如何在angular的下拉列表中遮盖选择

<select>
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

.select-overlay {
  position: relative;
  z-index: 1;
}

.select-overlay::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 2;
  pointer-events: none;
}

<select class="select-overlay">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>