Ramda - Get one array from multiple objects

Question

I am trying to extract array of nodes from multiple objects using ramda.

Sample data:

const testData = {
  "117590": {
    "id": 117590,
    "nodes": [
      117864,
      117865,
      117866
    ]
  },
  "117591": {
    "id": 117591,
    "nodes": [
      117867,
      117868
    ]
  }
}

I tried to use such query: R.pluck('nodes', testData); But as a result I got:

{"117590": [117864, 117865, 117866], "117591": [117867, 117868]}

How to combine all nodes in one array? Here is my Ramda editor link

Ori Drori · Accepted Answer · 2020-12-07 21:56:18Z

3

Option 1: Convert to array using R.values, and then pluck and flatten results.

Option 2: Use R.values, and then get the nodes and flatten using R.chain with R.prop.

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

const fn1 = pipe(values, pluck('nodes'), flatten)
const fn2 = pipe(values, chain(prop('nodes')))

const testData = {"117590":{"id":117590,"nodes":[117864,117865,117866]},"117591":{"id":117591,"nodes":[117867,117868]}}

console.log(fn1(testData))

console.log(fn2(testData))

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.1/ramda.min.js" integrity="sha512-rZHvUXcc1zWKsxm7rJ8lVQuIr1oOmm7cShlvpV0gWf0RvbcJN6x96al/Rp2L2BI4a4ZkT2/YfVe/8YvB2UHzQw==" crossorigin="anonymous"></script>

answered Dec 7, 2020 at 21:56

Ori Drori

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2 Comments

omygoodness Over a year ago

Thank you. Both solutions are working but could you tell me which one is more efficient? I would like to use it with large set of objects.

Ori Drori Over a year ago

The 2nd one should be more efficient (less loops). I haven't profiled but it usually doesn't really matter unless you have more than 20k objects.

Scott Sauyet · Accepted Answer · 2020-12-07 21:56:55Z

1

Just think about it in two steps. First get the values of the object, and then take their node properties. The simplest way to get those nodes is to use chain (prop ('node')). The two steps can be combined with pipe or compose.

const getNodes = pipe (values, chain(prop('nodes')))

const testData = {117590: {id: 117590, nodes: [117864, 117865, 117866]}, 117591: {id: 117591, nodes: [117867, 117868]}}

console .log (getNodes (testData))

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.1/ramda.min.js"></script>
<script> const {pipe, values, chain, prop} = R                                 </script>

answered Dec 7, 2020 at 21:56

Scott Sauyet

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