js设置select默认选中值

<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>
  // 假设我们要将值为"2"的选项设置为默认选中
  document.addEventListener("DOMContentLoaded", function() {
    var selectElement = document.getElementById("mySelect");
    var options = selectElement.options;
    
    for (var i = 0; i < options.length; i++) {
      if (options[i].value === "2") {
        options[i].selected = true;
        break;
      }
    }
  });
</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"; // 直接设置value也可以达到选中效果
    }
  });
</script>