const $input = document.querySelector('#input'); 
const $form = document.querySelector('#form'); 
const $logs = document.querySelector('#logs');
const numbers = [];
for (let n = 1; n <= 9; n += 1) { 
  numbers.push(n);
}

const answer = []; -------------------------------------------------- ① 
for (let n = 0; n <= 3; n += 1) { // 4번 반복 ----------------------- ② 
  const index = Math.floor(Math.random() * 9); // 0~8 정수 뽑기 ----- ③ 
  answer.push(numbers[index]); -------------------------------------- ④ 
  numbers.splice(index, 1); ----------------------------------------- ⑤ 
} 
console.log(answer);