<div style="width: 100px; height: 100px; background: pink;">
  <button type="button">
    warning
  </button>
</div>

<script>
  document
    .querySelector('div')
    .addEventListener(
      'click',
      (event) => {
        if (event.eventPhase === 2) {
          return window.alert('div 自己触发的');
        }
        return window.alert('div 的子元素触发的');
      },
    );
</script>