<button id="btn">たたけ！</button>
<p id="score">0</p>
#btn {
font-size: 2rem;
padding: 20px 40px;
cursor: pointer;
}
#score {
font-size: 3rem;
font-weight: bold;
}
const btn = document.querySelector('#btn');
const score = document.querySelector('#score');
let count = 0;
btn.addEventListener('click', function() {
count = count + 1;
score.textContent = count;
if(count === 3) {
score.textContent = 'クリア！';
}
});