const assert = require('assert');

const isPrime = (n) => {
  if (n <= 1) return false
  else if (n <= 3) return true
  else if (n % 2 === 0 || n % 3 === 0) return false

  let i = 5;
  while (i * i <= n) {
    if(n % i === 0 || n % (i + 2) === 0) return false
    i += 6
  }
  return true;
}

const count = (array, n) => {
  const filtered = array.filter(a => a === n);
  console.log(n, filtered, filtered.length);
  return filtered.length;
}

const filter = (fst, snd) => {
  return fst.reduce((acc, a) => {
    if(isPrime(count(snd, a)))
      return acc

    return acc.concat(a);
  }, [])
}

const a = [2,3,9,2,5,1,3,7,10]
const b = [2,1,3,4,3,10,6,6,1,7,10,10,10]
const c = [2,9,2,5,7,10]
assert.deepEqual(filter(a, b), c)