如何在复选框中选中时显示下拉菜单

<input type="checkbox" id="checkbox" onchange="toggleDropdown()">
<select id="dropdown" style="display: none;">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

function toggleDropdown() {
  var checkbox = document.getElementById("checkbox");
  var dropdown = document.getElementById("dropdown");
  
  if (checkbox.checked) {
    dropdown.style.display = "block";
  } else {
    dropdown.style.display = "none";
  }
}

#checkbox {
  /* Add styles for checkbox */
}

#dropdown {
  /* Add styles for dropdown */
}