$form.addEventListener('submit', (event) => { 
  (중략)
  console.log(winBalls, bonus);

  setTimeout(() => { ------------------------------- ①
    const $ball = document.createElement('div'); --- ②
    $ball.className = 'ball'; ---------------------- ③
    $ball.textContent = winBalls[0]; --------------- ④
    $result.appendChild($ball); -------------------- ⑤
  }, 1000);

});