根据下拉列表中选定的值切换<div>

<select id="dropdown">
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
</select>

<div id="content1" style="display: none;">
  这是选项1对应的内容
</div>

<div id="content2" style="display: none;">
  这是选项2对应的内容
</div>

<div id="content3" style="display: none;">
  这是选项3对应的内容
</div>

document.getElementById("dropdown").addEventListener("change", function() {
  var selectedValue = this.value;
  
  // 隐藏所有内容
  document.getElementById("content1").style.display = "none";
  document.getElementById("content2").style.display = "none";
  document.getElementById("content3").style.display = "none";
  
  // 根据选定的值显示对应的内容
  if (selectedValue === "option1") {
    document.getElementById("content1").style.display = "block";
  } else if (selectedValue === "option2") {
    document.getElementById("content2").style.display = "block";
  } else if (selectedValue === "option3") {
    document.getElementById("content3").style.display = "block";
  }
});