<select id="selectOption">
  <option value="div1">选项1</option>
  <option value="div2">选项2</option>
  <option value="div3">选项3</option>
</select>

<div id="div1" style="display: none;">这是div1</div>
<div id="div2" style="display: none;">这是div2</div>
<div id="div3" style="display: none;">这是div3</div>

document.getElementById("selectOption").addEventListener("change", function() {
  var selectedValue = this.value;
  
  // 隐藏所有的div
  var divs = document.getElementsByTagName("div");
  for (var i = 0; i < divs.length; i++) {
    divs[i].style.display = "none";
  }
  
  // 显示选中的div
  document.getElementById(selectedValue).style.display = "block";
});