根据从下拉菜单中选择的选项更新JS中的变量

<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>

var dropdown = document.getElementById("dropdown");
var selectedOption = dropdown.value;

var updatedVariable;

switch (selectedOption) {
  case "option1":
    updatedVariable = "新的值1";
    break;
  case "option2":
    updatedVariable = "新的值2";
    break;
  case "option3":
    updatedVariable = "新的值3";
    break;
  default:
    updatedVariable = "默认值";
    break;
}