使下拉列表的内容居中

<select id="myDropdown">
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

#myDropdown {
  text-align: center;
}

#myDropdown option {
  text-align: center;
}

var dropdown = document.getElementById("myDropdown");
var options = dropdown.getElementsByTagName("option");
for (var i = 0; i < options.length; i++) {
  options[i].style.textAlign = "center";
}