<button class="click-count">click me</button>
<button class="click-count">click me</button>
<button class="click-count">click me</button>
document.addEventListener('click', ({ target: t }) => {
if (t.classList.contains('click-count')) {
t.innerText = (t.innerText | 0) + 1;
}
});
// или
const onClick = e => e.target.textContent = -~e.target.textContent;
document.querySelectorAll('.click-count').forEach(n => n.addEventListener('click', onClick));