js select添加属性值

<select id="mySelect">
  <option value="1" data-custom="A">Option 1</option>
  <option value="2" data-custom="B">Option 2</option>
  <option value="3" data-custom="C">Option 3</option>
</select>

// 获取select元素
var selectElement = document.getElementById('mySelect');

// 创建一个新的option元素
var newOption = document.createElement('option');
newOption.value = '4';
newOption.text = 'Option 4';
newOption.setAttribute('data-custom', 'D'); // 添加自定义属性

// 将新的option元素添加到select元素中
selectElement.appendChild(newOption);

window.onload = function() {
  var selectElement = document.getElementById('mySelect');
  var newOption = document.createElement('option');
  newOption.value = '4';
  newOption.text = 'Option 4';
  newOption.setAttribute('data-custom', 'D');
  selectElement.appendChild(newOption);
};