const changeComputerHand = () => {
  (중략)
}

①

let intervalId = setInterval(changeComputerHand, 50); 
const clickButton = () => {
  clearInterval(intervalId);
 // 점수 계산 및 화면 표시
  setTimeout(() => {
    intervalId = setInterval(changeComputerHand, 50);
  }, 1000); 
};

②

$rock.addEventListener('click', clickButton); 
$scissors.addEventListener('click', clickButton); 
$paper.addEventListener('click', clickButton);