js 动态获取下拉菜单id

<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
</select>

// 直接通过ID获取元素
var selectElement = document.getElementById('mySelect');
console.log(selectElement.id); // 输出: mySelect

<select class="dynamic-select">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
</select>
<select class="dynamic-select">
  <option value="3">Option 3</option>
  <option value="4">Option 4</option>
</select>

// 通过类名获取所有匹配的元素
var selectElements = document.getElementsByClassName('dynamic-select');
for (var i = 0; i < selectElements.length; i++) {
  console.log(selectElements[i].id); // 输出每个select元素的ID
}

// 或者通过标签名获取
var selectElementsByTag = document.getElementsByTagName('select');
for (var i = 0; i < selectElementsByTag.length; i++) {
  console.log(selectElementsByTag[i].id); // 输出每个select元素的ID
}

<select id="dynamicSelect">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
</select>

// 添加事件监听器
document.getElementById('dynamicSelect').addEventListener('change', function() {
  console.log(this.id); // 输出: dynamicSelect
});