: ["3", "4"]}]

const result = fn(groups)

console.log(result)

.as-console-wrapper {max-height: 100% !important; top: 0}

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.27.2/ramda.min.js"></script>

answered Jan 12, 2022 at 21:03

Ori Drori

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2 Comments

Scott Sauyet Over a year ago

Nice! There's so often more than one good way to do these things.

omygoodness Over a year ago

I must say you two always have great ways to do these things... So thank you both :)

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