[JavaScript] 프로그래머스 소수 찾기 LEVEL2

문제출처

const permutation = (arr, selectNum) => {
  let result = [];
  if (selectNum === 1) return arr.map((v) => [v]);

  arr.forEach((v, idx, arr) => {
    const fixer = v;
    const restArr = arr.filter((_, index) => index !== idx);
    const permuationArr = permutation(restArr, selectNum - 1);
    const combineFixer = permuationArr.map((v) => [fixer, ...v]);
    result.push(...combineFixer);
  });
  return result;
};

const isPrime = (num) => {
    if (num === 1 || num === 0) return false;
    if (num === 2) return true;
    for (let i=2; i<num/2 + 1; i++) {
        if (num % i === 0) return false;
    }
    return true;
};

function solution(numbers) {
    let answer = 0;
    const arr = numbers.split('');
    const set = new Set();
    
    for (let i=1; i<=numbers.length; i++) {
        const result = permutation(arr, i).map(res => +res.join(''));
        result.forEach(res => {
            if (!set.has(res)) {
                set.add(res);
                answer += isPrime(res) ? 1 : 0;
            }
        });
    }
    
    return answer;
}