How do I remove an object if it contains a key with an empty array?

Question

I have an an array of objects. My objective is to remove objects that contain keys with empty arrays.

I am using ramda, but am hitting a wall at the moment.

const myData = {
  "one": {
    "two": {
      "id": "1",
      "three": [{
        "id": "33",
        "copy": [{
            "id": "1",
            "text": "lorem",
            "answer": [],
          },
          {
            "id": "2",
            "text": "ipsum",
            "answer": [{
              "id": 1,
              "class": "science"
            }]
          },
          {
            "id": "3",
            "text": "baesun",
            "answer": [{
              "id": 2,
              "class": "reading"
            }]
          }
        ],
      }]
    }

  }
}

flatten(pipe(
    path(['one', 'two', 'three']),
    map(step => step.copy.map(text => ({
      answers: text.answer.map(answer => ({
        class: answer.class,
      })),
    }), ), ))
  (myData))

This the result:

[{"answers": []}, {"answers": [{"class": "science"}]}, {"answers": [{"class": "reading"}]}]

This is the expectation:

[{"answers": [{"class": "science"}]}, {"answers": [{"class": "reading"}]}]

Answer 1

Get the the array of inside three with path, chain the arrays inside the copy properties, and project them to contain only answer . Reject empty answers, and then evolve the objects inside each answer to contain only the class property.

 const {pipe, path, chain, prop, project, reject, propSatisfies, isEmpty, map, evolve} = ramda const transform = pipe( path(['one', 'two', 'three']), // get the array chain(prop('copy')), // concat the copy to a single array project(['answer']), // extract the answers reject(propSatisfies(isEmpty, 'answer')), // remove empty answers map(evolve({ answer: project(['class']) })) // convert the objects inside each answer to contain only class ) const data = {"one":{"two":{"id":"1","three":[{"id":"33","copy":[{"id":"1","text":"lorem","answer":[]},{"id":"2","text":"ipsum","answer":[{"id":1,"class":"science"}]},{"id":"3","text":"baesun","answer":[{"id":2,"class":"reading"}]}]}]}}} const result = transform(data) console.log(result) 

 <script src="//bundle.run/ramda@0.26.1"></script> 

Answer 2

use filter

 const filter = R.filter, flatten = R.flatten, pipe = R.pipe, path = R.path, map = R.map; const myData = { "one": { "two": { "id": "1", "three": [{ "id": "33", "copy": [{ "id": "1", "text": "lorem", "answer": [], }, { "id": "2", "text": "ipsum", "answer": [{ "id": 1, "class": "science" }] }, { "id": "3", "text": "baesun", "answer": [{ "id": 2, "class": "reading" }] } ], }] } } } const result = filter(answersObj => answersObj.answers.length, flatten(pipe( path(['one', 'two', 'three']), map(step => step.copy.map(text => ({ answers: text.answer.map(answer => ({ class: answer.class, })) }))) )(myData))) console.log(result); 

 <script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.min.js"></script>