js设置下拉框默认选中的值

<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2" selected>Option 2</option> <!-- 默认选中 -->
  <option value="3">Option 3</option>
</select>

<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
  <option value="3">Option 3</option>
</select>

<script>
  // 假设我们想设置值为"2"的选项为默认选中
  document.addEventListener("DOMContentLoaded", function() {
    var selectElement = document.getElementById("mySelect");
    selectElement.value = "2"; // 设置默认选中的值
  });
</script>

<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2">Option 2</option>
  <option value="3">Option 3</option>
</select>

<script>
  document.addEventListener("DOMContentLoaded", function() {
    var selectElement = document.getElementById("mySelect");
    if (selectElement) {
      selectElement.value = "2"; // 确保元素存在后再设置值
    }
  });
</script>