How do you keep the every kth element of a list in Ramda?

How do you filter out every kth element of a list with Ramda?

input = [1, 2, 3, 4, 5, 6, 7, 8, 9]

output = keepKth(input, 3)

output = [1, 4, 7]

Solution 1:

This seemed to work:

  let k = 3;
  let Kth = (value, index) => (index % k == 0)
  let filterKth = R.addIndex(R.filter)(Kth);

  let input = [1, 2, 3, 4, 5, 6, 7, 8, 9];
  let output = filterKth(input);

Solution 2:

A variation based on Scott's comment:

const keepEvery = k => compose(pluck(0), splitEvery(k));

keepEvery(3)([1, 2, 3, 4, 5, 6, 7, 8, 9]);
//=> [1, 4, 7]

• https://ramdajs.com/docs/#pluck
• https://ramdajs.com/docs/#splitEvery