<div id="buttons"> <!-- Step 1 -->
  <button class="buttonClass">Click me</button>
  <button class="buttonClass">Click me</button>
  <!-- buttons... -->
  <button class="buttonClass">Click me</button>
</div>
<script>
  document.getElementById('buttons')
    .addEventListener('click', event => { // Step 2
      if (event.target.className === 'buttonClass') { // Step 3
        console.log('Click!');
      }
    });
</script>