CODEWITHSUNDEEP
javascriptarraysramda.js
Kristina Frolkova
Kristina Frolkova

Reputation: 31

How do I count duplicates in an array with Ramda?

I have an array with duplicate values and I need to find out how many times each value occurs in the array using ramda.js.

This is my array: [2013, 2013, 2013, 2014, 2014, 2014, 2014, 2015, 2015, 2015, 2015, 2015, 2015, 2015, 2016, 2016, 2016, 2016, 2016, 2017, 2017, 2017]

This is what I want to get out of it: [3, 4, 7, 5, 3]

Here's an example of how it might work in pure JavaScript.

function count (arr) {
  const counts = {}
  arr.forEach((x) => { counts[x] = (counts[x] || 0) + 1 })
  return Object.values(counts)
}

Upvotes: 3

Views: 2512

Answers (1)

Ori Drori
Ori Drori

Reputation: 191976

Assuming that (like in your code) the duplicates don't have to be in sequence, you can get the same results with R.countBy() and R.values():

const { pipe, countBy, identity, values } = R;

const arr = [2013, 2013, 2013, 2014, 2014, 2014, 2014, 2015, 2015, 2015, 2015, 2015, 2015, 2015, 2016, 2016, 2016, 2016, 2016, 2017, 2017, 2017]

const countDupes = pipe(
  countBy(identity),
  values
)

console.log(countDupes(arr));
<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>

Upvotes: 6

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