显示嵌套下拉列表，并将溢出隐藏设置为父级下拉列表

<div class="parent-dropdown">
  <select id="parent-select">
    <option value="">请选择</option>
    <option value="option1">选项1</option>
    <option value="option2">选项2</option>
    <option value="option3">选项3</option>
  </select>
  <div class="child-dropdown">
    <select id="child-select">
      <option value="">请选择</option>
      <option value="child-option1">子选项1</option>
      <option value="child-option2">子选项2</option>
      <option value="child-option3">子选项3</option>
    </select>
  </div>
</div>

.parent-dropdown {
  position: relative;
}

.child-dropdown {
  position: absolute;
  top: 100%;
  left: 0;
  display: none;
}

.parent-dropdown:hover .child-dropdown {
  display: block;
  overflow: hidden;
}

$(document).ready(function() {
  $('#parent-select').change(function() {
    var selectedOption = $(this).val();
    if (selectedOption === 'option1') {
      // 根据选择的父级选项显示对应的子级选项
      $('#child-select').html('<option value="">请选择</option><option value="child-option1">子选项1</option>');
    } else if (selectedOption === 'option2') {
      $('#child-select').html('<option value="">请选择</option><option value="child-option2">子选项2</option>');
    } else if (selectedOption === 'option3') {
      $('#child-select').html('<option value="">请选择</option><option value="child-option3">子选项3</option>');
    } else {
      $('#child-select').html('<option value="">请选择</option>');
    }
  });
});