基于复选框单击和取消单击重置下拉菜单

<input type="checkbox" id="checkbox" onclick="resetDropdown()">
<select id="dropdown">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

function resetDropdown() {
  var checkbox = document.getElementById("checkbox");
  var dropdown = document.getElementById("dropdown");
  
  if (checkbox.checked) {
    dropdown.selectedIndex = 0; // 重置下拉菜单为第一个选项
    dropdown.disabled = true; // 禁用下拉菜单
  } else {
    dropdown.disabled = false; // 启用下拉菜单
  }
}

<input type="checkbox" id="checkbox" onclick="resetDropdown()">