获取动态填充的下拉列表的旧选定值

// HTML代码
<select id="mySelect">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

// JavaScript代码
var selectElement = document.getElementById("mySelect");
var previousValue = null;

selectElement.addEventListener("change", function() {
  previousValue = selectElement.value;
});

selectElement.addEventListener("click", function() {
  selectElement.value = previousValue;
});

// HTML代码
<select id="mySelect">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

// JavaScript代码
var selectElement = document.getElementById("mySelect");

selectElement.addEventListener("change", function() {
  localStorage.setItem("selectedValue", selectElement.value);
});

window.addEventListener("load", function() {
  var previousValue = localStorage.getItem("selectedValue");
  if (previousValue) {
    selectElement.value = previousValue;
  }
});