function solution(s) { return (s.length === 4 || s.length === 6) && (s.split('').every(s => !isNaN(s))); }
function alpha_string46(s){ var regex = /^\d{6}$|^\d{4}$/; return regex.test(s); }
하.. 정말 외계어네ㅋㅋㅋㅋㅋㅋ