js获取下拉框所有值

<!-- 单选下拉框 -->
<select id="singleSelect">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

<!-- 多选下拉框 -->
<select id="multiSelect" multiple>
  <option value="multi1">Multi Option 1</option>
  <option value="multi2">Multi Option 2</option>
  <option value="multi3">Multi Option 3</option>
</select>

<button onclick="getSelectValues()">获取值</button>

function getSelectValues() {
  // 获取单选下拉框的值
  var singleSelect = document.getElementById('singleSelect');
  var singleValue = singleSelect.options[singleSelect.selectedIndex].value;
  console.log('单选下拉框的值:', singleValue);

  // 获取多选下拉框的所有值
  var multiSelect = document.getElementById('multiSelect');
  var multiValues = [];
  for (var i = 0; i < multiSelect.options.length; i++) {
    if (multiSelect.options[i].selected) {
      multiValues.push(multiSelect.options[i].value);
    }
  }
  console.log('多选下拉框的值:', multiValues);
}