JS filter elements

filterFn.js

/**
  https://www.hackerrank.com/challenges/filter-elements/problem
  ------
  Given a list of N integers A = [a1, a2, ..., aN], you have to 
  find those integers which are repeated at least K times. 
  In case no such element exists you have to print -1.

  If there are multiple elements in A which are repeated at least K times, 
  then print these elements ordered by their first occurrence in the list.
*/

const filterFn = (nums, k) => {
  const result = nums.reduce((acc, num, index) => {
    const numInArray = nums.filter(n => n === num);
    if (!acc[num] && numInArray.length >= k) {
      acc[num] = { count: numInArray.length, index };
    }
    return acc;
  }, {});
  const entries = Object.entries(result);
  return entries.length === 0
    ? '-1'
    : entries
        .sort((a, b) => a[1].index - b[1].index)
        .map(x => x[0])
        .join(' ');
};

const nums = [4, 5, 2, 5, 4, 3, 1, 3, 4];
let k = 2;

filterFn(nums, k);
// "4 5 3"

k = 3;
filterFn(nums, k);
// "-1"